H2A.Z is required for global chromatin integrity and for recruitment of RNA polymerase II under specific conditions

Evolutionarily conserved variant histone H2A.Z has been recently shown to r egulate gene transcription in Saccharomyces cereviside. Here we show that l oss of H2A.Z in this organism negatively affects the induction of GAL genes . Importantly, fusion of the H2A.Z C-terminal region to S phase H2A without its corresponding C-terminal region can mediate the variant histone's spec ialized function in GAL1-10 gene induction, and it restores the slow-growth phenotype of cells with a deletion of HTZ1. Furthermore, we show that the C-terminal region of R2A.Z can interact with some components of the transcr iptional apparatus. In cells lacking H2A.Z, recruitment of RNA polymerase I I and TATA-binding protein to the GAL1-10 promoters is significantly dimini shed under inducing conditions. Unexpectedly, we also find that H2A.Z is re quired to globally maintain chromatin integrity under GAL gene-inducing con ditions. We hypothesize that H2A.Z can positively regulate gene transcripti on, at least in part, by modulating interactions with RNA polymerase II-ass ociated factors at certain genes under specific cell growth conditions.