Interaction between Acetylated MyoD and the Bromodomain of CBP and/or p300

Abstract

Acetylation is emerging as a posttranslational modification of nuclear proteins that is essential to the regulation of transcription and that modifies transcription factor affinity for binding sites on DNA, stability, and/or nuclear localization. Here, we present both in vitro and in vivo evidence that acetylation increases the affinity of myogenic factor MyoD for acetyltransferases CBP and p300. In myogenic cells, the fraction of endogenous MyoD that is acetylated was found associated with CBP or p300. In vitro, the interaction between MyoD and CBP was more resistant to high salt concentrations and was detected with lower doses of MyoD when MyoD was acetylated. Interestingly, an analysis of CBP mutants revealed that the interaction with acetylated MyoD involves the bromodomain of CBP. In live cells, MyoD mutants that cannot be acetylated did not associate with CBP or p300 and were strongly impaired in their ability to cooperate with CBP for transcriptional activation of a muscle creatine kinase-luciferase construct. Taken together, our data suggest a new mechanism for activation of protein function by acetylation and demonstrate for the first time an acetylation-dependent interaction between the bromodomain of CBP and a nonhistone protein.

ACKNOWLEDGMENTS

This work was supported by grants from the Association pour la Recherche sur le Cancer and from the Association Française contre les Myopathies to A.H.-B. and from the European 5th PCRDT (grant QLRT 1999-00866) to A.H.-B. A.P. was awarded a fellowship from the Federation of European Biochemical Societies (FEBS).

We thank L. Cabanie for the preparation of recombinant proteins, V. Ogryzko, K. Breitschopf, A. Ciechanover, W. Lee Kraus, and S. A. Leibovitch for the kind gift of reagents, and L. L. Pritchard for helpful discussions and critical reading of the manuscript.