The 400 kDa subunit of the PCAF histone acetylase complex belongs to the ATM superfamily

PCAF histone acetylase is found in a complex with more than 20 associated p olypeptides. Here we report cloning and characterization of the 400 kDa PCA F-associated factor referred to as PAF400. PAF400 is almost identical to TR RAP, which binds to c-Myc and E2F, and has significant sequence similaritie s to the ATM superfamily including FRAP, ATM, ATR, and the catalytic subuni t of DNA-PK. Remarkably, PAF400 and FRAP share sequence similarity in broad regions that cover 80% of the entire PAF400 sequence. However, unlike the other members of the ATM superfamily, PAF400 is not: a protein kinase as ju dged from the lack of kinase motif and autophosphorylation activity. We dis cuss the possibility that PAF400 may play a role in signaling of DNA damage to p53 by stimulation of p53 acetylation.