Genes Dev. doi:10.1101/gad.1787109 (2009)

DNA winds around bundles of proteins called histones to make nucleosomes. The histone H2A.Z — a variant of H2A — was thought to prepare genes for activation and then exit the scene once this had occurred. But Luc Gaudreau of the University of Sherbrooke in Canada and his co-workers now show that it is recruited only to the promoter regions of certain genes — those regulated by oestrogen receptor alpha — at around the time of induction. Moreover, recruitment recurs in a cyclical manner, boosting gene expression.

By identifying proteins that bind to specific DNA sequences, the researchers studied the timing of H2A.Z recruitment to a gene promoter after cells were exposed to oestradiol. Compared with H2A, H2A.Z triggers a shift in nucleosome position and stabilizes the binding of other proteins that promote gene expression.