Mechanical regulation of the helicase activity of Zika virus NS3

Xiaocong Cao,. et al.’s published a new article titled “Mechanical regulation of the helicase activity of Zika virus NS3”, was accepted byBiophysical Journal on July 25, 2022 and became online on August 02, 2022. https://www.cell.com/biophysj/fulltext/S0006-3495(22)00603-8

Xiaocong Cao and Kaixian Liu are the co-first authors.

Professors Tengchuan Jin and Shixin Liu are corresponding authors.

Keywords: Zika virus; NS3 helicase; optical tweezers

Zika virus (ZIKV) is a positive-sense single-stranded RNA virus that infects humans and can cause birth defects and neurological disorders. Its non-structural protein 3 (NS3) contains a protease domain and a helicase domain, both of which play essential roles during the viral life cycle. However, it has been shown that ZIKV NS3 has an inherently weak helicase activity, making it unable to unwind long RNA duplexes alone. How this activity is stimulated to process the viral genome and whether the two domains of NS3 are functionally coupled remain unclear. In this study, we used optical tweezers to characterize the RNA-unwinding properties of ZIKV NS3—including its processivity, velocity, and step size—at the single-molecule level. We found that external forces that weaken the stability of the duplex RNA substrate significantly enhance the helicase activity of ZIKV NS3. On the other hand, we showed that the protease domain increases the binding affinity of NS3 to RNA but has only a minor effect on unwinding per se. Our findings suggest that the ZIKV NS3 helicase is activated on demand in the context of viral replication, a paradigm that may be generalizable to other flaviviruses.

2022年8月2日，金腾川课题组与美国洛克菲勒大学刘诗欣课题组合作在Biophysical Journal杂志在线发表题为“Mechanical regulation of the helicase activity of Zika virus NS3”的研究论文。金腾川课题组曹晓聪和刘诗欣课题组Kaixian Liu为本文共同第一作者；金腾川教授和刘诗欣教授为本文共同通讯作者。

 寨卡病毒(ZIKV) 是一种正向单链RNA 病毒，可感染人类并导致新生儿小头畸形及格林-巴利综合症等神经系统病变。寨卡病毒非结构蛋白NS3蛋白包含N端丝氨酸蛋白酶结构域和C端解旋酶结构域，这两者在病毒生命周期中都发挥着重要作用，是重要的抗病毒靶标。先前研究表明NS3的固有解旋酶活性较弱（不能解旋超过20 bp dsRNA），它如何在病毒复制周期中处理长RNA 基因组的机制不清楚；NS3 的两种酶活性（蛋白酶和解旋酶）对于病毒组装和复制是必不可少的，但目前尚不清楚这两个有不同功能的结构域是否会相互影响。

 该研究使用光学镊子在单分子水平上表征ZIKV NS3 的RNA 展开特性，包括其持续解旋能力、解旋速度和步长。使用光镊在RNA 底物末端施加作用力来削弱RNA 底物的稳定性，发现这一机械刺激显著增强了ZIKV NS3 的RNA 解旋活性。另一方面发现蛋白酶结构域增加了NS3 与RNA 的结合亲和力，但对解旋活性的影响很小。这一研究为理解ZIKV NS3 在细胞中的活性调节提供了生物物理学基础，NS3在病毒复制的背景下按需激活，这种模式可能可以推广到其他黄病毒。

 全文链接：

https://www.cell.com/biophysj/fulltext/S0006-3495(22)00603-8