The myogenic protein MyoD requires two nuclear histone acetyltransferases,
CREB-binding protein (CBP)/p300 and PCAF, to transactivate muscle promoters
. MyoD is acetylated by PCAF in vitro, which seems to increase its affinity
for DNA We here show that MyoD is constitutively acetylated in muscle cell
s. In vitro, MyoD is acetylated both by CBP/p300 and by PCAF on two lysines
located at the boundary of the DNA binding domain. MyoD acetylation by CBP
/p300 (as well as by PCAF) increases its activity on a muscle-specific prom
oter, as assessed by microinjection experiments. MyoD mutants that cannot b
e acetylated in vitro are not activated in the functional assay, Our result
s provide direct evidence that MyoD acetylation functionally activates the
protein and show that both PCAF and CBP/p300 are candidate enzymes for MyoD
acetylation in vivo.