The 5-methylcytosine modification in the PB2 cRNA of influenza virus impairs viral RNA replication and attenuates pathogenicity

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 PB2 complementary RNA (cRNA) enhances its transcription and slows its degradation rate, 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.