Abstract 12112: Genome-Wide Binding Profiles of c-Myc and RNA-Polymerase II Clarifies c-Myc-Mediated Circuit Pathway in RNA Metabolism in Cardiomyocytes
Background:c-Myc (Myc) transcription factor is rapidly induced in cardiomyocyte under adrenergic stimulation and has a functional property to strongly induce cardiomyocyte hypertrophy. Although the underlying mechanisms of pro-hypertrophic effect of Myc including the induction of protein and DNA synthesis have been extensively studied, the functional role for Myc in RNA metabolism in cardiomyocytes remains unclear.
Methods:Global RNA production in rat neonatal cardiomyocytes with or without increasing amount of Myc protein were evaluated using 5-Ethynyl Uridine (EU) incorporation. Quantitative analysis using imaging cytometry demonstrated that adenoviraly transduced Myc significantly increased the amount of global RNA production in cardiomyocytes. To clarify the direct effect of Myc for mRNA transcription, we performed chromatin immunoprecipitation followed by high-throughput sequencing (ChIP-seq) in replicates and obtained genome-wide binding profiles of Myc and RNA-polymerase II (Pol II) in cardiomyocytes before and after transduction. We established the algorithm to quantify the Pol II enrichment and found that transduced Myc induced global Pol II recruitment both at promoter region and gene body.
Results:A total of 3108 genes were identified as directly Myc-bound genes. However, intriguingly, at more than half of the Myc-bound genes, Pol II occupancy did not change before and after transduction. We identified 946 Myc-bound genes with significant Pol II recruitment and functional enrichment analysis clarified that these genes were significantly involved in ribosomal biogenesis and RNA processing. Among these genes we identified previously undetermined direct Myc target gene which was immediately induced both in cardiomyocytes after adrenergic stimulation and in heart tissues after pressure-overload. This Myc target gene turned out conversely to be a negative regulator of cardiomyocyte hypertrophy via affecting RNA degradation pathway.
Conclusions:Genome-wide analysis of Myc and Pol II binding clarifies Myc mediated circuit pathway in RNA metabolism in cardiomyocytes. These findings provide a new insight into pathological relevance of RNA metabolism in hypertrophic response in cardiomyocytes.
Author Disclosures: Y. Masumura: None.
- © 2014 by American Heart Association, Inc.