How does TREX2 maintain and alter chromosomes?

描述(申请人提供)：基因组不稳定是癌症的一个标志。然而，基因组的维持和基因组不稳定的机制尚不清楚。这项提议延续了圣安东尼奥健康科学中心的保罗·哈蒂斯博士和纽约阿尔伯特·爱因斯坦医学院的克里斯蒂娜·蒙塔尼亚博士之间的合作。他们将探索TREX2在基因组不稳定性的抑制和发展中的作用。TREX2是一种3‘？5’核酸外切酶，可消除DNA中的3‘错配。然而，它的生物学功能尚不清楚。我们发现TREX2缺失增加了等色单体断裂和总染色体重排(GCRs)的水平，这表明TREX2保持了完整的染色体结构；然而，我们也发现TREX2融合了错配的反向重复序列来诱导回文染色体，这些染色体不稳定，容易涉及多条染色体的持续重排。此外，我们发现TREX2使易癌细胞的基因组不稳定。因此，TREX2既保持了基因组的完整性，又改变了基因组的完整性。然而，目前尚不清楚TREX2是如何实现这些相反的结果的。由于TREX2的缺失导致DNA断裂和重排，我们认为它参与了DNA双链断裂(DSB)的修复。然而，TREX2缺失的细胞具有更高的DSB修复能力。因此，我们假设TREX2通过维持复制叉(RF)来抑制DSB的形成。为了支持这一假说，我们发现TREX2与无错复制后修复(EF-PRR)途径中的蛋白质相关，并使增殖细胞核抗原(增殖细胞核抗原)泛素化；这是一种关键的EF-PRR功能，通过两种机制抑制RF停滞：跨损伤合成和模板切换。我们希望进一步调查这些问题。在目标1中，我们将解决我们的假设，即TREX2通过EF-PRR介导的病变旁路抑制DSB的形成和GCR的形成，在目标2中，我们将解决我们的假设，即TREX2通过EF-PRR及其与其他肿瘤抑制通路的遗传整合而使基因组不稳定。最后，在目标3中，我们建议在小鼠体内改变TREX2，以观察其在整个动物中的生物学功能。这些研究将阐明TREX2在保持和改变基因组完整性方面所起的双重作用，并将为抑制和创造导致癌症的基因组不稳定性提供机械学上的见解。这些知识将有助于评估TREX2作为抗癌药物靶点。

DESCRIPTION (provided by applicant): Genome instability is a hallmark of cancer. Yet genome maintenance and mechanisms of genome instability are not clearly understood. This proposal continues the collaboration between Dr. Paul Hasty at the Health Science Center at San Antonio and Dr. Cristina Montagna at Albert Einstein College of Medicine in New York. They will explore the involvement of TREX2 in both the suppression and development of genomic instability. TREX2 is a 3'?5' exonuclease that removes 3' mismatches in DNA. However, its biological function is not known. We found that TREX2-deletion increased the level of isochromatid breaks and gross chromosomal rearrangements (GCRs) demonstrating that TREX2 maintains intact chromosome structure; however, we also found that TREX2 fused mismatch inverted repeats to induce palindromic chromosomes that were unstable and susceptible to continual rearrangements that involve multiple chromosomes. In addition, we found that TREX2 enables genomic instability in cancer prone cells. Thus, TREX2 both maintains and alters genome integrity. Yet just how TREX2 accomplishes these antithetical outcomes is not known. Since TREX2 deletion caused breaks and rearrangements, we thought it participated in DNA double strand break (DSB) repair. However, TREX2-deleted cells have elevated DSB repair capacity. Therefore, we hypothesized that TREX2 suppressed the formation of DSBs by maintaining replication forks (RFs). To support this hypothesis, we found TREX2 associated with proteins in the error-free postreplication repair (EF-PRR) pathway and enabled PCNA (proliferating cell nuclear antigen) ubiquitination; a key EF-PRR function that suppresses RF stalling through two mechanisms: translesion synthesis and template switch. We wish to further these investigations. In Aim 1 we will address our hypothesis that TREX2 suppresses DSB formation and GCRs though EF-PRRmediated lesion bypass and in Aim 2 we will address our hypothesis that TREX2 enables genomic instability through EF-PRR and its genetic integration with other tumor suppressor pathways. Finally in Aim 3 we propose to alter TREX2 in mice to observe its biological function in the whole animal. These studies will elucidate the dual role that TREX2 plays in preserving and altering genomic integrity and will provide mechanistic insight to both the suppression and creation of genomic instability that causes cancer. Such knowledge will be useful to evaluate TREX2 as an anti-cancer drug target.