CARM1 Methylates MED12 to Regulate its RNA Binding Ability

The coactivator-associated arginine methyltransferase (CARM1) functions as a regulator for transcription, splicing and chromatin regulation by methylating a diverse array of substrates. In this study, we used CARM1 substrate antibodies to perform immunoprecipitation coupled with mass spectrometry (IP-MS) in MEFs and identified Mediator Subunit 12 (MED12) as a novel substrate for CARM1. ChIP-seq analysis using CARM1, MED12 and H3R17me2a (represents ‘CARM1 activity’) antibodies revealed that MED12 targeted by CARM1 is recruited to the EREs (estrogen-responsive elements). Additionally, RT-PCR studies showed that the MED12R1899K mutation disrupting the methylation site reduced the expression of ER-target genes. Thus, MED12 methylation targets it to ER-specific enhancers and positively modulates transcription of Estrogen-driven genes. ChIP-seq of CARM1, MED12 and H3R17me2a in MCF7 cells