The 5-methylcytosine methylation in PB2 gene of influenza virus interferes viral RNA replication and pathogenicity

As a pivotal epigenetic modification, 5-methylcytosine (m5C) plays significant roles in RNA stability, translation regulation, and cellular metabolism. Growing evidence suggests that m5C methylation is involved in the regulation of virus-host interactions. However, its function during influenza virus infections remains elusive. Here, we demonstrate for the first time that m5C methylation of the influenza virus PB2 gene, encoding a core polymerase subunit, acts as a negative regulator of viral infection. Loss of m5C modification in complementary PB2 RNA enhances its transcription and translation efficiency, facilitates polymerase binding to RNA, and promotes viral genomic RNA synthesis. The subsequent accumulation of RNA and polymerase proteins accelerates the nuclear export of viral ribonucleoprotein complexes, enhances progeny virion assembly and maturation, and ultimately leads to enhanced viral pathogenicity. Our findings reveal a novel mechanism by which m5C methylation fine-tunes influenza virus replication by suppressing viral RNA synthesis, and provide evidence for a previously unrecognized innate antiviral strategy centered on m5C-mediated epitranscriptomic regulation.

作为一种关键的表观遗传修饰，5-甲基胞嘧啶（5-methylcytosine，简称m5C）在RNA稳定性、翻译调控以及细胞代谢中发挥着重要作用。越来越多的研究证据表明，m5C甲基化参与调控病毒与宿主的相互作用。然而，其在流感病毒感染过程中的功能仍不甚明晰。本研究首次证实，编码核心聚合酶亚基的流感病毒PB2基因的m5C甲基化，可作为病毒感染的负调控因子。互补PB2 RNA的m5C修饰缺失，可增强其转录与翻译效率，促进聚合酶与RNA的结合，并加速病毒基因组RNA的合成。后续RNA与聚合酶蛋白的积累，会加速病毒核糖核蛋白复合物的核输出，提升子代病毒粒子的组装与成熟效率，最终增强病毒的致病力。本研究揭示了一种全新的调控机制：m5C甲基化通过抑制病毒RNA合成来微调流感病毒的复制过程，并为一种此前未被发现的、以m5C介导的表观转录组调控为核心的天然抗病毒策略提供了实验证据。