Cyclin-dependent kinase-9 is required for histone acetyltransferase activity of p300

Cyclin-dependent kinase-9 is required for histone acetyltransferase activity of p300

Yoichi Sunagawa1, Tatsuya Morimoto1, Teruhisa Kawamura1, Tomohide Takaya1, Hiromichi Wada1, Akira Shimatsu2, Masatoshi Fujita4, Toru Kita3, Koji Hasegawa1.

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

第72回日本循環器学会学術集会 (福岡), 2008/03/29 (口演).

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. We have shown that cyclin-dependent kinase-9 (Cdk9), a component of positive transcription elongation factor b (P-TEFb), is a novel GATA-4-binding partner. Cdk9 and cyclin T1, another component of P-TEFb, form 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 hyperphosphorylation of RNA Pol II. Notably, DN-Cdk9 inhibited p300-induced acetylation 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 components of a large complex containing p300/GATA-4 and P-TEFb positively regulate each other and are required for hypertrophic responses in cardiac myocytes.