RbAp48/46 are novel components of p300/GATA4 comprex required for hypertrophic responses in cardiac myocytes

RbAp48/46 are novel components of p300/GATA4 comprex required for hypertrophic responses in cardiac myocytes

Taishi Terada1, Yoichi Sunagawa1,2,4, Yasufumi Katanasaka1, Hiromichi Wada4, Tomohide Takaya3,4, Akira Shimatsu4, Takeshi Kimura3, Masatoshi Fujita2, Koji Hasegawa4, Tatsuya Morimoto1.

  1. Division of Molecular Medicine, School of Pharmaceutical Sciences, University of Shizuoka, Shizuoka, Japan.
  2. Department of Human Health Sciences, Graduate School of Medicine, Kyoto University, Kyoto, Japan.
  3. Department of Cardiovascular Medicine, Graduate School of Medicine, Kyoto University, Kyoto, Japan.
  4. Division of Translational Research, Kyoto Medical Center, National Hospital Organization, Kyoto, Japan.

第14回日本心不全学会学術集会 (東京), 2010/10/07 (ポスター).

Abstract

Introduction: A zinc finger protein GATA4 is one of the hypertrophy-responsive transcription factors, and increases its DNA-binding and transcriptional activities in response to hypertrophic stimuli in cardiac myocytes. By tandem affinity purification and mass spectrometric analyses, we identified that retinoblastoma binding proteins, RbAp46 and RbAp48, components of the nucleosome remodeling and histone deacetylase (NuRD) complex which regulates chromatin remodeling, are novel components of p300/GATA4 complex. However, precise functional relationship between p300/GATA4 and RbAp46 and RbAp48 are unknown.

Methods and Results: GST pull-down assays revealed that the C-terminals of RbAp46 and RbAp48 bound to the N-terminal of GATA4 and C/H-3 domain of p300, respectively. Immunoprecipitation followed by Western blotting demonstrated that intact p300 induced the acetylation of GATA4. Furthermore, p300 induced the GATA4-dependent cardiac hypertrophy response gene expression. All of these effects were inhibited by co-expression of RbAp46 and RbAp48. Moreover, overexpression of RbAp46 or RbAp48 inhibited phenylephrine-induced hypertrophic response gene promoter activity and cell surface area in cardiomyocytes. Finally, an HDAC inhibitor, trichostatin A, could rescue RbAp46- and RbAp48-induced decrease in p300/GATA4-dependent transcription.

Conclusions: These findings demonstrate that RbAp46 and RbAp48 suppressed the p300 HAT activity during cardiomyocyte hypertrophy. These inhibitory effects are not dependent on HDACs. Further examinations are needed to clarify the precise mechanisms of inhibitory effects of RbAp46 and RbAp48 on cardiac hypertrophy.