Project description:<p><b>Reprinted from Roberts et al. "An APOBEC cytidine deaminase mutagenesis pattern is widespread in human cancers", Nature Genetics, 45:970-976, 2013, with permission of Nature Publishing Group:</b></p> <p>Recent studies indicate that a subclass of APOBEC cytidine deaminases, which convert cytosine to uracil during RNA editing and retrovirus or retrotransposon restriction, may induce mutation clusters in human tumors. We show here that throughout cancer genomes APOBEC-mediated mutagenesis is pervasive and correlates with APOBEC mRNA levels. Mutation clusters in whole-genome and exome data sets conformed to the stringent criteria indicative of an APOBEC mutation pattern. Applying these criteria to 954,247 mutations in 2,680 exomes from 14 cancer types, mostly from The Cancer Genome Atlas (TCGA), showed a significant presence of the APOBEC mutation pattern in bladder, cervical, breast, head and neck, and lung cancers, reaching 68% of all mutations in some samples. Within breast cancer, the HER2-enriched subtype was clearly enriched for tumors with the APOBEC mutation pattern, suggesting that this type of mutagenesis is functionally linked with cancer development. The APOBEC mutation pattern also extended to cancer-associated genes, implying that ubiquitous APOBEC-mediated mutagenesis is carcinogenic.</p>
Project description:Interventions: Blood samples(10 points) are collected after the first administration of capecitabine for pharmacokinetic analysis and cytidine deaminase activity measurement.
Primary outcome(s): To evaluate the correlation AUC of 5-DFUR/AUC of 5-DFCR ratio and cytidine deaminase activity.
Study Design: Single arm Non-randomized
Project description:This study evaluates the similarity of adaptive immune mechanisms between jawless and jawed vertebrates using lamprey cytidine deaminase (CDA). We identified the ancestral gene Lr-CDAs of the AID/APOBEC deaminase family and evaluated its biological function in vivo. Lr-CDA1 deletion affected the assembly of three types of variable lymphocyte receptors (VLRs). We identified a switch-like region in lamprey gVLRs bound to Lr-CDAs, which upon repression, downregulated VLRB expression. Overall, we propose that lampreys have an early form of class switch recombination (CSR) that is mediated by Lr-CDAs and acts on gVLRs, affecting the assembly, maturation, and diversity regulation of VLR genes in Lethenteron reissneri. This CSR process in lampreys is linked to tumorigenesis and chromosomal translocation markers via Lr-CDAs.
Project description:Intratumoral genetic heterogeneity and mutational burden have been suggested to be the fuel and the source of resistance for many molecularly targeted therapies throughout a multitude of cancers. Emerging evidence indicates that tumor cells could hijack the powerful mutagenesis machinery mediated by the DNA deaminase APOBEC family proteins to intensify mutagenesis, promote intratumoral heterogeneity, and foster therapy resistance through a cell-autonomous mechanism. However, this mechanism has yet to be characterized. Utilizing prostate cancer (PCa) as a relevant model, we have identified the Synaptotagmin Binding Cytoplasmic RNA Interacting Protein (SYNCRIP) as a molecular brake for APOBEC-driven mutagenesis, intratumoral heterogeneity, and resistance to Androgen Receptor (AR) targeted therapies. Through a multi-disciplinary approach integrating bulk and single cell RNA-Seq (scRNA-Seq), whole-genome exome-sequencing (WES), and CRISPR library screening, we identified eight mutated resistance driver genes and revealed unparalleled details of how these heterogeneously aberrant subclones fuel the evolution of AR therapy resistance. For the first time, these findings exposed a cell-autonomous mechanism activating APOBEC-driven mutagenesis, consequently fueling mutational burden, genetic heterogeneity, and therapy resistance, and suggested that APOBEC proteins could be the potential therapeutic targets for preventing or overcoming resistance in PCa.
Project description:We report the analysis of genome wide distribution of activation induced cytidine deaminase by ChIP-seq in Human B cells. The resultant distribution of AID has then been compared to various histone modifications and transcription factors to shed insights into the mechanisms that target this enzyme.
Project description:The AID (activation induced deaminase)/APOBEC (apolipoprotein B mRNA editing catalytic polypeptide-like) family of proteins are zinc-dependent cytidine deaminases active on polynucleotides and involved in RNA editing, DNA demethylation or DNA editing. The enzymatic activity, substrate or physiological target(s) of APOBEC2, a member of the AID/APOBEC, remain elusive. Here, we combined next generation sequencing (NGS) techniques with state-of-the-art molecular biology to comprehensively examine the physiological effects of APOBEC2 on the transcriptome and methylome using C2C12 myoblasts differentiating in culture. We also examined APOBEC2’s genome wide-binding specificity. Using RNA sequencing (RNA-seq) by polyA capture, we detected no evidence that APOBEC2 is an RNA editor. In the same system, enhanced reduced representation bisulfite sequencing (eRRBS) data did not support the proposed role of APOBEC2 as a 5-methyl-C (5mC) deaminase. However, chromatin immunoprecipitation sequencing (ChIP-Seq) did reveal specific locations of genomic occupancy of APOBEC2 with a specific motif preference. Combining biochemical, ChIP-Seq and RNA-Seq gene expression analyses we demonstrate that APOBEC2 acts as a negative regulator of gene expression in muscle cells. Our data support a model of APOBEC2 acting as a chromatin-binding factor that leads to inhibition of transcription of genes involved in cell cycle regulation during C2C12 differentiation.