N6-methyladenosine (m6A) is the most abundant internal RNA modification of cellular mRNAs. m6A is recognised by YTH domain-containing proteins, which selectively bind to m6A-decorated RNAs regulating their turnover and translation. Using an m6A-modified hairpin present in the Kaposi’s sarcoma associated herpesvirus (KSHV) ORF50 RNA, we identified seven members from the ‘Royal family’ as putative m6A readers, including SND1. RIP-seq and eCLIP analysis characterised the SND1 binding profile transcriptome-wide, revealing SND1 as an m6A reader. We further demonstrate that the m6A modification of the ORF50 RNA is critical for SND1 binding, which in turn stabilises the ORF50 transcript. Importantly, SND1 depletion leads to inhibition of KSHV early gene expression showing that SND1 is essential for KSHV lytic replication. This work demonstrates that members of the ‘Royal family’ have m6A-reading ability, greatly increasing their epigenetic functions beyond protein methylation.

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. Kaposi 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 NFκB signalling. Overall, this work highlights the central importance of m6A in modulating cellular gene expression to influence viral infection.

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. Kaposi’s sarcoma-associated herpesvirus (KSHV) reactivation from the latent phase leads to the 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. Our 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 NFκB signalling. Overall, this work highlights the central importance of m6A in modulating cellular gene expression to influence viral infection.

No abstract

We previously showed that the germ cell specific nuclear protein RBMXL2 represses cryptic splicing patterns during meiosis and is required for male fertility. RBMXL2 evolved from the X-linked RBMX gene, which is silenced during meiosis due to sex chromosome inactivation. It has been unknown whether RBMXL2 provides a direct replacement for RBMX in meiosis, or whether RBMXL2 evolved to deal with the transcriptionally permissive environment of meiosis. Here we find that RBMX primarily operates as a splicing repressor in somatic cells, and specifically regulates a distinct class of exons that exceed the median human exon size. RBMX protein-RNA interactions are enriched within ultra-long exons, particularly within genes involved in genome stability, and repress the selection of cryptic splice sites that would compromise gene function. These similarities in overall function suggested that RBMXL2 might replace the function of RBMX during meiosis. To test this prediction we carried out inducible expression of RBMXL2 and the more distantly related RBMY protein in somatic cells, finding each could rescue aberrant patterns of RNA processing in response to RBMX depletion. The C-terminal disordered domain of RBMXL2 is sufficient to rescue proper splicing control after RBMX depletion. Our data indicate that RBMX and RBMXL2 have parallel roles in somatic tissues and the germline that must have have been conserved over at least 200 million years of mammalian evolution. We propose RBMX family proteins are particularly important for the splicing inclusion of ultra-long exons because these would be particularly susceptible to disruption by cryptic splice site selection.