RNA-remodeling proteins, including RNA helicases and chaperones, play vital roles in the remodeling of structured RNAs. During viral replication, viruses require RNA-remodeling proteins to facilitate proper folding and/or re-folding the viral RNA elements. Coxsackieviruses B3 (CVB3) and Coxsackieviruses B5 (CVB5), belonging to the genus Enterovirus in the family Picornaviridae, have been reported to cause various infectious diseases such as hand-foot-and-mouth disease, aseptic meningitis, and viral myocarditis. However, little is known about whether CVB3 and CVB5 encode any RNA remodeling proteins. In this study, we showed that 2C proteins of CVB3 and CVB5 contained the conserved SF3 helicase A, B, and C motifs, and functioned not only as RNA helicase that unwound RNA helix bidirectionally in an NTP-dependent manner, but also as RNA chaperone that remodeled structured RNAs and facilitated RNA strand annealing independently of NTP. In addition, we determined that the NTPase activity and RNA helicase activity of 2C proteins of CVB3 and CVB5 were dependent on the presence of divalent metallic ions. Our findings demonstrate that 2C proteins of CVBs possess RNA-remodeling activity and underline the functional importance of 2C protein in the life cycle of CVBs.

RNA 重塑蛋白，包括 RNA 解旋酶和分子伴侣，在结构化 RNA 的重塑中起着至关重要的作用。在病毒复制过程中，病毒需要 RNA 重塑蛋白来促进病毒 RNA 元件的正确折叠和/或重新折叠。柯萨奇病毒 B3 (CVB3) 和柯萨奇病毒 B5 (CVB5)，属于小核糖核酸病毒科肠道病毒属，据报道可引起手足口病、无菌性脑膜炎、病毒性心肌炎等多种传染病。然而，关于 CVB3 和 CVB5 是否编码任何 RNA 重塑蛋白知之甚少。在这项研究中，我们发现 CVB3 和 CVB5 的 2C 蛋白含有保守的 SF3 解旋酶 A、B 和 C 基序，不仅作为 RNA 解旋酶以 NTP 依赖性方式双向解开 RNA 螺旋，而且还作为 RNA 伴侣。重构了结构化的 RNA 并促进了独立于 NTP 的 RNA 链退火。此外，我们确定 CVB3 和 CVB5 的 2C 蛋白的 NTPase 活性和 RNA 解旋酶活性取决于二价金属离子的存在。