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体，通常引起癌症。 在受影响的肿瘤中有数千个C到T碱基的替换。这些酶通常在细胞内起作用。 免疫系统和脂质代谢。APOBECs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中的作用尚不清楚。同样未知的是 APOBECs是否诱导肿瘤中除了碱基取代以外的其他类型的遗传不稳定性， 通过脱氨基作用。本提案的总体目标是确定使APOBEC能够 突变，确定这种活性如何改变癌症基因组，并评估这种遗传突变的贡献。 不稳定性致癌。目标1将确定是否由化学物质引起的单链DNA水平增加 并且癌基因诱导的复制应激促进APOBEC诱变。我们将测量 复制压力对APOBEC诱导的人类细胞突变频率的影响，确定癌细胞是否 显示内源性APOBEC活性也显示复制应激的标志物，并确定是否 Her 2激活诱导的复制应激与APOBEC诱变协同作用以改变细胞增殖 并加速小鼠模型中的肿瘤发生。目的2将解决如何在染色质修饰缺陷 影响APOBEC诱变。我们已经确定，染色质修饰酶的丢失， 在癌症发展过程中也经常失活，增加APOBEC诱导突变的频率 在酵母中。这种作用的机制将在人类细胞中确定和重新投降。 此外，染色质修饰剂丢失与APOBEC诱导的凋亡数量增加之间的相关性， 将对测序癌症中的突变进行生物信息学评估。目标3将研究APOBECs是否 能够在癌症发展过程中诱导染色体重排。我们将测量 APOBEC诱导的酵母和人类非等位基因重组和拷贝数变异频率 细胞以及评估APOBECs是否诱变在细胞内形成的单链DNA中间体。 这些重组事件导致Kataegis。这些目标中提出的实验结果将 可能表明，突变驱动的，癌症相关的DNA代谢变化增加APOBEC- 诱导诱变，研究APOBECs在促进其他类型的遗传 改变，并直接表征APOBEC产生的诱变促进肿瘤发生的能力。 成功完成这些目标将描述一个发展和进步的关键方面， 大量的人类肿瘤。

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.