Cyclin-dependent kinase-9 is a novel component of p300/GATA-4 complex required for hypertrophic responses in cardiac myocytes

Cyclin-dependent kinase-9 is a novel component of p300/GATA-4 complex required for hypertrophic responses in cardiac myocytes

Yoichi Sunagawa1, Tatsuya Morimoto2, Teruhisa Kawamura1, Tomohide Takaya1, Hiromichi Wada1, Akira Shimatsu1, Masatoshi Fujita3, Toru Kita2, Koji Hasegawa1.

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

第71回日本循環器学会学術集会 (神戸), 2007/03/15 (口演).

Abstract

A zinc finger protein GATA-4 is one of hypertrophy-responsive transcription factors, and increases its DNA-binding and transcriptional activities in response to hypertrophic stimuli in cardiac myocytes. Activation of GATA-4 during this process is mediated, in part, through acetylation by intrinsic histone acetyltransferases such as a transcriptional coactivator p300. Here, we show that cyclin-dependent kinase-9 (Cdk9), a component of positive transcription elongation factor b (P-TEFb) which increases activity of RNA Pol II by hyperphosphorylation, is a novel component of p300/GATA-4 complex. Immunoblotting analyses demonstrated that GATA-4 formed a complex with p300, Cdk9 and cyclin T1, another component of P-TEFb. A dominant-negative form of p300 disrupted the interaction of GATA-4 with Cdk9 or cyclin T1. Conversely, a dominant-negative form of Cdk9 and a Cdk9 kinase inhibitor, 5,6-dichloro-1-h-ribofuranosyl-benzimidazole (DRB) inhibited p300-induced acetylation of GATA-4-dependent transcription as well as acetylation of GATA-4. Stimulation of cardiac myocytes with phenylephrine (PE) increased the binding of GATA-4/p300 with Cdk9 or cyclin T1. DRB and a dominant-negative Cdk9 not only disrupted a complex of GATA-4/p300 with Cdk9 or cyclin T1, but also repressed PE-induced hypertrophic responses such as myofiber organization, increase in cell size in cardiac myocytes. These findings demonstrate that Cdk9 and cyclin T1 form a functional protein complex with GATA-4/p300 and that this large complex is required for hypertrophic responses in cardiac myocytes.