m6A regulates the stability of cellular transcripts required for efficient KSHV lytic replication

The epitranscriptomic modification N6-methyladenosine (m6A) is a ubiquitous feature of the mammalian transcriptome. It modulates mRNA fate and dynamics to exert regulatory control over numerous cellular processes and disease pathways, including viral infection. Kaposis sarcoma-associated herpesvirus (KSHV) reactivation from the latent phase leads to redistribution of m6A topology upon both viral and cellular mRNAs within infected cells. Here we investigate the role of m6A in cellular transcripts upregulated during KSHV lytic replication. Results show that m6A is crucial for the stability of the GPRC5A mRNA, whose expression is induced by the KSHV latent-lytic switch master regulator, the replication and transcription activator (RTA) protein. Moreover, we demonstrate that GPRC5A is essential for efficient KSHV lytic replication by directly regulating NF{kappa}B signalling. Overall, this work highlights the central importance of m6A in modulating cellular gene expression to influence viral infection. Author SummaryChemical modifications on mRNA, such as m6A, are functionally linked to all stages of mRNA metabolism and regulate a variety of biological processes. As such, m6A modification offers unique possibilities for viruses to modulate both viral and host gene expression. m6A has been identified on transcripts encoded by a wide range of viruses and studies to investigate m6A function have highlighted distinct roles in virus life cycles. In addition, cellular transcripts undergoing differential m6A status during infection may also be important for virus replication. In this study we investigate the impact of differential m6A modification in host transcripts during KSHV lytic replication, by identifying transcripts with altered methylation profiles between latent and lytic replication programmes. We show that increased m6A content in one of these cellular mRNAs, GPRC5A, enhances its stability and correlates with increased abundance during KSHV lytic replication. Moreover, the importance of GPRC5A is demonstrated by depletion studies, showing that GPRC5A enhances KSHV lytic replication by inhibiting cell signalling pathways.