State Key Laboratory of Crop Stress Biology for Arid Areas and College of Life Sciences, Northwest A&F University, Yangling, Shaanxi, China; Experimental Medicine Center, The Affiliated Hospital of Southwest Medical University, Luzhou, Sichuan, China; Department of Endocrinology and Metabolism, and Cardiovascular and Metabolic Diseases Key Laboratory of Luzhou, and Sichuan Clinical Research Center for Nephropathy, and Academician (Expert) Workstation of Sichuan Province, The Affiliated Hospital of Southwest Medical University, Luzhou, Sichuan, China.
State Key Laboratory of Crop Stress Biology for Arid Areas and College of Life Sciences, Northwest A&F University, Yangling, Shaanxi, China.
J Biol Chem. 2020 Dec 18;295(51):17646-17658. doi: 10.1074/jbc.RA120.015492.
RecQ family helicases are highly conserved from bacteria to humans and have essential roles in maintaining genome stability. Mutations in three human RecQ helicases cause severe diseases with the main features of premature aging and cancer predisposition. Most RecQ helicases shared a conserved domain arrangement which comprises a helicase core, an RecQ C-terminal domain, and an auxiliary element helicase and RNaseD C-terminal (HRDC) domain, the functions of which are poorly understood. In this study, we systematically characterized the roles of the HRDC domain in E. coli RecQ in various DNA transactions by single-molecule FRET. We found that RecQ repetitively unwinds the 3'-partial duplex and fork DNA with a moderate processivity and periodically patrols on the ssDNA in the 5'-partial duplex by translocation. The HRDC domain significantly suppresses RecQ activities in the above transactions. In sharp contrast, the HRDC domain is essential for the deep and long-time unfolding of the G4 DNA structure by RecQ. Based on the observations that the HRDC domain dynamically switches between RecA core- and ssDNA-binding modes after RecQ association with DNA, we proposed a model to explain the modulation mechanism of the HRDC domain. Our findings not only provide new insights into the activities of RecQ on different substrates but also highlight the novel functions of the HRDC domain in DNA metabolisms.
RecQ 家族解旋酶在从细菌到人类的范围内高度保守，对维持基因组稳定性具有重要作用。三种人类 RecQ 解旋酶的突变会导致严重疾病，主要特征为过早衰老和癌症易感性。大多数 RecQ 解旋酶具有保守的结构域排列，包括解旋酶核心、RecQ C 末端结构域和辅助元件解旋酶和核糖核酸酶 D C 末端（HRDC）结构域，但其功能知之甚少。在这项研究中，我们通过单分子 FRET 系统地研究了 HRDC 结构域在各种 DNA 反应中在大肠杆菌 RecQ 中的作用。我们发现 RecQ 以适度的持续性反复解开 3'-部分双链体和分叉 DNA，并通过易位在 5'-部分单链 DNA 上周期性地巡逻。HRDC 结构域显著抑制了 RecQ 在上述反应中的活性。与此形成鲜明对比的是，HRDC 结构域对于 RecQ 对 G4 DNA 结构的深入和长时间展开是必不可少的。根据 HRDC 结构域在 RecQ 与 DNA 结合后在 RecA 核心和 ssDNA 结合模式之间动态切换的观察结果，我们提出了一个模型来解释 HRDC 结构域的调节机制。我们的发现不仅为 RecQ 在不同底物上的活性提供了新的见解，还突出了 HRDC 结构域在 DNA 代谢中的新功能。
