How does TREX2 maintain and alter chromosomes?

描述（由申请人提供）：基因组不稳定性是癌症的标志。然而，基因组的维护和基因组不稳定性的机制还没有清楚地了解。该提案延续了圣安东尼奥健康科学中心的Paul Hasty博士和纽约阿尔伯特爱因斯坦医学院的Cristina Montagna博士之间的合作。他们将探索TREX 2在基因组不稳定性的抑制和发展中的参与。TREX 2是一个3 '？去除DNA中3'错配的5'外切核酸酶。但其生物学功能尚不清楚。我们发现TREX 2缺失增加了等染色单体断裂和总染色体重排（GCR）的水平，表明TREX 2保持了完整的染色体结构;然而，我们还发现TREX 2融合错配反向重复序列以诱导回文染色体，这些回文染色体不稳定并且容易发生涉及多条染色体的连续重排。此外，我们发现TREX 2使癌症易感细胞中的基因组不稳定。因此，TREX 2既维持又改变基因组的完整性。然而，TREX 2如何实现这些对立的结果尚不清楚。由于TREX 2的缺失导致了DNA的断裂和重排，我们认为它参与了DNA双链断裂（DSB）的修复。然而，TREX 2缺失的细胞具有升高的DSB修复能力。因此，我们假设TREX 2通过维持复制叉（RF）来抑制DSB的形成。为了支持这一假设，我们发现TREX 2与无错误复制后修复（EF-PRR）途径中的蛋白质相关，并使PCNA（增殖细胞核抗原）泛素化;一种关键的EF-PRR功能，通过两种机制抑制RF停滞：translesion合成和模板转换。我们希望进一步开展这些调查。在目标1中，我们将阐述我们的假设，即TREX 2通过EF-PRR介导的病变旁路抑制DSB形成和GCR，在目标2中，我们将阐述我们的假设，即TREX 2通过EF-PRR及其与其他肿瘤抑制途径的遗传整合实现基因组不稳定性。最后，在目标3中，我们提出在小鼠中改变TREX 2以观察其在整个动物中的生物学功能。这些研究将阐明TREX 2在保护和改变基因组完整性方面发挥的双重作用，并将为抑制和创造导致癌症的基因组不稳定性提供机制性见解。这些知识将有助于评估TREX 2作为抗癌药物靶标。

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.