Abstract 15041: Protein Arginine Methyltransferase 5 and Methylosome Protein 50 Suppresses Hypertrophic Responses in Cardiomyocytes by Inhibition of p300/GATA4 Pathway
Introduction: One of the intrinsic histone acetyltransferases, p300, serves as a coactivator of hypertrophy-responsive transcriptional factors such as a cardiac zinc finger protein, GATA4, and is involved in its acetylation and DNA binding induced by hypertrophic stimuli. Disruption of the p300/GATA4 complex results in the inhibition of hypertrophic responses in cardiomyocytes. Protein arginine methylation caused by protein arginine methyltransferase 5 (PRMT5) plays a critical role in differential gene expression through modulating protein-protein and protein-DNA/RNA interactions. Methylosome protein 50 (MEP50) is a component of the PRMT5 complex and an activator of PRMT5. By tandem affinity purification and mass spectrometric analyses, we identified PRMT5 and MEP50 as novel GATA4-binding partners. However, the precise functional relationships among p300/GATA4, PRMT5, and MEP50 remain unknown.
Methods and Results: First, to examine the binding of PRMT5 and MEP50 to GATA4 and p300, expression plasmids encoding these proteins were used to co-transfect into HEK293 cells. Nuclear extracts from these cells were subjected to immunoprecipitation, followed by Western-blot analysis. PRMT5 and MEP50 formed a complex not only with GATA4 but also with p300 in these cells. The overexpression of PRMT5 inhibited p300-induced GATA4-dependent activities of the atrial natriuretic factor (ANF) and endothelin-1 (ET-1) promoters as well as the acetylation of GATA-4. Conversely, the knockdown of PRMT5 by RNAi enhanced these promoter activities in HEK293 cells. Moreover, PRMT5 increased the methylation of p300 in these cells. Finally, overexpression of PRMT5 or MEP50 in cardiomyocytes inhibited PE-induced hypertrophic responses such as myofibrillar organization, an increase in the cell size, and activation of the ANF and ET-1 promoters.
Conclusions: PRMT5 and MEP50 form a functional protein complex with p300/GATA4. PRMT5 and MEP50 inhibit p300/GATA4-dependent transcription and hypertrophic responses in cardiomyocytes, in part, through the methylation of p300.
- © 2011 by American Heart Association, Inc.