retardation and other abnormalities [20]. CBP and p300 are distinct proteins but often referred to interchangeably due to their high degree of similarity. CBP/p300 can acetylate H2A, H2B, H3, and H4 and are recruited to specific genes through their interactions with several transcription factors (e.g. CREB, Fos/Jun). Importantly, each of these classes of HATs can acetylate non-histone proteins as well, which is known to play an important role in a variety of cell signaling pathways [36]. Interestingly, several transcription factors, such as Clock, have been reported to possess HAT activity themselves. Studies are underway to determine the contribution of such acetylation to the regulation of gene activity [37, 38].
