CREB-binding protein acetylates hematopoietic transcription factor GATA-1 at functionally important sites

The transcription factor GATA-1 is a key regulator of erythroid-cell differ entiation and survival. We have previously shown that the transcriptional c ofactor CREB-binding protein (CBP) binds to the zinc finger domain of GATA- 1, markedly stimulates the transcriptional activity of GATA-1, and is requi red for erythroid differentiation. Here we report that CBP, but not p/CAF, acetylates GATA-1 at two highly conserved lysine-rich motifs present at the C-terminal tails of both zinc fingers. Using [H-3]acetate labelling experi ments and anti-acetyl lysine immunoprecipitations, we shaw that GATA-1 is a cetylated in vivo at the same sites acetylated by CBP in vitro. In addition , we show that CBP stimulates GATA-1 acetylation in vivo in an E1A-sensitiv e manner, thus establishing a correlation between acetylation and transcrip tional activity of GATA-1. Acetylation in vitro did not alter the ability o f GATA-1 to bind DNA, and mutations in either motif did not affect DNA bind ing of GATA-1 expressed in mammalian cells. Since certain functions of GATA -1 are revealed only in an erythroid environment, GATA-1 constructs were ex amined for their ability to trigger terminal differentiation when introduce d into a GATA-1-deficient erythroid cell line. We found that mutations in e ither acetylation motif partially impaired the ability of GATA-1 to induce differentiation while mutations in both moths abrogated it completely. Take n together, these data indicate that CBP is an important cofactor for GATA- 1 and suggest a novel mechanism in which acetylation by CEP regulates GATA- 1 activity in erythroid cells.