Solution structures of the N-terminal domain of histone H4

Histones, nuclear proteins that interact with DNA to form nucleosomes, are essential for both the regulation of transcription and the packaging of DNA within chromosomes. The N-terminal domain of histone H4 contains four acetylation sites at lysine residues and may play a separate role in chromatin structure from the remainder of the H4 chain. We performed circular dichroism and NMR characterization of both native (H4(NTP)) and acetylated (Ace-H4(NTP)) peptides containing N-terminal acetylation domain of histone H4 for various pH environments. Data from CD and NMR suggested that H4 NTP exhibited a pH-dependent conformational change, whereas the Ace-H4(NTP) is insensitive to pH change. However, both peptides showed a defined structural form at acidic pH environments. The solution structure for Ace-H4(NTP) shows two structurally independent regions comprising residues of Leu(10)-Gly(13) and Arg(19)-Leu(22), demonstrating relatively well-defined turn-type structures. Our results suggest that N-terminal acetylated region of H4 prefers an extended backbone conformation at neutral pH, however, upon acetylation, the regions containing lysine residues induce structural transition, having defined structural form for its optimum function.