Regulation of APOBEC3 cytidine deaminase-induced mutation during cancerdevelopment

摘要 APOBEC特征突变(TCA和TCT三核苷酸中的C到T和C到G替换 序列)构成人类癌症中第二丰富的突变特征。这个签名是 由APOBEC胞苷脱氨酶家族的几个成员的异常活性引起的，正常情况下 在许多细胞过程中发挥作用，包括限制病毒。最近，我们发现APOBEC3A (A3A)在APOBEC突变的乳腺癌细胞系中表达升高，导致细胞数量增加 胞苷脱氨酶活性与乳腺癌诱变这项提案的目标是将 新发现的APOBEC突变特征成分，决定了A3A mRNA的表达方式 在癌症中上调，确定蛋白酶体对A3A蛋白丰度的控制，并表征DNA修复 限制A3A突变的途径。AIM1将确定A3A的原因和后果--和 APOBEC3B诱导的插入/缺失突变。目标2将描述导致异常的机制 通过确定转录因子和信号通路上调A3A在乳腺癌中的表达 负责增加A3A的表达。此外，我们还将调查(S)导致 蛋白酶体依赖的A3A降解并评估后缺陷的突变后果 A3A丰度的翻译调控。AIM3将表征同源化合物的抗突变作用 重组蛋白BRCA1和BRCA2在模板开关介导的A3A依赖的ABASIC旁路中的作用 位于复制分叉的站点。我们将确定BRCA1或BRCA2缺乏是否会增加APOBEC诱导的 在人类细胞系中的突变，并从基因上定义参与该途径的其他蛋白质。成功 这些目标的完成将增强我们对A3A调控及其在癌症病因学中的作用的理解。 此外，这些努力将确定限制APOBEC诱导的突变的方法，这可能提供 通过限制导致耐药性的持续肿瘤进化而带来的治疗益处。

Abstract APOBEC signature mutations (C to T and C to G substitutions in TCA and TCT trinucleotide sequences) comprise the second most abundant mutation signature in human cancers. This signature is caused by aberrant activity of several members of the APOBEC family of cytidine deaminases, which normally function in many cellular processes including the restriction of viruses. Recently, we found that APOBEC3A (A3A) expression is elevated in APOBEC-mutated breast cancer cell lines, resulting in increased cellular cytidine deaminase activity and breast cancer mutagenesis. The objectives of this proposal are to characterize newly identified components of the APOBEC mutation signature, determine how A3A mRNA expression is upregulated in cancer, define proteasomal controls on A3A protein abundance, and characterize DNA repair pathways that limit A3A mutagenesis. Aim1 will determine the causes and consequences of A3A- and APOBEC3B-induced insertion/deletion mutations. Aim 2 will characterize the mechanisms leading to aberrant up-regulation of A3A in breast cancers by identifying the transcription factors and signaling pathways responsible for increasing A3A expression. Additionally, we will investigate the mechanism(s) leading to proteasome-dependent degradation of A3A and assess the mutagenic consequences of defective post- translational control of A3A abundance. Aim3 will characterize anti-mutagenic roles of the homologous recombination proteins BRCA1 and BRCA2 in template switch-mediated bypass of A3A-dependent abasic sites at replication forks. We will determine whether BRCA1 or BRCA2-deficiency elevates APOBEC-induced mutation in human cell lines and genetically define additional proteins involved in the pathway. Successful completion of these aims will enhance our understanding of A3A regulation and its role in cancer etiology. Additionally, these efforts will identify means to limit APOBEC-induced mutagenesis, which could provide therapeutic benefit by limiting continued tumor evolution that leads to drug resistance.