RESUMEN
Lung cancer in East Asia is characterized by a high percentage of never-smokers, early onset and predominant EGFR mutations. To illuminate the molecular phenotype of this demographically distinct disease, we performed a deep comprehensive proteogenomic study on a prospectively collected cohort in Taiwan, representing early stage, predominantly female, non-smoking lung adenocarcinoma. Integrated genomic, proteomic, and phosphoproteomic analysis delineated the demographically distinct molecular attributes and hallmarks of tumor progression. Mutational signature analysis revealed age- and gender-related mutagenesis mechanisms, characterized by high prevalence of APOBEC mutational signature in younger females and over-representation of environmental carcinogen-like mutational signatures in older females. A proteomics-informed classification distinguished the clinical characteristics of early stage patients with EGFR mutations. Furthermore, integrated protein network analysis revealed the cellular remodeling underpinning clinical trajectories and nominated candidate biomarkers for patient stratification and therapeutic intervention. This multi-omic molecular architecture may help develop strategies for management of early stage never-smoker lung adenocarcinoma.
Asunto(s)
Progresión de la Enfermedad , Neoplasias Pulmonares/genética , Neoplasias Pulmonares/patología , Proteogenómica , Fumar/genética , Adenocarcinoma del Pulmón/genética , Adenocarcinoma del Pulmón/patología , Biomarcadores de Tumor/genética , Biomarcadores de Tumor/metabolismo , Carcinógenos/toxicidad , Estudios de Cohortes , Citosina Desaminasa/metabolismo , Asia Oriental , Regulación Neoplásica de la Expresión Génica , Redes Reguladoras de Genes , Genoma Humano , Humanos , Metaloproteinasas de la Matriz/metabolismo , Mutación/genética , Análisis de Componente PrincipalRESUMEN
Multiple signatures of somatic mutations have been identified in cancer genomes. Exome sequences of 1,001 human cancer cell lines and 577 xenografts revealed most common mutational signatures, indicating past activity of the underlying processes, usually in appropriate cancer types. To investigate ongoing patterns of mutational-signature generation, cell lines were cultured for extended periods and subsequently DNA sequenced. Signatures of discontinued exposures, including tobacco smoke and ultraviolet light, were not generated in vitro. Signatures of normal and defective DNA repair and replication continued to be generated at roughly stable mutation rates. Signatures of APOBEC cytidine deaminase DNA-editing exhibited substantial fluctuations in mutation rate over time with episodic bursts of mutations. The initiating factors for the bursts are unclear, although retrotransposon mobilization may contribute. The examined cell lines constitute a resource of live experimental models of mutational processes, which potentially retain patterns of activity and regulation operative in primary human cancers.
Asunto(s)
Desaminasas APOBEC/genética , Neoplasias/genética , Desaminasas APOBEC/metabolismo , Línea Celular , Línea Celular Tumoral , ADN/metabolismo , Análisis Mutacional de ADN/métodos , Bases de Datos Genéticas , Exoma , Genoma Humano/genética , Xenoinjertos , Humanos , Mutagénesis , Mutación/genética , Tasa de Mutación , Retroelementos , Secuenciación del Exoma/métodosRESUMEN
We report a comprehensive analysis of 412 muscle-invasive bladder cancers characterized by multiple TCGA analytical platforms. Fifty-eight genes were significantly mutated, and the overall mutational load was associated with APOBEC-signature mutagenesis. Clustering by mutation signature identified a high-mutation subset with 75% 5-year survival. mRNA expression clustering refined prior clustering analyses and identified a poor-survival "neuronal" subtype in which the majority of tumors lacked small cell or neuroendocrine histology. Clustering by mRNA, long non-coding RNA (lncRNA), and miRNA expression converged to identify subsets with differential epithelial-mesenchymal transition status, carcinoma in situ scores, histologic features, and survival. Our analyses identified 5 expression subtypes that may stratify response to different treatments.
Asunto(s)
Neoplasias de la Vejiga Urinaria/genética , Neoplasias de la Vejiga Urinaria/patología , Anciano , Análisis por Conglomerados , Metilación de ADN , Humanos , MicroARNs/genética , Persona de Mediana Edad , Músculo Liso/patología , ARN Largo no Codificante/genética , Análisis de Supervivencia , Vejiga Urinaria/patología , Neoplasias de la Vejiga Urinaria/epidemiología , Neoplasias de la Vejiga Urinaria/terapiaRESUMEN
Abasic sites are DNA lesions repaired by base excision repair. Cleavage of unrepaired abasic sites in single-stranded DNA (ssDNA) can lead to chromosomal breakage during DNA replication. How rupture of abasic DNA is prevented remains poorly understood. Here, using cryoelectron microscopy (cryo-EM), Xenopus laevis egg extracts, and human cells, we show that RAD51 nucleofilaments specifically recognize and protect abasic sites, which increase RAD51 association rate to DNA. In the absence of BRCA2 or RAD51, abasic sites accumulate as a result of DNA base methylation, oxidation, and deamination, inducing abasic ssDNA gaps that make replicating DNA fibers sensitive to APE1. RAD51 assembled on abasic DNA prevents abasic site cleavage by the MRE11-RAD50 complex, suppressing replication fork breakage triggered by an excess of abasic sites or POLθ polymerase inhibition. Our study highlights the critical role of BRCA2 and RAD51 in safeguarding against unrepaired abasic sites in DNA templates stemming from base alterations, ensuring genomic stability.
Asunto(s)
Proteína BRCA2 , Daño del ADN , Reparación del ADN , Replicación del ADN , ADN de Cadena Simple , Recombinasa Rad51 , Xenopus laevis , Humanos , Recombinasa Rad51/metabolismo , Recombinasa Rad51/genética , Proteína BRCA2/genética , Proteína BRCA2/metabolismo , Animales , ADN de Cadena Simple/metabolismo , ADN de Cadena Simple/genética , Microscopía por Crioelectrón , ADN Polimerasa theta , Metilación de ADN , ADN Polimerasa Dirigida por ADN/metabolismo , ADN Polimerasa Dirigida por ADN/genética , Proteína Homóloga de MRE11/metabolismo , Proteína Homóloga de MRE11/genética , Proteínas de Unión al ADN/metabolismo , Proteínas de Unión al ADN/genéticaRESUMEN
The initiation, progression, and relapse of cancers often result from mutations occurring within somatic cells. Consequently, processes that elevate mutation rates accelerate carcinogenesis and hinder the development of long-lasting therapeutics. Recent sequencing of human cancer genomes has identified patterns of mutations, termed mutation signatures, many of which correspond to specific environmentally induced and endogenous mutation processes. Some of the most frequently observed mutation signatures are caused by dysregulated activity of APOBECs, which deaminate cytidines in single-stranded DNA at specific sequence motifs causing C-to-T and C-to-G substitutions. In humans, APOBEC-generated genetic heterogeneity in tumor cells contributes to carcinogenesis, metastasis, and resistance to therapeutics. Here, we review the current understanding of APOBECs' role in cancer mutagenesis and impact on disease and the biological processes that influence APOBEC mutagenic capacity.
Asunto(s)
Neoplasias , Humanos , Mutagénesis/genética , Neoplasias/genética , Núcleo Celular , Mutación , Carcinogénesis/genéticaRESUMEN
Telomere crisis occurs during tumorigenesis when depletion of the telomere reserve leads to frequent telomere fusions. The resulting dicentric chromosomes have been proposed to drive genome instability. Here, we examine the fate of dicentric human chromosomes in telomere crisis. We observed that dicentric chromosomes invariably persisted through mitosis and developed into 50-200 µm chromatin bridges connecting the daughter cells. Before their resolution at 3-20 hr after anaphase, the chromatin bridges induced nuclear envelope rupture in interphase, accumulated the cytoplasmic 3' nuclease TREX1, and developed RPA-coated single stranded (ss) DNA. CRISPR knockouts showed that TREX1 contributed to the generation of the ssDNA and the resolution of the chromatin bridges. Post-crisis clones showed chromothripsis and kataegis, presumably resulting from DNA repair and APOBEC editing of the fragmented chromatin bridge DNA. We propose that chromothripsis in human cancer may arise through TREX1-mediated fragmentation of dicentric chromosomes formed in telomere crisis.
Asunto(s)
Inestabilidad Cromosómica , Cromosomas Humanos , Inestabilidad Genómica , Neoplasias/genética , Telómero , Aberraciones Cromosómicas , Citocinesis , ADN de Cadena Simple/metabolismo , Exodesoxirribonucleasas/metabolismo , Humanos , Mitosis , Membrana Nuclear/metabolismo , Fosfoproteínas/metabolismoRESUMEN
Activation-induced cytidine deaminase (AID) initiates somatic hypermutation (SHM) by introducing base substitutions into antibody genes, a process enabling antibody affinity maturation in immune response. How a mutator is tamed to precisely and safely generate programmed DNA lesions in a physiological process remains unsettled, as its dysregulation drives lymphomagenesis. Recent research has revealed several hidden features of AID-initiated mutagenesis: preferential activity on flexible DNA substrates, restrained activity within chromatin loop domains, unique DNA repair factors to differentially decode AID-caused lesions, and diverse consequences of aberrant deamination. Here, we depict the multifaceted regulation of AID activity with a focus on emerging concepts/factors and discuss their implications for the design of base editors (BEs) that install somatic mutations to correct deleterious genomic variants.
Asunto(s)
Citidina Desaminasa , Hipermutación Somática de Inmunoglobulina , Citidina Desaminasa/metabolismo , Citidina Desaminasa/genética , Humanos , Animales , Mutación , Reparación del ADNRESUMEN
One of the two chromosomal breakage events in recurring translocations in B cell neoplasms is often due to the recombination-activating gene complex (RAG complex) releasing DNA ends before end joining. The other break occurs in a fragile zone of 20-600 bp in a non-antigen receptor gene locus, with a more complex and intriguing set of mechanistic factors underlying such narrow fragile zones. These factors include activation-induced deaminase (AID), which acts only at regions of single-stranded DNA (ssDNA). Recent work leads to a model involving the tethering of AID to the nascent RNA as it emerges from the RNA polymerase. This mechanism may have relevance in class switch recombination (CSR) and somatic hypermutation (SHM), as well as broader relevance for other DNA enzymes.
Asunto(s)
ARN , Translocación Genética , Humanos , ARN/metabolismo , ARN/genética , Citidina Desaminasa/metabolismo , Citidina Desaminasa/genética , Sitios Frágiles del CromosomaRESUMEN
Long interspersed element-1 (LINE-1 or L1) retrotransposition poses a threat to genome integrity, and cells have evolved mechanisms to restrict retrotransposition. However, how cellular proteins facilitate L1 retrotransposition requires elucidation. Here, we demonstrate that single-strand DNA breaks induced by the L1 endonuclease trigger the recruitment of poly(ADP-ribose) polymerase 2 (PARP2) to L1 integration sites and that PARP2 activation leads to the subsequent recruitment of the replication protein A (RPA) complex to facilitate retrotransposition. We further demonstrate that RPA directly binds activated PARP2 through poly(ADP-ribosyl)ation and can protect single-strand L1 integration intermediates from APOBEC3-mediated cytidine deamination in vitro. Paradoxically, we provide evidence that RPA can guide APOBEC3A, and perhaps other APOBEC3 proteins, to sites of L1 integration. Thus, the interplay of L1-encoded and evolutionarily conserved cellular proteins is required for efficient retrotransposition; however, these interactions also may be exploited to restrict L1 retrotransposition in the human genome.
Asunto(s)
Elementos de Nucleótido Esparcido Largo , Poli(ADP-Ribosa) Polimerasas/metabolismo , Proteína de Replicación A/metabolismo , Desaminasas APOBEC , Animales , Células CHO , Cricetulus , Citidina Desaminasa/genética , Citidina Desaminasa/metabolismo , Células HEK293 , Células HeLa , Humanos , Poli(ADP-Ribosa) Polimerasas/genética , Unión Proteica , Proteína de Replicación A/genéticaRESUMEN
Human retroviruses are derived from simian ones through cross-species transmission. These retroviruses are associated with little pathogenicity in their natural hosts, but in humans, HIV causes AIDS, and human T-cell leukemia virus type 1 (HTLV-1) induces adult T-cell leukemia-lymphoma (ATL). We analyzed the proviral sequences of HTLV-1, HTLV-2, and simian T-cell leukemia virus type 1 (STLV-1) from Japanese macaques (Macaca fuscata) and found that APOBEC3G (A3G) frequently generates G-to-A mutations in the HTLV-1 provirus, whereas such mutations are rare in the HTLV-2 and STLV-1 proviruses. Therefore, we investigated the mechanism of how HTLV-2 is resistant to human A3G (hA3G). HTLV-1, HTLV-2, and STLV-1 encode the so-called antisense proteins, HTLV-1 bZIP factor (HBZ), Antisense protein of HTLV-2 (APH-2), and STLV-1 bZIP factor (SBZ), respectively. APH-2 efficiently inhibits the deaminase activity of both hA3G and simian A3G (sA3G). HBZ and SBZ strongly suppress sA3G activity but only weakly inhibit hA3G, suggesting that HTLV-1 is incompletely adapted to humans. Unexpectedly, hA3G augments the activation of the transforming growth factor (TGF)-ß/Smad pathway by HBZ, and this activation is associated with ATL cell proliferation by up-regulating BATF3/IRF4 and MYC. In contrast, the combination of APH-2 and hA3G, or the combination of SBZ and sA3G, does not enhance the TGF-ß/Smad pathway. Thus, HTLV-1 is vulnerable to hA3G but utilizes it to promote the proliferation of infected cells via the activation of the TGF-ß/Smad pathway. Antisense factors in each virus, differently adapted to control host cellular functions through A3G, seem to dictate the pathogenesis.
Asunto(s)
Virus Linfotrópico T Tipo 1 Humano , Leucemia-Linfoma de Células T del Adulto , Humanos , Línea Celular , Virulencia , Virus Linfotrópico T Tipo 1 Humano/metabolismo , Leucemia-Linfoma de Células T del Adulto/genética , Provirus/genética , Factor de Crecimiento Transformador beta/metabolismo , Factores de Transcripción con Cremalleras de Leucina de Carácter Básico/genética , Factores de Transcripción con Cremalleras de Leucina de Carácter Básico/metabolismo , Desaminasa APOBEC-3G/genéticaRESUMEN
The apolipoprotein B messenger RNA editing enzyme, catalytic polypeptide (APOBEC) family is composed of nucleic acid editors with roles ranging from antibody diversification to RNA editing. APOBEC2, a member of this family with an evolutionarily conserved nucleic acid-binding cytidine deaminase domain, has neither an established substrate nor function. Using a cellular model of muscle differentiation where APOBEC2 is inducibly expressed, we confirmed that APOBEC2 does not have the attributed molecular functions of the APOBEC family, such as RNA editing, DNA demethylation, and DNA mutation. Instead, we found that during muscle differentiation APOBEC2 occupied a specific motif within promoter regions; its removal from those regions resulted in transcriptional changes. Mechanistically, these changes reflect the direct interaction of APOBEC2 with histone deacetylase (HDAC) transcriptional corepressor complexes. We also found that APOBEC2 could bind DNA directly, in a sequence-specific fashion, suggesting that it functions as a recruiter of HDAC to specific genes whose promoters it occupies. These genes are normally suppressed during muscle cell differentiation, and their suppression may contribute to the safeguarding of muscle cell fate. Altogether, our results reveal a unique role for APOBEC2 within the APOBEC family.
Asunto(s)
Cromatina , Proteínas Musculares , Desaminasas APOBEC/genética , Desaminasas APOBEC-1/genética , Diferenciación Celular/genética , Cromatina/genética , Citidina Desaminasa/metabolismo , ADN , Fibras Musculares Esqueléticas/metabolismo , Proteínas Musculares/metabolismo , Mioblastos/metabolismo , ARN Mensajero/genética , Animales , RatonesRESUMEN
Human APOBEC3H and homologous single-stranded DNA cytosine deaminases are unique to mammals. These DNA-editing enzymes function in innate immunity by restricting the replication of viruses and transposons. APOBEC3H also contributes to cancer mutagenesis. Here, we address the fundamental nature of RNA in regulating human APOBEC3H activities. APOBEC3H co-purifies with RNA as an inactive protein, and RNase A treatment enables strong DNA deaminase activity. RNA-binding-defective mutants demonstrate clear separation of function by becoming DNA hypermutators. Biochemical and crystallographic data demonstrate a mechanism in which double-stranded RNA mediates enzyme dimerization. Additionally, APOBEC3H separation-of-function mutants show that RNA binding is required for cytoplasmic localization, packaging into HIV-1 particles, and antiviral activity. Overall, these results support a model in which structured RNA negatively regulates the potentially harmful DNA deamination activity of APOBEC3H while, at the same time, positively regulating its antiviral activity.
Asunto(s)
Aminohidrolasas/metabolismo , Dimerización , VIH-1/crecimiento & desarrollo , Ensamble de Virus/genética , Aminohidrolasas/genética , Línea Celular Tumoral , Cristalografía por Rayos X , Citosina Desaminasa/metabolismo , Células HEK293 , Células HeLa , Humanos , Estructura Secundaria de Proteína , ARN/genética , ARN/metabolismo , Proteínas de Unión al ARN/genética , Ribonucleasa Pancreática/metabolismoRESUMEN
Human APOBEC3 enzymes are a family of single-stranded (ss)DNA and RNA cytidine deaminases that act as part of the intrinsic immunity against viruses and retroelements. These enzymes deaminate cytosine to form uracil which can functionally inactivate or cause degradation of viral or retroelement genomes. In addition, APOBEC3s have deamination-independent antiviral activity through protein and nucleic acid interactions. If expression levels are misregulated, some APOBEC3 enzymes can access the human genome leading to deamination and mutagenesis, contributing to cancer initiation and evolution. While APOBEC3 enzymes are known to interact with large ribonucleoprotein complexes, the function and RNA dependence are not entirely understood. To further understand their cellular roles, we determined by affinity purification mass spectrometry (AP-MS) the protein interaction network for the human APOBEC3 enzymes and mapped a diverse set of protein-protein and protein-RNA mediated interactions. Our analysis identified novel RNA-mediated interactions between APOBEC3C, APOBEC3H Haplotype I and II, and APOBEC3G with spliceosome proteins, and APOBEC3G and APOBEC3H Haplotype I with proteins involved in tRNA methylation and ncRNA export from the nucleus. In addition, we identified RNA-independent protein-protein interactions with APOBEC3B, APOBEC3D, and APOBEC3F and the prefoldin family of protein-folding chaperones. Interaction between prefoldin 5 (PFD5) and APOBEC3B disrupted the ability of PFD5 to induce degradation of the oncogene cMyc, implicating the APOBEC3B protein interaction network in cancer. Altogether, the results uncover novel functions and interactions of the APOBEC3 family and suggest they may have fundamental roles in cellular RNA biology, their protein-protein interactions are not redundant, and there are protein-protein interactions with tumor suppressors, suggesting a role in cancer biology. Data are available via ProteomeXchange with the identifier PXD044275.
Asunto(s)
Citidina Desaminasa , Mapas de Interacción de Proteínas , Humanos , Citidina Desaminasa/metabolismo , Citidina Desaminasa/genética , Desaminación , Desaminasas APOBEC/metabolismo , Aminohidrolasas/metabolismo , Aminohidrolasas/genética , Células HEK293 , Citosina Desaminasa/metabolismo , Desaminasa APOBEC-3G/metabolismo , Desaminasa APOBEC-3G/genética , Empalmosomas/metabolismo , Unión Proteica , Espectrometría de Masas , ARN/metabolismo , Antígenos de Histocompatibilidad Menor/metabolismo , Antígenos de Histocompatibilidad Menor/genéticaRESUMEN
Over the past decade, the connection between APOBEC3 cytosine deaminases and cancer mutagenesis has become increasingly apparent. This growing awareness has created a need for biochemical tools that can be used to identify and characterize potential inhibitors of this enzyme family. In response to this challenge, we have developed a Real-time APOBEC3-mediated DNA Deamination assay. This assay offers a single-step set-up and real-time fluorescent read-out, and it is capable of providing insights into enzyme kinetics. The assay also offers a high-sensitivity and easily scalable method for identifying APOBEC3 inhibitors. This assay serves as a crucial addition to the existing APOBEC3 biochemical and cellular toolkit and possesses the versatility to be readily adapted into a high-throughput format for inhibitor discovery.
Asunto(s)
Citidina Desaminasa , ADN , Humanos , Desaminación , Citidina Desaminasa/metabolismo , ADN/metabolismo , ADN/química , Cinética , Desaminasas APOBEC/metabolismo , Inhibidores Enzimáticos/farmacologíaRESUMEN
RNA binding proteins (RBPs) perform a myriad of functions and are implicated in numerous neurological diseases. To identify the targets of RBPs in small numbers of cells, we developed TRIBE, in which the catalytic domain of the RNA editing enzyme ADAR (ADARcd) is fused to an RBP. When the RBP binds to an mRNA, ADAR catalyzes A to G modifications in the target mRNA that can be easily identified in standard RNA sequencing. In STAMP, the concept is the same except the ADARcd is replaced by the RNA editing enzyme APOBEC. Here we compared TRIBE and STAMP side-by-side in human and Drosophila cells. The goal is to learn the pros and cons of each method so that researchers can choose the method best suited to their RBP and system. In human cells, TRIBE and STAMP were performed using the RBP TDP-43. Although they both identified TDP-43 target mRNAs, combining the two methods more successfully identified high-confidence targets. In Drosophila cells, RBP-APOBEC fusions generated only low numbers of editing sites, comparable to the level of control editing. This was true for two different RBPs, Hrp48 and Thor (Drosophila EIF4E-BP), indicating that STAMP does not work well in Drosophila.
Asunto(s)
Proteínas de Drosophila , Drosophila , Animales , Humanos , Drosophila/genética , Proteínas de Drosophila/metabolismo , ARN Mensajero/genética , ARN Mensajero/metabolismo , Proteínas de Unión al ARN/metabolismo , Proteínas de Unión al ADN/metabolismoRESUMEN
Activation-induced cytidine deaminase (AID) initiates both class switch recombination (CSR) and somatic hypermutation (SHM) in antibody diversification. Mechanisms of AID targeting and catalysis remain elusive despite its critical immunological roles and off-target effects in tumorigenesis. Here, we produced active human AID and revealed its preferred recognition and deamination of structured substrates. G-quadruplex (G4)-containing substrates mimicking the mammalian immunoglobulin switch regions are particularly good AID substrates in vitro. By solving crystal structures of maltose binding protein (MBP)-fused AID alone and in complex with deoxycytidine monophosphate, we surprisingly identify a bifurcated substrate-binding surface that explains structured substrate recognition by capturing two adjacent single-stranded overhangs simultaneously. Moreover, G4 substrates induce cooperative AID oligomerization. Structure-based mutations that disrupt bifurcated substrate recognition or oligomerization both compromise CSR in splenic B cells. Collectively, our data implicate intrinsic preference of AID for structured substrates and uncover the importance of G4 recognition and oligomerization of AID in CSR.
Asunto(s)
Citidina Desaminasa/metabolismo , ADN/metabolismo , Cambio de Clase de Inmunoglobulina , Región de Cambio de la Inmunoglobulina , Recombinación Genética , Desaminasas APOBEC/genética , Desaminasas APOBEC/metabolismo , Animales , Diversidad de Anticuerpos , Linfocitos B/enzimología , Linfocitos B/inmunología , Citidina Desaminasa/química , Citidina Desaminasa/genética , ADN/química , ADN/genética , Humanos , Ratones , Modelos Moleculares , Mutación , Conformación de Ácido Nucleico , Unión Proteica , Conformación Proteica , Bazo/enzimología , Bazo/inmunología , Relación Estructura-Actividad , Especificidad por SustratoRESUMEN
APOBEC3A is an antiviral DNA deaminase often induced by virus infection. APOBEC3A is also a source of cancer mutation in viral and nonviral tumor types. It is therefore critical to identify factors responsible for APOBEC3A upregulation. Here, we test the hypothesis that leaked mitochondrial (mt) double-stranded (ds)RNA is recognized as foreign nucleic acid, which triggers innate immune signaling, APOBEC3A upregulation, and DNA damage. Knockdown of an enzyme responsible for degrading mtdsRNA, the exoribonuclease polynucleotide phosphorylase, results in mtdsRNA leakage into the cytosol and induction of APOBEC3A expression. APOBEC3A upregulation by cytoplasmic mtdsRNA requires RIG-I, MAVS, and STAT2 and is likely part of a broader type I interferon response. Importantly, although mtdsRNA-induced APOBEC3A appears cytoplasmic by subcellular fractionation experiments, its induction triggers an overt DNA damage response characterized by elevated nuclear γ-H2AX staining. Thus, mtdsRNA dysregulation may induce APOBEC3A and contribute to observed genomic instability and mutation signatures in cancer.
Asunto(s)
Citidina Desaminasa , Daño del ADN , Neoplasias , ARN Bicatenario , Humanos , ADN , Neoplasias/genética , ARN Bicatenario/genética , ARN Mitocondrial/genética , Citidina Desaminasa/genéticaRESUMEN
INTRODUCTION: Pseudogenes have been implicated for their role in regulating cellular differentiation and organismal development. However, their role in promoting cancer-associated differentiation has not been well-studied. This study explores the tumour landscape of oesophageal carcinoma to identify pseudogenes that may regulate events of differentiation to promote oncogenic transformation. MATERIALS AND METHOD: De-regulated differentiation-associated pseudogenes were identified using DeSeq2 followed by 'InteractiVenn' analysis to identify their expression pattern. Gene expression dependent and independent enrichment analyses were performed with GSEA and ShinyGO, respectively, followed by quantification of cellular reprogramming, extent of differentiation and pleiotropy using three unique metrics. Stage-specific gene regulatory networks using Bayesian Network Splitting Average were generated, followed by network topology analysis. MEME, STREME and Tomtom were employed to identify transcription factors and miRNAs that play a regulatory role downstream of pseudogenes to initiate cellular reprogramming and further promote oncogenic transformation. The patient samples were stratified based on the expression pattern of pseudogenes, followed by GSEA, mutation analysis and survival analysis using GSEA, MAF and 'survminer', respectively. RESULTS: Pseudogenes display a unique stage-wise expression pattern that characterizes stage II (SII) ESCA with a high rate of cellular reprogramming, degree of differentiation and pleiotropy. Gene regulatory network and associated topology indicate high robustness, thus validating high pleiotropy observed for SII. Pseudogene-regulated expression of SOX2, FEV, PRRX1 and TFAP2A in SII may modulate cellular reprogramming and promote oncogenesis. Additionally, patient stratification-based mutational analysis in SII signifies APOBEC3A (A3A) as a potential hallmark of homeostatic mutational events of reprogrammed cells which in addition to de-regulated APOBEC3G leads to distinct events of hypermutations. Further enrichment analysis for both cohorts revealed the critical role of combinatorial expression of pseudogenes in cellular reprogramming. Finally, survival analysis reveals distinct genes that promote poor prognosis in SII ESCA and patient-stratified cohorts, thus providing valuable prognostic bio-markers along with markers of differentiation and oncogenesis for distinct landscapes of pseudogene expression. CONCLUSION: Pseudogenes associated with the events of differentiation potentially aid in the initiation of cellular reprogramming to facilitate oncogenic transformation, especially during SII ESCA. Despite a better overall survival of SII, patient stratification reveals combinatorial de-regulation of pseudogenes as a notable marker for a high degree of cellular differentiation with a unique mutational landscape.
Asunto(s)
Carcinoma , Citidina Desaminasa , Neoplasias Esofágicas , Proteínas , Humanos , Seudogenes , Teorema de Bayes , Carcinogénesis/genética , Neoplasias Esofágicas/genética , Reprogramación Celular , Carcinoma/genética , Proteínas de Homeodominio/genéticaRESUMEN
APOBEC proteins can deaminate cytosine residues in DNA and RNA. This can lead to somatic mutations, DNA breaks, RNA modifications, or DNA demethylation in a selective manner. APOBECs function in various cellular compartments and recognize different nucleic acid motifs and structures. They orchestrate a wide array of genomic and epigenomic modifications, thereby affecting various cellular functions positively or negatively, including immune editing, viral and retroelement restriction, DNA damage responses, DNA demethylation, gene expression, and tissue homeostasis. Furthermore, the cumulative increase in genomic and epigenomic editing with aging could also, at least in part, be attributed to APOBEC function. We synthesize our cumulative understanding of APOBEC activity in a unifying overview and discuss their genomic and epigenomic impact in physiological, pathological, and technological contexts.
Asunto(s)
Desaminasas APOBEC , Epigenómica , Desaminasas APOBEC/genética , Desaminasas APOBEC/metabolismo , Citidina Desaminasa/genética , Citidina Desaminasa/metabolismo , Genoma , Genómica , RetroelementosRESUMEN
Programmable RNA cytidine deamination has recently been achieved using a bifunctional editor (RESCUE-S) capable of deaminating both adenine and cysteine. Here, we report the development of "CURE", the first cytidine-specific C-to-U RNA Editor. CURE comprises the cytidine deaminase enzyme APOBEC3A fused to dCas13 and acts in conjunction with unconventional guide RNAs (gRNAs) designed to induce loops at the target sites. Importantly, CURE does not deaminate adenosine, enabling the high-specificity versions of CURE to create fewer missense mutations than RESCUE-S at the off-targets transcriptome-wide. The two editing approaches exhibit overlapping editing motif preferences, with CURE and RESCUE-S being uniquely able to edit UCC and AC motifs, respectively, while they outperform each other at different subsets of the UC targets. Finally, a nuclear-localized version of CURE, but not that of RESCUE-S, can efficiently edit nuclear RNAs. Thus, CURE and RESCUE are distinct in design and complementary in utility.