Department of Biochemistry, School of Medicine, Southern University of Science and Technology, Shenzhen, China.
Department of Rheumatology and Immunology, Shenzhen People's Hospital, Shenzhen, Guangdong, China; The First Affiliated Hospital, Southern University of Science and Technology, Shenzhen, Guangdong, China.
J Biol Chem. 2024 Aug;300(8):107592. doi: 10.1016/j.jbc.2024.107592. Epub 2024 Jul 18.
MLH1 plays a critical role in DNA mismatch repair and genome maintenance. MLH1 deficiency promotes cancer development and progression, but the mechanism underlying MLH1 regulation remains enigmatic. In this study, we demonstrated that MLH1 protein is degraded by the ubiquitin-proteasome system and have identified vital cis-elements and trans-factors involved in MLH1 turnover. We found that the region encompassing the amino acids 516 to 650 is crucial for MLH1 degradation. The mismatch repair protein PMS2 may shield MLH1 from degradation as it binds to the MLH1 segment key to its turnover. Furthermore, we have identified the E3 ubiquitin ligase UBR4 and the deubiquitylase USP5, which oppositely modulate MLH1 stability. In consistence, UBR4 or USP5 deficiency affects the cellular response to nucleotide analog 6-TG, supporting their roles in regulating mismatch repair. Our study has revealed important insights into the regulatory mechanisms underlying MLH1 proteolysis, critical to DNA mismatch repair related diseases.
MLH1 在 DNA 错配修复和基因组维护中发挥着关键作用。MLH1 缺陷会促进癌症的发生和发展，但 MLH1 调节的机制仍然神秘。在这项研究中，我们证明 MLH1 蛋白被泛素-蛋白酶体系统降解，并确定了参与 MLH1 周转的重要顺式元件和反式因子。我们发现，包含氨基酸 516 到 650 的区域对于 MLH1 的降解至关重要。错配修复蛋白 PMS2 可能通过与关键的 MLH1 片段结合来保护 MLH1 免受降解。此外，我们已经鉴定出 E3 泛素连接酶 UBR4 和去泛素酶 USP5，它们分别调节 MLH1 的稳定性。一致地，UBR4 或 USP5 的缺乏会影响细胞对核苷酸类似物 6-TG 的反应，支持它们在调节错配修复中的作用。我们的研究揭示了 MLH1 蛋白水解的调控机制的重要见解，这对与 DNA 错配修复相关的疾病至关重要。
