De novo assembly of RNA mA modification factors into viral genome-associated nuclear bodies drives HCMV RNA accumulation.

The factors that install and recognize N-methyladenosine (mA) on RNA to regulate gene expression are well characterized, but how their spatial organization responds to physiological stress, including infection, is unclear. Here, we show that human cytomegalovirus (HCMV) infection induces accumulation of mA methyltransferase subunits, including WTAP, together with nuclear mA reader YTHDC1, into distinctive, membraneless nuclear bodies (NBs) overlapping with incoming virus genomes and immediate-early (IE) RNA transcripts. De novo assembly and integrity of these DNA-associated, IE, virus-activated NBs requires RNAPII transcription, METTL3 mA methyltransferase activity, and mA recognition by YTHDC1, but not new protein synthesis. Depleting YTHDC1 or WTAP limits the accumulation of critical HCMV RNAs required for virus DNA replication, interfering with virus reproduction. This reveals a surprising strategy whereby a discrete sub-nuclear RNA biogenesis compartment replete with RNAPII and mA modification components is swiftly consolidated in proximity to infecting HCMV genomes to initialize and sustain virus gene expression.