CELL BIOLOGY:
Clinging to Histones
Michael Hagmann
Structural biologists have taken a close look at a protein region, or "domain," that may guide proteins to specific sites on chromatin, the complex of DNA and proteins making up the chromosomes. The region in question is the bromodomain, a conserved sequence containing roughly 100 amino acids found in some 30 chromatin-associated proteins. Using nuclear magnetic resonance, the researchers have determined the structure of the bromodomain and shown that it contains a cleft that specifically recognizes acetylated histones. Because acetyl addition to histones helps open up the chromatin so gene expression can occur, the finding suggests that the bromodomain helps bring in the proteins necessary for gene activation.