Increased affinity of c-Myb for CREB-binding protein (CBP) after CBP-induced acetylation.
The c-myb proto-oncogene product (c-Myb) is a sequence-specific DNA-binding protein that functions as a transcriptional activator. The transcriptional coactivator CREB-binding protein (CBP) binds via its KIX domain to the activation domain of c-Myb and mediates c-Myb-dependent transcriptional activation. CBP possesses intrinsic histone acetyltransferase activity, and can acetylate not only histones but also certain transcriptional factors such as GATA1 and p53. Here we demonstrate that the C/H2 domain of CBP, which is critical for the acetyltransferase activity, also directly interacts with the negative regulatory domain (NRD) of c-Myb. Consistent with this observation, CBP acetylated c-Myb in vitro at Lys(438) and Lys(441) within the NRD. In addition, CBP acetylated c-Myb in vivo not only at the sites found in this study but also at the p300-induced acetylation sites reported recently. Replacement of lysine by arginine at all of these sites dramatically decreased the trans-activating capacity of c-Myb. The results of transcriptional activation assays with c-Myb acetylation site mutants suggested that acetylation of c-Myb at each of these five sites synergistically enhances c-Myb activity. Mutations of these acetylation sites reduced the strength of the interaction between c-Myb and CBP. Thus, acetylation of c-Myb by CBP increases the trans-activating capacity of c-Myb by enhancing its association with CBP. These results demonstrate a novel molecular mechanism of regulation of c-Myb activity.
Sano
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Laborartory of Molecular Genetics, RIKEN Tsukuba Institute and the CREST (Core Research for Evolutional Science and Technology) Research Project of JST (Japan Science and Technology Corporation), 3-1-1 Koyadai, Tsukuba, Ibaraki 305-0074, Japan.
Ishii
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S
D000107:Acetylation; D020816:Amino Acid Motifs; D050882:CREB-Binding Protein; D006801:Humans; D008239:Lysine / Q000378:metabolism; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D000090063:Proto-Oncogene Mas; D020598:Proto-Oncogene Proteins c-myb / Q000235:genetics / Q000378:metabolism*; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation / Q000502:physiology*; D014162:Transfection; D014407:Tumor Cells, Cultured
C000715470:MAS1 protein, human; D009687:Nuclear Proteins; D000090063:Proto-Oncogene Mas; D020598:Proto-Oncogene Proteins c-myb; D015534:Trans-Activators; D050882:CREB-Binding Protein; C494363:CREBBP protein, human; D008239:Lysine