Deciphering pathways involved in topoisomerase II turnover

项目总结 DNA拓扑异构酶是一类可以通过瞬间特异地分解拓扑应力的酶 在DNA分子中引入链断裂，使超螺旋DNA链能够旋转。 哺乳动物细胞编码两种类型的拓扑异构酶：I型拓扑异构酶(TOP1、TOP1mt、TOP3A和 TOP3B)，将单链断裂引入DNA，以及II型拓扑异构酶(TOP2A、TOP2B和 SPO11)，将双链断裂(DSB)引入DNA。本提案侧重于第二类 人类体细胞中的拓扑异构酶，即TOP2A/2B。 在切割反应中，TOP2催化活性部位的酪氨酸共价连接到 DNA骨架并形成所谓的拓扑异构酶II裂解复合体(TOP2cc)。低于正常 在这种情况下，TOP2cc是暂时形成的，无法检测到。然而，各种各样的拓扑异构酶毒物， 包括依托泊苷，已被开发并用作癌症治疗的化疗药物。 从机制上讲，依托泊苷可以稳定TOP2cc，最终导致DNA链断裂并杀死肿瘤 细胞。 虽然包括我们在内的许多调查人员调查了TOP2诱导的DNA损伤以及它们如何 通过不同的修复途径修复，这一建议侧重于一个新的概念，即细胞已经进化成不同的 避免和限制TOP2引起DNA损伤的途径。在这项提案中，我们将机械地确定 几种独特的TOP2调节因子如何共同作用以避免DNA损伤，从而促进细胞存活。 这些研究的结果对于了解依托泊苷的治疗反应至关重要。 以及其他抗癌药物。 。

PROJECT SUMMARY DNA topoisomerases are types of enzymes that can specifically resolve topological stresses by transiently introducing strand breaks into DNA molecules and enabling the rotation of the supercoiled DNA strand. Mammalian cells encode two types of topoisomerases: type I topoisomerases (TOP1, TOP1mt, TOP3A, and TOP3B), which introduce single strand breaks into DNA, and type II topoisomerases (TOP2A, TOP2B, and SPO11), which introduce double strand breaks (DSBs) into DNA. This proposal focuses on type II topoisomerases, i.e. TOP2A/2B, in human somatic cells. During cleavage reaction, the tyrosine in the catalytic active site of TOP2 is covalently linked to the DNA backbone and forms the so-called topoisomerase II cleavage complex (TOP2cc). Under normal conditions, TOP2cc forms transiently and is not detectable. However, a wide variety of topoisomerase poisons, including etoposide, have been developed and used as chemotherapeutic drugs for cancer treatment. Mechanistically, etoposide acts to stabilize TOP2cc, which eventually lead to DNA strand breaks and kill tumor cells. While many investigators including us investigated TOP2-induced DNA lesions and how they can be repaired by different repair pathways, this proposal focuses on a new concept that cells have evolved distinct pathways to avoid and limit DNA lesions induced by TOP2. In this proposal, we will determine mechanistically how several unique TOP2 regulators act together to avoid DNA damage and therefore promote cell survival. Results from these studies are critically important for the understanding of therapeutic response to etoposide and other anti-cancer agents. .