The kinase activity of Cdk9 is required for phosphorylation of p300 and acetylation of GATA4 as well as cardiomyocyte hypertrophy

The kinase activity of Cdk9 is required for phosphorylation of p300 and acetylation of GATA4 as well as cardiomyocyte hypertrophy

Yoichi Sunagawa1, Tatsuya Morimoto1, Tomohide Takaya1, Teruhisa Kawamura1, Hiromichi Wada1, Akira Shimatsu1, Masatoshi Fujita2, Toru Kita2, Koji Hasegawa1.

  1. Kyoto Medical Center, National Hospital Organization, Kyoto, Japan.
  2. Graduate School of Medicine, Kyoto University, Kyoto, Japan.

第12回日本心不全学会学術集会 (東京), 2008/10/17 (ポスター).

Abstract

A zinc finger protein GATA-4 is one of the factors involved in transcriptional regulation during myocardial cell hypertrophy. In response to hypertrophic stimuli, GATA-4 forms a complex with an intrinsic histone acetyltransferase (HAT), p300, and increases its transcriptional activity by acetylation. By tandem affinity purification and mass spectrometric analyses, we identified cyclin-dependent kinase-9 (Cdk9), a component of positive transcription elongation factor b (P-TEFb), as a novel GATA4-binding partner. Cdk9 also forms a complex with p300 as well as GATA-4. However, precise functional relationship between p300/GATA-4 and P-TEFb is unknown. Intact p300 induced not only the acetylation of GATA-4 but also the interaction of GATA-4 with P-TEFb. Furthermore, p300 induced the hyperphosphorylation of RNA Pol II, suggesting that p300 is involved in regulating the kinase activity of Cdk9. All of these effects were inhibited by a dominant-negative form of (DN-) p300. Meanwhile, DN-Cdk9, which loses its kinase activity by a single amino acid substitution, inhibited p300-induced hyperphophorylation of RNA Pol II. Notably, DN-Cdk9 inhibited phosphorylation of p300 as well as p300-induced acetylation and DNA binding of GATA-4, indicating a requirement of Cdk9 in the HAT activity of p300. Finally, both DN-p300 and DN-Cdk9 inhibited phenylephrine-induced hypertrophic responses in cardiac myocytes. These findings demonstrate that Cdk9 forms a functional complex with the p300/GATA4 and is required for p300/GATA4-transcriptional pathway during cardiomyocyte hypertrophy.