Regulation of Co-transcriptional Pre-mRNA Splicing by m6A through the Low-Complexity Protein hnRNPG

• DOI: 10.1016/j.molcel.2019.07.005
• Publication Date: 2019-08-21T14:27:46Z
• Authors: Katherine I. Zhou; Hailing Shi; Ruitu Lyu; Adam C. Wylder; Żaneta Matuszek; Jessica N. Pan; Chuan He; Marc Parisien; Tao Pan
• Keywords: 0301 basic medicine; Adenosine; Binding Sites; Transcription, Genetic; Amino Acid Motifs; Exons; Heterogeneous-Nuclear Ribonucleoproteins; Alternative Splicing; Structure-Activity Relationship; 03 medical and health sciences; HEK293 Cells; RNA Precursors; Humans; RNA Polymerase II; RNA, Messenger; Protein Binding

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. Heterogeneous nuclear ribonucleoprotein G (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 modulates 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.