Yang Chee-Hing, Wu Cheng-Hao, Lo Shih-Yen, Lua Ahai-Chang, Chan Yu-Ru, Li Hui-Chun
Department of Microbiology and Immunology, School of Medicine, Tzu Chi University, Hualien 97004, Taiwan.
Department of Laboratory Medicine, Buddhist Tzu Chi General Hospital, Hualien 97004, Taiwan.
Pathogens. 2023 Jun 29;12(7):892. doi: 10.3390/pathogens12070892.
Ribonucleotide reductases (RRs or RNRs) catalyze the reduction of the OH group on the 2nd carbon of ribose, reducing four ribonucleotides (NTPs) to the corresponding deoxyribonucleotides (dNTPs) to promote DNA synthesis. Large DNA viruses, such as herpesviruses and poxviruses, could benefit their replication through increasing dNTPs via expression of viral RRs. Little is known regarding the relationship between cellular RRs and RNA viruses. Mammalian RRs contain two subunits of ribonucleotide reductase M1 polypeptide (RRM1) and two subunits of ribonucleotide reductase M2 polypeptide (RRM2). In this study, expression of cellular RRMs, including RRM1 and RRM2, is found to be down-regulated in hepatitis C virus (HCV)-infected Huh7.5 cells and Huh7 cells with HCV subgenomic RNAs (HCVr). As expected, the NTP/dNTP ratio is elevated in HCVr cells. Compared with that of the control Huh7 cells with sh-scramble, the NTP/dNTP ratio of the RRM-knockdown cells is elevated. Knockdown of RRM1 or RRM2 increases HCV replication in HCV replicon cells. Moreover, inhibitors to RRMs, including Didox, Trimidox and hydroxyurea, enhance HCV replication. Among various HCV viral proteins, the NS5A and/or NS3/4A proteins suppress the expression of RRMs. When these are taken together, the results suggest that HCV down-regulates the expression of RRMs in cultured cells to promote its replication.
核糖核苷酸还原酶（RRs或RNRs）催化核糖第2位碳原子上的羟基还原，将四种核糖核苷酸（NTPs）还原为相应的脱氧核糖核苷酸（dNTPs）以促进DNA合成。大型DNA病毒，如疱疹病毒和痘病毒，可通过表达病毒RRs增加dNTPs来促进其复制。关于细胞RRs与RNA病毒之间的关系，人们了解甚少。哺乳动物RRs包含两个核糖核苷酸还原酶M1多肽（RRM1）亚基和两个核糖核苷酸还原酶M2多肽（RRM2）亚基。在本研究中，发现细胞RRMs（包括RRM1和RRM2）的表达在丙型肝炎病毒（HCV）感染的Huh7.5细胞和含有HCV亚基因组RNA（HCVr）的Huh7细胞中下调。正如预期的那样，HCVr细胞中的NTP/dNTP比值升高。与带有sh-乱序对照的Huh7细胞相比，RRM敲低细胞的NTP/dNTP比值升高。敲低RRM1或RRM2可增加HCV复制子细胞中的HCV复制。此外，RRMs抑制剂，包括Didox、Trimidox和羟基脲，可增强HCV复制。在各种HCV病毒蛋白中，NS5A和/或NS3/4A蛋白抑制RRMs的表达。综合来看，这些结果表明HCV在培养细胞中下调RRMs的表达以促进其复制。
