c-Myb acetylation at the carboxyl-terminal conserved domain by transcriptional co-activator p300

Transcription factor c-Myb plays important roles in cell survival and diffe rentiation in immature hematopoietic cells, Here we demonstrate that c-Myb is acetylated at the carboxyl-terminal conserved domain by histone acetyltr ansferase p300 both in vitro and in vivo. The acetylation sites in Pho have been located at the lysine residues of the conserved domain (K471, K480, K 485) by the use of the mutant Myb (Myb-KAmut), in which all three lysine re sidues are substituted into alanine. Electrophoretic mobility shift assay r eveals that Myb-KAmut shows higher DNA binding activity than wild type c-My b and that acetylation of c-Myb in vitro by p300 causes dramatic increase i n DNA binding activity, Accordingly, transactivation activity of both mim-1 and CD34 promoters by Myb-KAmut is higher than that driven by wild type c- Myb. Furthermore, the bromodomain of p300, in addition to the histone acety ltransferase (HAT) domain, is required for effective acetylation of Myb, an d hGCN5 is revealed to be a factor acetyltransferase for c-Myb in vitro. We present a new manner of post-translational modification of the c-Myb prote in and the potential significance of the acetylation in c-Myb.