Arginine methylation regulates widespread alternative polyadenylation

Alternative polyadenylation (APA) has recently been recognized as a universal mechanism for gene regulation, but it remains unclear how APA is controlled. Here we report that the Arabidopsis thaliana Protein Arginine Methyltransferase 10 (AtPRMT10) regulates global APA with its protein partner HLP1, a conserved hnRNP A/B protein. HLP1 binds preferentially to A-rich and U-rich cis-elements around polyadenylation sites, thereby linking AtPRMT10 to the control of APA through protein-protein interactions. AtPRMT10 mutations cause significant proximal-to-distal poly(A) site shifts largely overlapping with those in hlp1-1 mutants. Proximal polyadenylation is maintained by AtPRMT10-directed methylation and is mediated in part by methylation of HLP1 at specific arginine residues. Our findings demonstrate that arginine methylation of an RNA-binding protein adds a novel layer of regulation to widespread alternative polyadenylation. Overall design: Investigate the role of PRMT10 in alternative polyadenylation.