Protein Arginine Methyltransferase 6 Controls Cardiac Hypertrophy by Differential Arginine and Lysine Methylation of Histone H3

Heart failure remains a common cause of hospitalization and death worldwide. Heart failure can be caused by dysregulation of gene expression following abnormal expression of histone modifying enzymes. While lysine acetylation and methylation of histones have been the topic of many investigations, the role of arginine methylation in H3 has been overlooked. In an effort to understand regulatory mechanisms implicated in cardiac hypertrophy and heart failure, we assessed protein arginine methyl transferase (PRMT) members in the left ventricle of failing human hearts and control hearts. Our results show a specific up-regulation of PRMT6 mRNA in failing human hearts (5.95±2.16 fold in failing versus control, p=0.003) which also occurs in the compensatory phase of cardiac hypertrophy in mouse hearts subjected to pressure overload hypertrophy, and in neonatal rat ventricular myocytes (NRVM) stimulated with the hypertrophic agonist phenylephrine (PE). These changes are associated with a significant increase in arginine 2 asymmetric methylation of H3 (H3R2me2a) and reduced lysine 3 tri-methylation of H3 (H3K4me3) both in NRVM and in vivo . Importantly, forced expression of PRMT6 in NRVM stimulated with PE, enhances the expression of atrial natriuretic peptide (ANP). Conversely, silencing of PRMT6 reduces ANP protein expression and cell size, indicating that PRMT6 is critical for PE-mediated cardiac hypertrophy of NRVM. Also, silencing of PRMT6 reduces H3R2me2a, a mark associated with transcriptional repression. To evaluate the role of PRMT6 on cardiac contractility and global ion channel activity, we assessed contractility and global field potentials in live NRVM expressing normal and low level PRMT6 using the RTCA CardioECR system (ACEA Bioscience Inc.). Strikingly, reduced expression of PRMT6 drastically inhibits the contraction rate of NRVM, which is paralleled by a slight increase in the QT interval. All together, our results indicate that PRMT6 is a critical regulator of cardiac hypertrophy, implicating H3R2me2a as an important histone modification. Future studies investigating the specific gene programs regulated by PRMT6 are on their way. This study may help identify novel points of control to design new drugs for the treatment of heart failure.