Regulation of co-transcriptional pre-mRNA splicing by m6A through the low-complexity protein hnRNPG. Zhou KI, Shi H, et al.
N6-methyladenosine (m6A) modification occurs co-transcriptionally and impacts pre-mRNA processing, however the mechanism of co-transcriptional m6A-dependent alternative splicing regulation is still poorly understood. HnRNPG is an m6A reader protein that binds RNA through RRM and Arg-Gly- Gly (RGG) motifs. Here, we show that hnRNPG directly binds to the phosphorylated carboxy-terminal domain (CTD) of RNA polymerase II (RNAPII) using RGG motifs in its low-complexity region. Through interactions with the phosphorylated CTD and nascent RNA, hnRNPG associates co-transcriptionally with RNAPII and regulates alternative splicing transcriptome-wide. m6A near splice sites in nascent pre- mRNA modulate hnRNPG binding, which influences RNAPII occupancy patterns and promotes exon inclusion. Our results reveal an integrated mechanism of co-transcriptional m6A-mediated splicing regulation, in which an m6A reader protein uses RGG motifs to co-transcriptionally interact with both RNAPII and m6A-modified nascent pre-mRNA to modulate RNAPII occupancy and alternative splicing.