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.
- Division of Translational Research, Kyoto Medical Center, National Hospital Organization, Kyoto, Japan.
- Clinical Research Institute, Kyoto Medical Center, National Hospital Organization, Kyoto, Japan.
- Department of Cardiovascular Medicine, Graduate School of Medicine, Kyoto University, Kyoto, Japan.
- 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.