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1.
Environ Microbiol ; 26(5): e16638, 2024 May.
Artigo em Inglês | MEDLINE | ID: mdl-38733104

RESUMO

Plasmids, despite their critical role in antibiotic resistance and modern biotechnology, are understood in only a few bacterial groups in terms of their natural ecological dynamics. The bacterial phylum Planctomycetes, known for its unique molecular and cellular biology, has a largely unexplored plasmidome. This study offers a thorough exploration of the diversity of natural plasmids within Planctomycetes, which could serve as a foundation for developing various genetic research tools for this phylum. Planctomycetes plasmids encode a broad range of biological functions and appear to have coevolved significantly with their host chromosomes, sharing many homologues. Recent transfer events of insertion sequences between cohabiting chromosomes and plasmids were also observed. Interestingly, 64% of plasmid genes are distantly related to either chromosomally encoded genes or have homologues in plasmids from other bacterial groups. The planctomycetal plasmidome is composed of 36% exclusive proteins. Most planctomycetal plasmids encode a replication initiation protein from the Replication Protein A family near a putative iteron-containing replication origin, as well as active type I partition systems. The identification of one conjugative and three mobilizable plasmids suggests the occurrence of horizontal gene transfer via conjugation within this phylum. This comprehensive description enhances our understanding of the plasmidome of Planctomycetes and its potential implications in antibiotic resistance and biotechnology.


Assuntos
Transferência Genética Horizontal , Plasmídeos , Plasmídeos/genética , Bactérias/genética , Bactérias/classificação , Proteínas de Bactérias/genética , Conjugação Genética , Filogenia , Planctomycetales/genética , Evolução Molecular , Origem de Replicação/genética
2.
Commun Biol ; 7(1): 519, 2024 May 02.
Artigo em Inglês | MEDLINE | ID: mdl-38698198

RESUMO

DNA replication is essential for the proliferation of all cells. Bacterial chromosomes are replicated bidirectionally from a single origin of replication, with replication proceeding at about 1000 bp per second. For the model organism, Escherichia coli, this translates into a replication time of about 40 min for its 4.6 Mb chromosome. Nevertheless, E. coli can propagate by overlapping replication cycles with a maximum short doubling time of 20 min. The fastest growing bacterium known, Vibrio natriegens, is able to replicate with a generation time of less than 10 min. It has a bipartite genome with chromosome sizes of 3.2 and 1.9 Mb. Is simultaneous replication from two origins a prerequisite for its rapid growth? We fused the two chromosomes of V. natriegens to create a strain carrying one chromosome with a single origin of replication. Compared to the parental, this strain showed no significant deviation in growth rate. This suggests that the split genome is not a prerequisite for rapid growth.


Assuntos
Cromossomos Bacterianos , Replicação do DNA , Vibrio , Vibrio/genética , Cromossomos Bacterianos/genética , Genoma Bacteriano , Origem de Replicação , DNA Bacteriano/genética , DNA Bacteriano/metabolismo
3.
PLoS One ; 19(5): e0301172, 2024.
Artigo em Inglês | MEDLINE | ID: mdl-38696408

RESUMO

Horizontal gene transfer (HGT) is a powerful evolutionary force that considerably shapes the structure of prokaryotic genomes and is associated with genomic islands (GIs). A GI is a DNA segment composed of transferred genes that can be found within a prokaryotic genome, obtained through HGT. Much research has focused on detecting GIs in genomes, but here we pursue a new course, which is identifying possible preferred locations of GIs in the prokaryotic genome. Here, we identify the locations of the GIs within prokaryotic genomes to examine patterns in those locations. Prokaryotic GIs were analyzed according to the genome structure that they are located in, whether it be a circular or a linear genome. The analytical investigations employed are: (1) studying the GI locations in relation to the origin of replication (oriC); (2) exploring the distances between GIs; and (3) determining the distribution of GIs across the genomes. For each of the investigations, the analysis was performed on all of the GIs in the data set. Moreover, to void bias caused by the distribution of the genomes represented, the GIs in one genome from each species and the GIs of the most frequent species are also analyzed. Overall, the results showed that there are preferred sites for the GIs in the genome. In the linear genomes, these sites are usually located in the oriC region and terminus region, while in the circular genomes, they are located solely in the terminus region. These results also showed that the distance distribution between the GIs is almost exponential, which proves that GIs have preferred sites within genomes. The oriC and termniuns are preferred sites for the GIs and a possible natural explanation for this could be connected to the content of the oriC region. Moreover, the content of the GIs in terms of its protein families was studied and the results demonstrated that the majority of frequent protein families are close to identical in each section.


Assuntos
Transferência Genética Horizontal , Ilhas Genômicas , Genoma Bacteriano , Genoma Arqueal , Origem de Replicação/genética , Células Procarióticas/metabolismo
4.
Genome Biol ; 25(1): 126, 2024 May 21.
Artigo em Inglês | MEDLINE | ID: mdl-38773641

RESUMO

BACKGROUND: DNA replication progression can be affected by the presence of physical barriers like the RNA polymerases, leading to replication stress and DNA damage. Nonetheless, we do not know how transcription influences overall DNA replication progression. RESULTS: To characterize sites where DNA replication forks stall and pause, we establish a genome-wide approach to identify them. This approach uses multiple timepoints during S-phase to identify replication fork/stalling hotspots as replication progresses through the genome. These sites are typically associated with increased DNA damage, overlapped with fragile sites and with breakpoints of rearrangements identified in cancers but do not overlap with replication origins. Overlaying these sites with a genome-wide analysis of RNA polymerase II transcription, we find that replication fork stalling/pausing sites inside genes are directly related to transcription progression and activity. Indeed, we find that slowing down transcription elongation slows down directly replication progression through genes. This indicates that transcription and replication can coexist over the same regions. Importantly, rearrangements found in cancers overlapping transcription-replication collision sites are detected in non-transformed cells and increase following treatment with ATM and ATR inhibitors. At the same time, we find instances where transcription activity favors replication progression because it reduces histone density. CONCLUSIONS: Altogether, our findings highlight how transcription and replication overlap during S-phase, with both positive and negative consequences for replication fork progression and genome stability by the coexistence of these two processes.


Assuntos
Replicação do DNA , RNA Polimerase II , Transcrição Gênica , RNA Polimerase II/metabolismo , Humanos , Fase S/genética , Dano ao DNA , Proteínas Mutadas de Ataxia Telangiectasia/metabolismo , Proteínas Mutadas de Ataxia Telangiectasia/genética , Genoma Humano , Origem de Replicação
5.
Nat Commun ; 15(1): 3594, 2024 Apr 27.
Artigo em Inglês | MEDLINE | ID: mdl-38678011

RESUMO

Recurrent DNA break clusters (RDCs) are replication-transcription collision hotspots; many are unique to neural progenitor cells. Through high-resolution replication sequencing and a capture-ligation assay in mouse neural progenitor cells experiencing replication stress, we unravel the replication features dictating RDC location and orientation. Most RDCs occur at the replication forks traversing timing transition regions (TTRs), where sparse replication origins connect unidirectional forks. Leftward-moving forks generate telomere-connected DNA double-strand breaks (DSBs), while rightward-moving forks lead to centromere-connected DSBs. Strand-specific mapping for DNA-bound RNA reveals co-transcriptional dual-strand DNA:RNA hybrids present at a higher density in RDC than in other actively transcribed long genes. In addition, mapping RNA polymerase activity uncovers that head-to-head interactions between replication and transcription machinery result in 60% DSB contribution to the head-on compared to 40% for co-directional. Taken together we reveal TTR as a fragile class and show how the linear interaction between transcription and replication impacts genome stability.


Assuntos
Quebras de DNA de Cadeia Dupla , Replicação do DNA , Instabilidade Genômica , Transcrição Gênica , Animais , Camundongos , Células-Tronco Neurais/metabolismo , DNA/metabolismo , DNA/genética , Origem de Replicação , Telômero/metabolismo , Telômero/genética , Centrômero/metabolismo , Centrômero/genética
6.
Elife ; 122024 Apr 03.
Artigo em Inglês | MEDLINE | ID: mdl-38567819

RESUMO

Based on experimentally determined average inter-origin distances of ~100 kb, DNA replication initiates from ~50,000 origins on human chromosomes in each cell cycle. The origins are believed to be specified by binding of factors like the origin recognition complex (ORC) or CTCF or other features like G-quadruplexes. We have performed an integrative analysis of 113 genome-wide human origin profiles (from five different techniques) and five ORC-binding profiles to critically evaluate whether the most reproducible origins are specified by these features. Out of ~7.5 million union origins identified by all datasets, only 0.27% (20,250 shared origins) were reproducibly obtained in at least 20 independent SNS-seq datasets and contained in initiation zones identified by each of three other techniques, suggesting extensive variability in origin usage and identification. Also, 21% of the shared origins overlap with transcriptional promoters, posing a conundrum. Although the shared origins overlap more than union origins with constitutive CTCF-binding sites, G-quadruplex sites, and activating histone marks, these overlaps are comparable or less than that of known transcription start sites, so that these features could be enriched in origins because of the overlap of origins with epigenetically open, promoter-like sequences. Only 6.4% of the 20,250 shared origins were within 1 kb from any of the ~13,000 reproducible ORC-binding sites in human cancer cells, and only 4.5% were within 1 kb of the ~11,000 union MCM2-7-binding sites in contrast to the nearly 100% overlap in the two comparisons in the yeast, Saccharomyces cerevisiae. Thus, in human cancer cell lines, replication origins appear to be specified by highly variable stochastic events dependent on the high epigenetic accessibility around promoters, without extensive overlap between the most reproducible origins and currently known ORC- or MCM-binding sites.


Assuntos
Complexo de Reconhecimento de Origem , Proteínas de Saccharomyces cerevisiae , Humanos , Complexo de Reconhecimento de Origem/genética , Complexo de Reconhecimento de Origem/metabolismo , Origem de Replicação/genética , Sítios de Ligação , Replicação do DNA/genética , Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/metabolismo , Cromossomos Humanos/metabolismo , DNA/metabolismo , Proteínas de Ciclo Celular/metabolismo
7.
Sci Rep ; 14(1): 7708, 2024 04 02.
Artigo em Inglês | MEDLINE | ID: mdl-38565932

RESUMO

Human RECQL4, a member of the RecQ helicase family, plays a role in maintaining genomic stability, but its precise function remains unclear. The N-terminus of RECQL4 has similarity to Sld2, a protein required for the firing of DNA replication origins in budding yeast. Consistent with this sequence similarity, the Xenopus laevis homolog of RECQL4 has been implicated in initiating DNA replication in egg extracts. To determine whether human RECQL4 is required for firing of DNA replication origins, we generated cells in which both RECQL4 alleles were targeted, resulting in either lack of protein expression (knock-out; KO) or expression of a full-length, mutant protein lacking helicase activity (helicase-dead; HD). Interestingly, both the RECQL4 KO and HD cells were viable and exhibited essentially identical origin firing profiles as the parental cells. Analysis of the rate of fork progression revealed increased rates in the RECQL4 KO cells, which might be indicative of decreased origin firing efficiency. Our results are consistent with human RECQL4 having a less critical role in firing of DNA replication origins, than its budding yeast homolog Sld2.


Assuntos
RecQ Helicases , Origem de Replicação , Animais , Humanos , RecQ Helicases/genética , RecQ Helicases/metabolismo , Replicação do DNA , Xenopus laevis/metabolismo , DNA/metabolismo
8.
Nat Commun ; 15(1): 2737, 2024 Mar 28.
Artigo em Inglês | MEDLINE | ID: mdl-38548820

RESUMO

Bacterial chromosomes are folded into tightly regulated three-dimensional structures to ensure proper transcription, replication, and segregation of the genetic information. Direct visualization of chromosomal shape within bacterial cells is hampered by cell-wall confinement and the optical diffraction limit. Here, we combine cell-shape manipulation strategies, high-resolution fluorescence microscopy techniques, and genetic engineering to visualize the shape of unconfined bacterial chromosome in real-time in live Bacillus subtilis cells that are expanded in volume. We show that the chromosomes predominantly exhibit crescent shapes with a non-uniform DNA density that is increased near the origin of replication (oriC). Additionally, we localized ParB and BsSMC proteins - the key drivers of chromosomal organization - along the contour of the crescent chromosome, showing the highest density near oriC. Opening of the BsSMC ring complex disrupted the crescent chromosome shape and instead yielded a torus shape. These findings help to understand the threedimensional organization of the chromosome and the main protein complexes that underlie its structure.


Assuntos
Bacillus subtilis , Segregação de Cromossomos , Bacillus subtilis/genética , Bacillus subtilis/metabolismo , Segregação de Cromossomos/genética , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Complexo de Reconhecimento de Origem/metabolismo , Replicação do DNA/genética , Cromossomos Bacterianos/genética , Cromossomos Bacterianos/metabolismo , DNA Bacteriano/metabolismo , Origem de Replicação
9.
Nucleic Acids Res ; 52(7): 3493-3509, 2024 Apr 24.
Artigo em Inglês | MEDLINE | ID: mdl-38442257

RESUMO

Gene-strand bias is a characteristic feature of bacterial genome organization wherein genes are preferentially encoded on the leading strand of replication, promoting co-orientation of replication and transcription. This co-orientation bias has evolved to protect gene essentiality, expression, and genomic stability from the harmful effects of head-on replication-transcription collisions. However, the origin, variation, and maintenance of gene-strand bias remain elusive. Here, we reveal that the frequency of inversions that alter gene orientation exhibits large variation across bacterial populations and negatively correlates with gene-strand bias. The density, distance, and distribution of inverted repeats show a similar negative relationship with gene-strand bias explaining the heterogeneity in inversions. Importantly, these observations are broadly evident across the entire bacterial kingdom uncovering inversions and inverted repeats as primary factors underlying the variation in gene-strand bias and its maintenance. The distinct catalytic subunits of replicative DNA polymerase have co-evolved with gene-strand bias, suggesting a close link between replication and the origin of gene-strand bias. Congruently, inversion frequencies and inverted repeats vary among bacteria with different DNA polymerases. In summary, we propose that the nature of replication determines the fitness cost of replication-transcription collisions, establishing a selection gradient on gene-strand bias by fine-tuning DNA sequence repeats and, thereby, gene inversions.


Assuntos
Bactérias , Replicação do DNA , Evolução Molecular , Genoma Bacteriano , Replicação do DNA/genética , Bactérias/genética , Bactérias/metabolismo , DNA Polimerase Dirigida por DNA/metabolismo , DNA Polimerase Dirigida por DNA/genética , Sequências Repetidas Invertidas , Origem de Replicação/genética , Transcrição Gênica , Instabilidade Genômica
10.
mBio ; 15(4): e0031924, 2024 Apr 10.
Artigo em Inglês | MEDLINE | ID: mdl-38441981

RESUMO

Trypanosoma cruzi is the etiologic agent of the most prevalent human parasitic disease in Latin America, Chagas disease. Its genome is rich in multigenic families that code for virulent antigens and are present in the rapidly evolving genomic compartment named Disruptive. DNA replication is a meticulous biological process in which flaws can generate mutations and changes in chromosomal and gene copy numbers. Here, integrating high-throughput and single-molecule analyses, we were able to identify Predominant, Flexible, and Dormant Orc1Cdc6-dependent origins as well as Orc1Cdc6-independent origins. Orc1Cdc6-dependent origins were found in multigenic family loci, while independent origins were found in the Core compartment that contains conserved and hypothetical protein-coding genes, in addition to multigenic families. In addition, we found that Orc1Cdc6 density is related to the firing of origins and that Orc1Cdc6-binding sites within fired origins are depleted of a specific class of nucleosomes that we previously categorized as dynamic. Together, these data suggest that Orc1Cdc6-dependent origins may contribute to the rapid evolution of the Disruptive compartment and, therefore, to the success of T. cruzi infection and that the local epigenome landscape is also involved in this process.IMPORTANCETrypanosoma cruzi, responsible for Chagas disease, affects millions globally, particularly in Latin America. Lack of vaccine or treatment underscores the need for research. Parasite's genome, with virulent antigen-coding multigenic families, resides in the rapidly evolving Disruptive compartment. Study sheds light on the parasite's dynamic DNA replication, discussing the evolution of the Disruptive compartment. Therefore, the findings represent a significant stride in comprehending T. cruzi's biology and the molecular bases that contribute to the success of infection caused by this parasite.


Assuntos
Doença de Chagas , Trypanosoma cruzi , Humanos , Trypanosoma cruzi/genética , Origem de Replicação , Doença de Chagas/parasitologia , Dosagem de Genes , Cromossomos
11.
Elife ; 122024 Feb 05.
Artigo em Inglês | MEDLINE | ID: mdl-38315099

RESUMO

Structural maintenance of chromosomes (SMC) complexes share conserved structures and serve a common role in maintaining chromosome architecture. In the bacterium Escherichia coli, the SMC complex MukBEF is necessary for rapid growth and the accurate segregation and positioning of the chromosome, although the specific molecular mechanisms involved are still unknown. Here, we used a number of in vivo assays to reveal how MukBEF controls chromosome conformation and how the MatP/matS system prevents MukBEF activity. Our results indicate that the loading of MukBEF occurs preferentially on newly replicated DNA, at multiple loci on the chromosome where it can promote long-range contacts in cis even though MukBEF can promote long-range contacts in the absence of replication. Using Hi-C and ChIP-seq analyses in strains with rearranged chromosomes, the prevention of MukBEF activity increases with the number of matS sites and this effect likely results from the unloading of MukBEF by MatP. Altogether, our results reveal how MukBEF operates to control chromosome folding and segregation in E. coli.


Assuntos
Proteínas de Escherichia coli , Escherichia coli , Escherichia coli/genética , Proteínas de Escherichia coli/genética , Proteínas Repressoras/genética , Cromossomos Bacterianos/genética , Origem de Replicação , Proteínas Cromossômicas não Histona/genética , Cromossomos , Segregação de Cromossomos
12.
Elife ; 122024 Feb 05.
Artigo em Inglês | MEDLINE | ID: mdl-38315095

RESUMO

There are approximately 500 known origins of replication in the yeast genome, and the process by which DNA replication initiates at these locations is well understood. In particular, these sites are made competent to initiate replication by loading of the Mcm replicative helicase prior to the start of S phase; thus, 'a site that binds Mcm in G1' might be considered to provide an operational definition of a replication origin. By fusing a subunit of Mcm to micrococcal nuclease, we previously showed that known origins are typically bound by a single Mcm double hexamer, loaded adjacent to the ARS consensus sequence (ACS). Here, we extend this analysis from known origins to the entire genome, identifying candidate Mcm binding sites whose signal intensity varies over at least three orders of magnitude. Published data quantifying single-stranded DNA (ssDNA) during S phase revealed replication initiation among the most abundant 1600 of these sites, with replication activity decreasing with Mcm abundance and disappearing at the limit of detection of ssDNA. Three other hallmarks of replication origins were apparent among the most abundant 5500 sites. Specifically, these sites: (1) appeared in intergenic nucleosome-free regions flanked on one or both sides by well-positioned nucleosomes; (2) were flanked by ACSs; and (3) exhibited a pattern of GC skew characteristic of replication initiation. We conclude that, if sites at which Mcm double hexamers are loaded can function as replication origins, then DNA replication origins are at least threefold more abundant than previously assumed, and we suggest that replication may occasionally initiate in essentially every intergenic region. These results shed light on recent reports that as many as 15% of replication events initiate outside of known origins, and this broader distribution of replication origins suggest that S phase in yeast may be less distinct from that in humans than widely assumed.


Assuntos
Proteínas de Saccharomyces cerevisiae , Saccharomyces cerevisiae , Humanos , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/metabolismo , Origem de Replicação , Replicação do DNA , Nucleossomos/metabolismo , Proteínas de Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/metabolismo , DNA Intergênico/metabolismo , Proteínas de Ciclo Celular/metabolismo
13.
mBio ; 15(4): e0320023, 2024 Apr 10.
Artigo em Inglês | MEDLINE | ID: mdl-38421162

RESUMO

The mechanisms underpinning the replication of genomic DNA have recently been challenged in Archaea. Indeed, the lack of origin of replication has no deleterious effect on growth, suggesting that replication initiation relies on homologous recombination. Recombination-dependent replication (RDR) appears to be based on the recombinase RadA, which is of absolute requirement when no initiation origins are detected. The origin of this flexibility in the initiation of replication and the extent to which it is used in nature are yet to be understood. Here, we followed the process of DNA replication throughout the growth stages of Thermococcus barophilus. We combined deep sequencing and genetics to elucidate the dynamics of oriC utilization according to growth phases. We discovered that in T. barophilus, the use of oriC diminishes from the lag to the middle of the log phase, and subsequently increases gradually upon entering the stationary phase. Although oriC demonstrates no indispensability, RadA does exhibit essentiality. Notably, a knockdown mutant strain provides confirmation of the pivotal role of RadA in RDR for the first time. Thus, we demonstrate the existence of a tight combination between oriC utilization and homologous recombination to initiate DNA replication along the growth phases. Overall, this study demonstrates how diverse physiological states can influence the initiation of DNA replication, offering insights into how environmental sensing might impact this fundamental mechanism of life. IMPORTANCE: Replication of DNA is highly important in all organisms. It initiates at a specific locus called ori, which serves as the binding site for scaffold proteins-either Cdc6 or DnaA-depending on the domain of life. However, recent studies have shown that the Archaea, Haloferax volcanii and Thermococcus kodakarensis could subsist without ori. Recombination-dependent replication (RDR), via the recombinase RadA, is the mechanism that uses homologous recombination to initiate DNA replication. The extent to which ori's use is necessary in natural growth remains to be characterized. In this study, using Thermococcus barophilus, we demonstrated that DNA replication initiation relies on both oriC and RDR throughout its physiological growth, each to varying degrees depending on the phase. Notably, a knockdown RadA mutant confirmed the prominent use of RDR during the log phase. Moreover, the study of ploidy in oriC and radA mutant strains showed that the number of chromosomes per cell is a critical proxy for ensuring proper growth and cell survival.


Assuntos
Thermococcus , Thermococcus/genética , Replicação do DNA , Recombinação Homóloga , DNA , Recombinases/genética , Origem de Replicação , Proteínas de Bactérias/genética
14.
PLoS Comput Biol ; 20(1): e1011753, 2024 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-38181054

RESUMO

Biological cells replicate their genomes in a well-planned manner. The DNA replication program of an organism determines the timing at which different genomic regions are replicated, with fundamental consequences for cell homeostasis and genome stability. In a growing cell culture, genomic regions that are replicated early should be more abundant than regions that are replicated late. This abundance pattern can be experimentally measured using deep sequencing. However, a general quantitative theory linking this pattern to the replication program is still lacking. In this paper, we predict the abundance of DNA fragments in asynchronously growing cultures from any given stochastic model of the DNA replication program. As key examples, we present stochastic models of the DNA replication programs in budding yeast and Escherichia coli. In both cases, our model results are in excellent agreement with experimental data and permit to infer key information about the replication program. In particular, our method is able to infer the locations of known replication origins in budding yeast with high accuracy. These examples demonstrate that our method can provide insight into a broad range of organisms, from bacteria to eukaryotes.


Assuntos
Replicação do DNA , Genoma , Replicação do DNA/genética , DNA , Genômica , Replicação Viral , Origem de Replicação/genética , Período de Replicação do DNA
15.
Nucleic Acids Res ; 52(2): 660-676, 2024 Jan 25.
Artigo em Inglês | MEDLINE | ID: mdl-38038269

RESUMO

Various origin mapping approaches have enabled genome-wide identification of origins of replication (ORI) in model organisms, but only a few studies have focused on divergent organisms. By employing three complementary approaches we provide a high-resolution map of ORIs in Plasmodium falciparum, the deadliest human malaria parasite. We profiled the distribution of origin of recognition complex (ORC) binding sites by ChIP-seq of two PfORC subunits and mapped active ORIs using NFS and SNS-seq. We show that ORIs lack sequence specificity but are not randomly distributed, and group in clusters. Licensing is biased towards regions of higher GC content and associated with G-quadruplex forming sequences (G4FS). While strong transcription likely enhances firing, active origins are depleted from transcription start sites. Instead, most accumulate in transcriptionally active gene bodies. Single molecule analysis of nanopore reads containing multiple initiation events, which could have only come from individual nuclei, showed a relationship between the replication fork pace and the distance to the nearest origin. While some similarities were drawn with the canonic eukaryote model, the distribution of ORIs in P. falciparum is likely shaped by unique genomic features such as extreme AT-richness-a product of evolutionary pressure imposed by the parasitic lifestyle.


Assuntos
Plasmodium falciparum , Origem de Replicação , Humanos , Sítios de Ligação , Mapeamento Cromossômico , Replicação do DNA , Genômica , Plasmodium falciparum/genética , Origem de Replicação/genética , Transcrição Gênica
16.
Nat Commun ; 14(1): 8049, 2023 Dec 11.
Artigo em Inglês | MEDLINE | ID: mdl-38081811

RESUMO

The mammalian DNA replication timing (RT) program is crucial for the proper functioning and integrity of the genome. The best-known mechanism for controlling RT is the suppression of late origins of replication in heterochromatin by RIF1. Here, we report that in antigen-activated, hypermutating murine B lymphocytes, RIF1 binds predominantly to early-replicating active chromatin and promotes early replication, but plays a minor role in regulating replication origin activity, gene expression and genome organization in B cells. Furthermore, we find that RIF1 functions in a complementary and non-epistatic manner with minichromosome maintenance (MCM) proteins to establish early RT signatures genome-wide and, specifically, to ensure the early replication of highly transcribed genes. These findings reveal additional layers of regulation within the B cell RT program, driven by the coordinated activity of RIF1 and MCM proteins.


Assuntos
Período de Replicação do DNA , Replicação do DNA , Animais , Camundongos , Cromatina/genética , Replicação do DNA/genética , Heterocromatina/genética , Mamíferos/genética , Proteínas de Manutenção de Minicromossomo/metabolismo , Origem de Replicação/genética , Proteínas de Ligação a Telômeros/metabolismo
17.
Nat Commun ; 14(1): 8339, 2023 Dec 14.
Artigo em Inglês | MEDLINE | ID: mdl-38097584

RESUMO

Genome duplication is essential for the proliferation of cellular life and this process is generally initiated by dedicated replication proteins at chromosome origins. In bacteria, DNA replication is initiated by the ubiquitous DnaA protein, which assembles into an oligomeric complex at the chromosome origin (oriC) that engages both double-stranded DNA (dsDNA) and single-stranded DNA (ssDNA) to promote DNA duplex opening. However, the mechanism of DnaA specifically opening a replication origin was unknown. Here we show that Bacillus subtilis DnaAATP assembles into a continuous oligomer at the site of DNA melting, extending from a dsDNA anchor to engage a single DNA strand. Within this complex, two nucleobases of each ssDNA binding motif (DnaA-trio) are captured within a dinucleotide binding pocket created by adjacent DnaA proteins. These results provide a molecular basis for DnaA specifically engaging the conserved sequence elements within the bacterial chromosome origin basal unwinding system (BUS).


Assuntos
Replicação do DNA , Proteínas de Ligação a DNA , Proteínas de Ligação a DNA/metabolismo , Proteínas de Bactérias/metabolismo , Origem de Replicação , Bactérias/genética , DNA , DNA de Cadeia Simples/genética , DNA Bacteriano/metabolismo , Cromossomos Bacterianos/genética , Cromossomos Bacterianos/metabolismo
18.
Nucleic Acids Res ; 51(22): 12303-12324, 2023 Dec 11.
Artigo em Inglês | MEDLINE | ID: mdl-37956271

RESUMO

Stochastic origin activation gives rise to significant cell-to-cell variability in the pattern of genome replication. The molecular basis for heterogeneity in efficiency and timing of individual origins is a long-standing question. Here, we developed Methylation Accessibility of TArgeted Chromatin domain Sequencing (MATAC-Seq) to determine single-molecule chromatin accessibility of four specific genomic loci. MATAC-Seq relies on preferential modification of accessible DNA by methyltransferases combined with Nanopore-Sequencing for direct readout of methylated DNA-bases. Applying MATAC-Seq to selected early-efficient and late-inefficient yeast replication origins revealed large heterogeneity of chromatin states. Disruption of INO80 or ISW2 chromatin remodeling complexes leads to changes at individual nucleosomal positions that correlate with changes in their replication efficiency. We found a chromatin state with an accessible nucleosome-free region in combination with well-positioned +1 and +2 nucleosomes as a strong predictor for efficient origin activation. Thus, MATAC-Seq identifies the large spectrum of alternative chromatin states that co-exist on a given locus previously masked in population-based experiments and provides a mechanistic basis for origin activation heterogeneity during eukaryotic DNA replication. Consequently, our single-molecule chromatin accessibility assay will be ideal to define single-molecule heterogeneity across many fundamental biological processes such as transcription, replication, or DNA repair in vitro and ex vivo.


Assuntos
Origem de Replicação , Saccharomyces cerevisiae , Cromatina/genética , DNA , Replicação do DNA , Nucleossomos/genética , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/metabolismo
19.
Nat Commun ; 14(1): 7489, 2023 Nov 18.
Artigo em Inglês | MEDLINE | ID: mdl-37980336

RESUMO

Bacterial chromosomes are dynamically and spatially organised within cells. In slow-growing Escherichia coli, the chromosomal terminus is initially located at the new pole and must therefore migrate to midcell during replication to reproduce the same pattern in the daughter cells. Here, we use high-throughput time-lapse microscopy to quantify this transition, its timing and its relationship to chromosome segregation. We find that terminus centralisation is a rapid discrete event that occurs ~25 min after initial separation of duplicated origins and ~50 min before the onset of bulk nucleoid segregation but with substantial variation between cells. Despite this variation, its movement is tightly coincident with the completion of origin segregation, even in the absence of its linkage to the divisome, suggesting a coupling between these two events. Indeed, we find that terminus centralisation does not occur if origin segregation away from mid-cell is disrupted, which results in daughter cells having an inverted chromosome organisation. Overall, our study quantifies the choreography of origin-terminus positioning and identifies an unexplored connection between these loci, furthering our understanding of chromosome segregation in this bacterium.


Assuntos
Proteínas de Escherichia coli , Escherichia coli , Escherichia coli/genética , Cromossomos , Proteínas de Escherichia coli/genética , Cromossomos Bacterianos/genética , Segregação de Cromossomos , Movimento Celular , Replicação do DNA , Origem de Replicação/genética
20.
Bioinformatics ; 39(11)2023 11 01.
Artigo em Inglês | MEDLINE | ID: mdl-37929975

RESUMO

MOTIVATION: The origins of replication sites (ORIs) are precise regions inside the DNA sequence where the replication process begins. These locations are critical for preserving the genome's integrity during cell division and guaranteeing the faithful transfer of genetic data from generation to generation. The advent of experimental techniques has aided in the discovery of ORIs in many species. Experimentation, on the other hand, is often more time-consuming and pricey than computational approaches, and it necessitates specific equipment and knowledge. Recently, ORI sites have been predicted using computational techniques like motif-based searches and artificial intelligence algorithms based on sequence characteristics and chromatin states. RESULTS: In this article, we developed ORI-Explorer, a unique artificial intelligence-based technique that combines multiple feature engineering techniques to train CatBoost Classifier for recognizing ORIs from four distinct eukaryotic species. ORI-Explorer was created by utilizing a unique combination of three traditional feature-encoding techniques and a feature set obtained from a deep-learning neural network model. The ORI-Explorer has significantly outperformed current predictors on the testing dataset. Furthermore, by employing the sophisticated SHapley Additive exPlanation method, we give crucial insights that aid in comprehending model success, highlighting the most relevant features vital for forecasting cell-specific ORIs. ORI-Explorer is also intended to aid community-wide attempts in discovering potential ORIs and developing innovative verifiable biological hypotheses. AVAILABILITY AND IMPLEMENTATION: The used datasets along with the source code are made available through https://github.com/Z-Abbas/ORI-Explorer and https://zenodo.org/record/8358679.


Assuntos
Inteligência Artificial , Origem de Replicação , Replicação do DNA , Cromatina , Sequência de Bases
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