Mechanisms of genome instability induced by APOBEC Cytidine Deaminases and its impacts during cancer development.

摘要 APOBEC家族胞苷脱氨酶是癌症基因组的主要突变者，通常会导致 在受影响的肿瘤中有数千个C到T碱基的替换。这些酶通常在体内发挥作用 免疫系统和脂类代谢。载脂蛋白BEC如何变得失调以及随后的作用 APOBEC诱导的遗传不稳定性在促进癌症进展方面的作用尚不清楚。同样不为人知的是 除引起碱基替换外，载脂蛋白BECs是否还会导致肿瘤中其他类型的遗传不稳定性 通过脱氨作用。这项提案总体目标是确定使APOBEC能够 突变，确定这种活动如何改变癌症基因组，并评估这种基因的贡献 不稳定致癌。目标1将确定是否由化学物质引起的单链DNA水平增加 癌基因诱导的复制应激促进APOBEC的突变。我们将衡量以下方面的影响 复制应激对APOBEC诱导的人类细胞突变频率的影响，决定了癌细胞 显示内源性APOBEC活性也显示复制应激标志，并确定 Her2激活诱导的复制应激与APOBEC突变协同改变细胞增殖 并在小鼠模型中加速肿瘤的形成。目标2将解决染色质修饰剂的缺陷 影响APOBEC的诱变。我们已经确定染色质修饰酶的丢失，这些酶是 在癌症发展过程中也经常失活，增加APOBEC诱导突变的频率 放在酵母里。这种效应背后的机制将被确定，并在人类细胞中重新投降。 此外，染色质修饰物丢失与APOBEC诱导的数量增加之间的关联 对测序癌症中的突变将进行生物信息学评估。AIM 3将调查APOBEC 能够在癌症发展过程中诱导染色体重排。我们将衡量 APOBEC在酵母和人中诱导的非等位基因重组频率和拷贝数变异 细胞以及评估APOBECs是否会诱变在 这些重组事件导致了Kataegis。在这些目标中提出的实验结果将 可能表明，突变驱动的、与癌症相关的DNA代谢变化增加了APOBEC- 诱导突变，研究载脂蛋白BECs在促进其他类型基因的扩大作用 改变，并直接表征APOBEC产生的突变促进肿瘤形成的能力。 成功完成这些目标将描述一个关键方面的发展和进展 相当数量的人类肿瘤。

Abstract APOBEC family cytidine deaminases are prominent mutators of cancer genomes, often causing thousands of C to T base substitutions in affected tumors. These enzymes normally function within the immune system and lipid metabolism. How APOBECs become dysregulated and the role subsequent of APOBEC-induced genetic instability has in promoting cancer progression are unclear. Also unknown is whether APOBECs induce other types of genetic instability in tumors in addition to base substitutions caused by deamination. The overall objective of this proposal is to identify mechanisms that enable APOBEC mutagenesis, determine how this activity alters cancer genomes, and assess the contribution of this genetic instability to carcinogenesis. Aim 1 will determine if increased levels of single strand DNA caused by chemical and oncogene-induced replication stress facilitates APOBEC mutagenesis. We will measure the effects of replication stress on APOBEC-induced mutation frequencies in human cells, determine if cancer cells displaying endogenous APOBEC activity also display markers of replication stress, and determine whether replication stress induced by Her2 activation synergizes with APOBEC mutagenesis to alter cell proliferation and accelerate tumorigenesis in a mouse model. Aim 2 will address how deficiencies in chromatin modifiers influence APOBEC mutagenesis. We have determined that loss of chromatin modifying enzymes, which are also frequently inactivated during cancer development, increase the frequency of APOBEC-induced mutations in yeast. The mechanisms underlying this effect will be determined and re-capitulated in human cells. Additionally, associations between chromatin modifier loss and elevated numbers of APOBEC-induced mutations in sequenced cancers will be bioinformatically evaluated. Aim 3 will investigate whether APOBECs are capable of inducing chromosomal rearrangements during cancer development. We will measure APOBEC-induced frequencies of non-allelic recombination and copy number variation in yeast and human cells as well as evaluate whether APOBECs mutagenize the single strand DNA intermediates formed during these recombination events to cause kataegis. The results from the experiments proposed in these Aims will likely demonstrate that mutation-driven, cancer-associated changes in DNA metabolism increase APOBEC- induced mutagenesis, investigate an expanded role for APOBECs in promotion of additional types of genetic alterations, and directly characterize the ability of APOBEC-generated mutagenesis to promote tumorigenesis. Successful completion of these aims will describe a critical aspect in the development and progression of a significant number of human tumors.