RESUMO
DNA Double-strand breaks (DSBs) are harmful lesions and major sources of genomic instability. Studies have suggested that DSBs induce local transcriptional silencing that consequently promotes genomic stability. Several factors have been proposed to actively participate in this process, including ATM and Polycomb repressive complex 1 (PRC1). Here we found that disrupting PRC1 clustering disrupts DSB-induced gene silencing. Interactome analysis of PHC2, a PRC1 subunit that promotes the formation of the Polycomb body, found several nucleoporins that constitute the Nuclear Pore Complex (NPC). Similar to PHC2, depleting the nucleoporins also disrupted the DSB-induced gene silencing. We found that some of these nucleoporins, such as NUP107 and NUP43, which are members of the Y-complex of NPC, localize to DSB sites. These nucleoporin-enriched DSBs were distant from the nuclear periphery. The presence of nucleoporins and PHC2 at DSB regions were inter-dependent, suggesting that they act cooperatively in the DSB-induced gene silencing. We further found two structural components within NUP107 to be necessary for the transcriptional repression at DSBs: ATM/ATR-mediated phosphorylation at Serine37 residue within the N-terminal disordered tail, and the NUP133-binding surface at the C-terminus. These results provide a new functional interplay among nucleoporins, ATM and the Polycomb proteins in the DSB metabolism, and underscore their emerging roles in genome stability maintenance. *Hongseon Song, Yubin Bae, Sangin Kim, and Dante Deascanis contributed equally to this work.
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Cyclin D1 is the activating subunit of the cell cycle kinases CDK4 and CDK6, and its dysregulation is a well-known oncogenic driver in many human cancers. The biological function of cyclin D1 has been primarily studied by focusing on the phosphorylation of the retinoblastoma (RB) gene product. Here, using an integrative approach combining bioinformatic analyses and biochemical experiments, we show that GTSE1 (G2 and S phases expressed protein 1), a protein positively regulating cell cycle progression, is a previously unknown substrate of cyclin D1-CDK4/6. The phosphorylation of GTSE1 mediated by cyclin D1-CDK4/6 inhibits GTSE1 degradation, leading to high levels of GTSE1 also during the G1 phase of the cell cycle. Functionally, the phosphorylation of GTSE1 promotes cellular proliferation and is associated with poor prognosis within a pan-cancer cohort. Our findings provide insights into cyclin D1's role in cell cycle control and oncogenesis beyond RB phosphorylation.
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Although mismatch repair (MMR) is essential for correcting DNA replication errors, it can also recognize other lesions, such as oxidized bases. In G0 and G1, MMR is kept in check through unknown mechanisms as it is error-prone during these cell cycle phases. We show that in mammalian cells, D-type cyclins are recruited to sites of oxidative DNA damage in a PCNA- and p21-dependent manner. D-type cyclins inhibit the proteasomal degradation of p21, which competes with MMR proteins for binding to PCNA, thereby inhibiting MMR. The ability of D-type cyclins to limit MMR is CDK4- and CDK6-independent and is conserved in G0 and G1. At the G1/S transition, the timely, cullin-RING ubiquitin ligase (CRL)-dependent degradation of D-type cyclins and p21 enables MMR activity to efficiently repair DNA replication errors. Persistent expression of D-type cyclins during S-phase inhibits the binding of MMR proteins to PCNA, increases the mutational burden, and promotes microsatellite instability.
Assuntos
Ciclinas , Reparo de Erro de Pareamento de DNA , Animais , Ciclinas/genética , Antígeno Nuclear de Célula em Proliferação/genética , Antígeno Nuclear de Célula em Proliferação/metabolismo , Inibidor de Quinase Dependente de Ciclina p21/genética , Interfase , Mamíferos/metabolismoRESUMO
The large majority of oxidative DNA lesions occurring in the G1 phase of the cell cycle are repaired by base excision repair (BER) rather than mismatch repair (MMR) to avoid long resections that can lead to genomic instability and cell death. However, the molecular mechanisms dictating pathway choice between MMR and BER have remained unknown. Here, we show that, during G1, D-type cyclins are recruited to sites of oxidative DNA damage in a PCNA- and p21-dependent manner. D-type cyclins shield p21 from its two ubiquitin ligases CRL1SKP2 and CRL4CDT2 in a CDK4/6-independent manner. In turn, p21 competes through its PCNA-interacting protein degron with MMR components for their binding to PCNA. This inhibits MMR while not affecting BER. At the G1/S transition, the CRL4AMBRA1-dependent degradation of D-type cyclins renders p21 susceptible to proteolysis. These timely degradation events allow the proper binding of MMR proteins to PCNA, enabling the repair of DNA replication errors. Persistent expression of cyclin D1 during S-phase increases the mutational burden and promotes microsatellite instability. Thus, the expression of D-type cyclins inhibits MMR in G1, whereas their degradation is necessary for proper MMR function in S.
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Intracellular degradation of proteins and organelles by the autophagy-lysosome system is essential for cellular quality control and energy homeostasis. Besides degradation, endolysosomal organelles can fuse with the plasma membrane and contribute to unconventional secretion. Here, we identify a function for mammalian SKP1 in endolysosomes that is independent of its established role as an essential component of the family of SCF/CRL1 ubiquitin ligases. We found that, under nutrient-poor conditions, SKP1 is phosphorylated on Thr131, allowing its interaction with V1 subunits of the vacuolar ATPase (V-ATPase). This event, in turn, promotes V-ATPase assembly to acidify late endosomes and enhance endolysosomal degradation. Under nutrient-rich conditions, SUMOylation of phosphorylated SKP1 allows its binding to and dephosphorylation by the PPM1B phosphatase. Dephosphorylated SKP1 interacts with SEC22B to promote unconventional secretion of the content of less acidified hybrid endosomal/autophagic compartments. Collectively, our study implicates SKP1 phosphorylation as a switch between autophagy and unconventional secretion in a manner dependent on cellular nutrient status.
Assuntos
Endossomos , ATPases Vacuolares Próton-Translocadoras , Autofagia , Membrana Celular/metabolismo , Endossomos/metabolismo , Lisossomos/metabolismo , ATPases Vacuolares Próton-Translocadoras/química , HumanosRESUMO
Immune-checkpoint blockade has revolutionized cancer treatment, but some cancers, such as acute myeloid leukemia (AML), do not respond or develop resistance. A potential mode of resistance is immune evasion of T cell immunity involving aberrant major histocompatibility complex class I (MHC-I) antigen presentation (AP). To map such mechanisms of resistance, we identified key MHC-I regulators using specific peptide-MHC-I-guided CRISPR-Cas9 screens in AML. The top-ranked negative regulators were surface protein sushi domain containing 6 (SUSD6), transmembrane protein 127 (TMEM127), and the E3 ubiquitin ligase WWP2. SUSD6 is abundantly expressed in AML and multiple solid cancers, and its ablation enhanced MHC-I AP and reduced tumor growth in a CD8+ T cell-dependent manner. Mechanistically, SUSD6 forms a trimolecular complex with TMEM127 and MHC-I, which recruits WWP2 for MHC-I ubiquitination and lysosomal degradation. Together with the SUSD6/TMEM127/WWP2 gene signature, which negatively correlates with cancer survival, our findings define a membrane-associated MHC-I inhibitory axis as a potential therapeutic target for both leukemia and solid cancers.
Assuntos
Antígenos de Histocompatibilidade Classe I , Neoplasias , Evasão Tumoral , Humanos , Apresentação de Antígeno , Linfócitos T CD8-Positivos , Antígenos de Histocompatibilidade Classe I/metabolismo , Antígenos HLA , Neoplasias/imunologia , Ubiquitina-Proteína Ligases/genéticaRESUMO
Cells must avoid licensing of neosynthesized DNA to prevent rereplication. In this issue of Molecular Cell, Ratnayeke et al. (2022)1 reveal how the licensing factor CDT1, prior to its degradation, inhibits DNA elongation by suppressing CMG helicase progression at replication forks.
Assuntos
Proteínas de Ciclo Celular , Replicação do DNA , Proteínas de Ciclo Celular/genética , Proteínas de Ciclo Celular/metabolismo , Proteínas de Ligação a DNA/genética , DNA , DNA Helicases/genéticaRESUMO
DNA has dedicated cellular repair pathways capable of coping with lesions that could arise from both endogenous and/or exogenous sources. DNA repair necessitates collaboration between numerous proteins, responsible for covering a broad range of tasks from recognizing and signaling the presence of a DNA lesion to physically repairing it. During this process, tracks of single-stranded DNA (ssDNA) are often created, which are eventually filled by DNA polymerases. The nature of these ssDNA tracks (in terms of both length and number), along with the polymerase recruited to fill these gaps, are repair pathway-specific. The visualization of these ssDNA tracks can help us understand the complicated dynamics of DNA repair mechanisms. This protocol provides a detailed method for the preparation of G1 synchronized cells to measure ssDNA foci formation upon genotoxic stress. Using an easy-to-utilize immunofluorescence approach, we visualize ssDNA by staining for RPA2, a component of the heterotrimeric replication protein A complex (RPA). RPA2 binds to and stabilizes ssDNA intermediates that arise upon genotoxic stress or replication to control DNA repair and DNA damage checkpoint activation. 5-Ethynyl-2'-deoxyuridine (EdU) staining is used to visualize DNA replication to exclude any S phase cells. This protocol provides an alternative approach to the conventional, non-denaturing 5-bromo-2'-deoxyuridine (BrdU)-based assays and is better suited for the detection of ssDNA foci outside the S phase.
Assuntos
Reparo do DNA , DNA de Cadeia Simples , Ciclo Celular , Divisão Celular , Fase G1RESUMO
The risk of zoonotic coronavirus spillover into the human population, as highlighted by the SARS-CoV-2 pandemic, demands the development of pan-coronavirus antivirals. The efficacy of existing antiviral ribonucleoside/ribonucleotide analogs, such as remdesivir, is decreased by the viral proofreading exonuclease NSP14-NSP10 complex. Here, using a novel assay and in silico modeling and screening, we identified NSP14-NSP10 inhibitors that increase remdesivir's potency. A model compound, sofalcone, both inhibits the exonuclease activity of SARS-CoV-2, SARS-CoV, and MERS-CoV in vitro, and synergistically enhances the antiviral effect of remdesivir, suppressing the replication of SARS-CoV-2 and the related human coronavirus OC43. The validation of top hits from our primary screenings using cellular systems provides proof-of-concept for the NSP14 complex as a therapeutic target.
Assuntos
Monofosfato de Adenosina/análogos & derivados , Alanina/análogos & derivados , Exorribonucleases/metabolismo , SARS-CoV-2/efeitos dos fármacos , Proteínas não Estruturais Virais/metabolismo , Proteínas Virais Reguladoras e Acessórias/metabolismo , Células A549 , Monofosfato de Adenosina/farmacologia , Alanina/farmacologia , Antivirais/farmacologia , Humanos , SARS-CoV-2/enzimologia , Replicação Viral/efeitos dos fármacosRESUMO
DNA damage repair maintains the genetic integrity of cells in a highly reactive environment. Cells may accumulate various types of DNA damage due to both endogenous and exogenous sources such as metabolic activities or UV radiation. Without DNA repair, the cell's genetic code becomes compromised, undermining the structures and functions of proteins and potentially causing disease. Understanding the spatiotemporal dynamics of the different DNA repair pathways in various cell cycle phases is crucial in the field of DNA damage repair. Current fluorescent microscopy techniques provide great tools to measure the recruitment kinetics of different repair proteins after DNA damage induction. DNA synthesis during the S phase of the cell cycle is a peculiar point in cell fate regarding DNA repair. It provides a unique window to screen the entire genome for mistakes. At the same time, DNA synthesis errors also pose a threat to DNA integrity that is not encountered in non-dividing cells. Therefore, DNA repair processes differ significantly in S phase as compared to other phases of the cell cycle, and those differences are poorly understood. The following protocol describes the preparation of cell lines and the measurement of dynamics of DNA repair proteins in S phase at locally induced DNA damage sites, using a laser-scanning confocal microscope equipped with a 405 nm laser line. Tagged PCNA (with mPlum) is used as a cell cycle marker combined with an AcGFP-labeled repair protein of interest (i.e., EXO1b) to measure the DNA damage recruitment in S phase.
Assuntos
Dano ao DNA/genética , DNA/genética , Terapia a Laser/métodos , Fase S/genética , Terapia Ultravioleta/métodos , HumanosRESUMO
In order to understand the transmission and virulence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), it is necessary to understand the functions of each of the gene products encoded in the viral genome. One feature of the SARS-CoV-2 genome that is not present in related, common coronaviruses is ORF10, a putative 38-amino acid protein-coding gene. Proteomic studies found that ORF10 binds to an E3 ubiquitin ligase containing Cullin-2, Rbx1, Elongin B, Elongin C, and ZYG11B (CRL2ZYG11B). Since CRL2ZYG11B mediates protein degradation, one possible role for ORF10 is to "hijack" CRL2ZYG11B in order to target cellular, antiviral proteins for ubiquitylation and subsequent proteasomal degradation. Here, we investigated whether ORF10 hijacks CRL2ZYG11B or functions in other ways, for example, as an inhibitor or substrate of CRL2ZYG11B While we confirm the ORF10-ZYG11B interaction and show that the N terminus of ORF10 is critical for it, we find no evidence that ORF10 is functioning to inhibit or hijack CRL2ZYG11B Furthermore, ZYG11B and its paralog ZER1 are dispensable for SARS-CoV-2 infection in cultured cells. We conclude that the interaction between ORF10 and CRL2ZYG11B is not relevant for SARS-CoV-2 infection in vitro.
Assuntos
COVID-19/metabolismo , Proteínas de Ciclo Celular/metabolismo , Proteínas Culina/metabolismo , Complexos Multiproteicos/metabolismo , Fases de Leitura Aberta , SARS-CoV-2/metabolismo , Proteínas Virais/metabolismo , COVID-19/genética , Proteínas de Ciclo Celular/genética , Proteínas Culina/genética , Células HEK293 , Humanos , Complexos Multiproteicos/genética , SARS-CoV-2/genética , Proteínas Virais/genéticaRESUMO
Mammalian development, adult tissue homeostasis and the avoidance of severe diseases including cancer require a properly orchestrated cell cycle, as well as error-free genome maintenance. The key cell-fate decision to replicate the genome is controlled by two major signalling pathways that act in parallel-the MYC pathway and the cyclin D-cyclin-dependent kinase (CDK)-retinoblastoma protein (RB) pathway1,2. Both MYC and the cyclin D-CDK-RB axis are commonly deregulated in cancer, and this is associated with increased genomic instability. The autophagic tumour-suppressor protein AMBRA1 has been linked to the control of cell proliferation, but the underlying molecular mechanisms remain poorly understood. Here we show that AMBRA1 is an upstream master regulator of the transition from G1 to S phase and thereby prevents replication stress. Using a combination of cell and molecular approaches and in vivo models, we reveal that AMBRA1 regulates the abundance of D-type cyclins by mediating their degradation. Furthermore, by controlling the transition from G1 to S phase, AMBRA1 helps to maintain genomic integrity during DNA replication, which counteracts developmental abnormalities and tumour growth. Finally, we identify the CHK1 kinase as a potential therapeutic target in AMBRA1-deficient tumours. These results advance our understanding of the control of replication-phase entry and genomic integrity, and identify the AMBRA1-cyclin D pathway as a crucial cell-cycle-regulatory mechanism that is deeply interconnected with genomic stability in embryonic development and tumorigenesis.
Assuntos
Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Ciclina D/metabolismo , Instabilidade Genômica , Fase S , Animais , Linhagem Celular , Proliferação de Células , Quinase 1 do Ponto de Checagem/antagonistas & inibidores , Quinases Ciclina-Dependentes/metabolismo , Replicação do DNA , Regulação da Expressão Gênica no Desenvolvimento , Genes Supressores de Tumor , Humanos , Camundongos , Camundongos Knockout , Mutações Sintéticas LetaisRESUMO
D-type cyclins are central regulators of the cell division cycle and are among the most frequently deregulated therapeutic targets in human cancer1, but the mechanisms that regulate their turnover are still being debated2,3. Here, by combining biochemical and genetics studies in somatic cells, we identify CRL4AMBRA1 (also known as CRL4DCAF3) as the ubiquitin ligase that targets all three D-type cyclins for degradation. During development, loss of Ambra1 induces the accumulation of D-type cyclins and retinoblastoma (RB) hyperphosphorylation and hyperproliferation, and results in defects of the nervous system that are reduced by treating pregnant mice with the FDA-approved CDK4 and CDK6 (CDK4/6) inhibitor abemaciclib. Moreover, AMBRA1 acts as a tumour suppressor in mouse models and low AMBRA1 mRNA levels are predictive of poor survival in cancer patients. Cancer hotspot mutations in D-type cyclins abrogate their binding to AMBRA1 and induce their stabilization. Finally, a whole-genome, CRISPR-Cas9 screen identified AMBRA1 as a regulator of the response to CDK4/6 inhibition. Loss of AMBRA1 reduces sensitivity to CDK4/6 inhibitors by promoting the formation of complexes of D-type cyclins with CDK2. Collectively, our results reveal the molecular mechanism that controls the stability of D-type cyclins during cell-cycle progression, in development and in human cancer, and implicate AMBRA1 as a critical regulator of the RB pathway.
Assuntos
Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Divisão Celular , Ciclina D1/metabolismo , Proteínas Adaptadoras de Transdução de Sinal/genética , Animais , Sistemas CRISPR-Cas , Ciclina D2/metabolismo , Ciclina D3/metabolismo , Quinase 2 Dependente de Ciclina/metabolismo , Quinase 4 Dependente de Ciclina/antagonistas & inibidores , Quinase 6 Dependente de Ciclina/antagonistas & inibidores , Feminino , Técnicas de Inativação de Genes , Genes Supressores de Tumor , Células HCT116 , Células HEK293 , Humanos , Masculino , Camundongos , Neoplasias/genética , Ubiquitina/metabolismoRESUMO
Numerous anti-cancer drugs perturb thymidylate biosynthesis and lead to genomic uracil incorporation contributing to their antiproliferative effect. Still, it is not yet characterized if uracil incorporations have any positional preference. Here, we aimed to uncover genome-wide alterations in uracil pattern upon drug treatments in human cancer cell line models derived from HCT116. We developed a straightforward U-DNA sequencing method (U-DNA-Seq) that was combined with in situ super-resolution imaging. Using a novel robust analysis pipeline, we found broad regions with elevated probability of uracil occurrence both in treated and non-treated cells. Correlation with chromatin markers and other genomic features shows that non-treated cells possess uracil in the late replicating constitutive heterochromatic regions, while drug treatment induced a shift of incorporated uracil towards segments that are normally more active/functional. Data were corroborated by colocalization studies via dSTORM microscopy. This approach can be applied to study the dynamic spatio-temporal nature of genomic uracil.
Assuntos
Antineoplásicos/farmacologia , DNA , Genoma , Uracila , DNA/análise , DNA/biossíntese , DNA/química , DNA/genética , Genoma/efeitos dos fármacos , Genoma/genética , Genômica , Células HCT116 , Humanos , Microscopia , Análise de Sequência de DNA , Uracila/análise , Uracila/biossíntese , Uracila/químicaRESUMO
BACKGROUND: The SMC5/6 complex, cohesin and condensin are the three mammalian members of the structural maintenance of chromosomes (SMC) family, large ring-like protein complexes that are essential for genome maintenance. The SMC5/6 complex is the least characterized complex in mammals; however, it is known to be involved in homologous recombination repair (HRR) and chromosome segregation. RESULTS: In this study, a yeast two-hybrid screen was used to help elucidate novel interactions of the kleisin subunit of the SMC5/6 complex, NSMCE4A. This approach discovered an interaction between NSMCE4A and GPS1, a COP9 signalosome (CSN) component, and this interaction was further confirmed by co-immunoprecipitation. Additionally, GPS1 and components of SMC5/6 complex colocalize during interphase and mitosis. CSN is a cullin deNEDDylase and is an important factor for HRR. Depletion of GPS1, which has been shown to negatively impact DNA end resection during HRR, caused an increase in SMC5/6 levels at sites of laser-induced DNA damage. Furthermore, inhibition of the dennedylation function of CSN increased SMC5/6 levels at sites of laser-induced DNA damage. CONCLUSION: Taken together, these data demonstrate for the first time that the SMC5/6 and CSN complexes interact and provides evidence that the CSN complex influences SMC5/6 functions during cell cycle progression and response to DNA damage.
Assuntos
Complexo do Signalossomo COP9/metabolismo , Proteínas de Ciclo Celular/metabolismo , Núcleo Celular/metabolismo , Proteínas Cromossômicas não Histona/metabolismo , Complexo do Signalossomo COP9/antagonistas & inibidores , Complexo do Signalossomo COP9/genética , Proteínas de Ciclo Celular/genética , Linhagem Celular Tumoral , Proteínas Cromossômicas não Histona/genética , Citoplasma/metabolismo , Dano ao DNA/genética , Dano ao DNA/efeitos da radiação , Reparo do DNA , Humanos , Interfase/genética , Mitose/genética , Processamento de Proteína Pós-Traducional , RNA Interferente Pequeno , Técnicas do Sistema de Duplo-HíbridoRESUMO
Diverse linkage in polyubiquitin chain structure gives cells an unparalleled complexity to virtually modulate all aspects of cell biology. Substrates can be covalently modified by ubiquitin chains of different topology. Proper DNA damage response takes advantage of this regulatory system and heavily relies on ubiquitin-based signaling. Moreover, increasing evidence suggests that chain specificity dictates DNA repair outcome. In this issue of Genes & Development, Wu and colleagues (pp. 1702-1717) show that Cezanne and Cezanne2, two paralogous deubiquitinating enzymes that are recruited to sites of DNA damage, ensure proper local polyubiquitin chain composition for downstream DNA repair protein assembly. Their study offers a key insight into the mechanism of crosstalk between linkage-specific ubiquitylation at DNA damage sites, while simultaneously raising important questions for future research.
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Poliubiquitina , Ubiquitina , Dano ao DNA , Reparo do DNA , Ligação Proteica , UbiquitinaçãoRESUMO
Epithelial to mesenchymal transition (EMT) is a multipurpose process involved in wound healing, development, and certain pathological processes, such as metastasis formation. The Tks4 scaffold protein has been implicated in cancer progression; however, its role in oncogenesis is not well defined. In this study, the function of Tks4 was investigated in HCT116 colon cancer cells by knocking the protein out using the CRISPR/Cas9 system. Surprisingly, the absence of Tks4 induced significant changes in cell morphology, motility, adhesion and expression, and localization of E-cadherin, which are all considered as hallmarks of EMT. In agreement with these findings, the marked appearance of fibronectin, a marker of the mesenchymal phenotype, was also observed in Tks4-KO cells. Analysis of the expression of well-known EMT transcription factors revealed that Snail2 was strongly overexpressed in cells lacking Tks4. Tks4-KO cells showed increased motility and decreased cell-cell attachment. Collagen matrix invasion assays demonstrated the abundance of invasive solitary cells. Finally, the reintroduction of Tks4 protein in the Tks4-KO cells restored the expression levels of relevant key transcription factors, suggesting that the Tks4 scaffold protein has a specific and novel role in EMT regulation and cancer progression.
Assuntos
Proteínas Adaptadoras de Transdução de Sinal/fisiologia , Neoplasias do Colo/genética , Transição Epitelial-Mesenquimal/genética , Proteínas Adaptadoras de Transdução de Sinal/genética , Movimento Celular/genética , Transformação Celular Neoplásica/genética , Neoplasias do Colo/patologia , Regulação Neoplásica da Expressão Gênica , Técnicas de Inativação de Genes , Células HCT116 , Humanos , Invasividade Neoplásica , Transdução de Sinais/genéticaRESUMO
Sanitization of nucleotide pools is essential for genome maintenance. Deoxyuridine 5'-triphosphate nucleotidohydrolase (dUTPase) is a key enzyme in this pathway since it catalyzes the cleavage of 2'-deoxyuridine 5'-triphosphate (dUTP) into 2'-deoxyuridine 5'-monophosphate (dUMP) and inorganic pyrophosphate. Through its action dUTPase efficiently prevents uracil misincorporation into DNA and at the same time provides dUMP, the substrate for de novo thymidylate biosynthesis. Despite its physiological significance, knock-out models of dUTPase have not yet been investigated in mammals, but only in unicellular organisms, such as bacteria and yeast. Here we generate CRISPR/Cas9-mediated dUTPase knock-out in mice. We find that heterozygous dut +/- animals are viable while having decreased dUTPase levels. Importantly, we show that dUTPase is essential for embryonic development since early dut -/- embryos reach the blastocyst stage, however, they die shortly after implantation. Analysis of pre-implantation embryos indicates perturbed growth of both inner cell mass (ICM) and trophectoderm (TE). We conclude that dUTPase is indispensable for post-implantation development in mice.
Assuntos
Desenvolvimento Embrionário/genética , Deleção de Genes , Pirofosfatases/genética , Animais , Blastocisto/metabolismo , Blastocisto/patologia , Sistemas CRISPR-Cas , Células Cultivadas , Heterozigoto , Homozigoto , Camundongos , Camundongos Knockout , Pirofosfatases/metabolismoRESUMO
The mammalian FBXL10-RNF68-RNF2 ubiquitin ligase complex (FRRUC) mono-ubiquitylates H2A at Lys119 to repress transcription in unstressed cells. We found that the FRRUC is rapidly and transiently recruited to sites of DNA damage in a PARP1- and TIMELESS-dependent manner to promote mono-ubiquitylation of H2A at Lys119, a local decrease of H2A levels, and an increase of H2A.Z incorporation. Both the FRRUC and H2A.Z promote transcriptional repression, double strand break signaling, and homologous recombination repair (HRR). All these events require both the presence and activity of the FRRUC. Moreover, the FRRUC and its activity are required for the proper recruitment of BMI1-RNF2 and MEL18-RNF2, two other ubiquitin ligases that mono-ubiquitylate Lys119 in H2A upon genotoxic stress. Notably, whereas H2A.Z is not required for H2A mono-ubiquitylation, impairment of the latter results in the inhibition of H2A.Z incorporation. We propose that the recruitment of the FRRUC represents an early and critical regulatory step in HRR.
Assuntos
Dano ao DNA , Proteínas F-Box/metabolismo , Histonas/metabolismo , Histona Desmetilases com o Domínio Jumonji/metabolismo , Poli(ADP-Ribose) Polimerase-1/metabolismo , Complexo Repressor Polycomb 1/metabolismo , Linhagem Celular , Reparo do DNA/genética , Proteínas F-Box/química , Recombinação Homóloga/genética , Humanos , Histona Desmetilases com o Domínio Jumonji/química , Cinética , Lisina/metabolismo , Domínios Proteicos , Multimerização Proteica , Subunidades Proteicas/metabolismo , RNA Interferente Pequeno/metabolismo , Transcrição Gênica , UbiquitinaçãoRESUMO
Transmembrane proteins play crucial role in signaling, ion transport, nutrient uptake, as well as in maintaining the dynamic equilibrium between the internal and external environment of cells. Despite their important biological functions and abundance, less than 2% of all determined structures are transmembrane proteins. Given the persisting technical difficulties associated with high resolution structure determination of transmembrane proteins, additional methods, including computational and experimental techniques remain vital in promoting our understanding of their topologies, 3D structures, functions and interactions. Here we report a method for the high-throughput determination of extracellular segments of transmembrane proteins based on the identification of surface labeled and biotin captured peptide fragments by LC/MS/MS. We show that reliable identification of extracellular protein segments increases the accuracy and reliability of existing topology prediction algorithms. Using the experimental topology data as constraints, our improved prediction tool provides accurate and reliable topology models for hundreds of human transmembrane proteins.