In the absence of H2A.Z, the SWR1 histone replacement complex causes genetic instability, stress and genome transcription misregulation

The SWR1 complex replaces the canonical histone H2A with the variant H2A.Z (Htz1 in yeast) at specific chromatin regions. This dynamic alteration in nucleosome structure provides a molecular mechanism to regulate transcription. Here we analysed the transcription profiles of single and double mutants and wild-type cells by whole-genome microarray analysis. Our results indicate that genome-wide transcriptional misregulation in htz1 can be partially or totally suppressed if SWR1 is not formed (swr1), if it forms but cannot bind to chromatin (swc2), or if it binds to chromatin but has no histone replacement activity (swc5). These results suggest that in htz1 the nucleosome remodelling activity of SWR1 affects chromatin integrity because of an attempt to replace H2A with Htz1 in the absence of the latter.

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Morillo-Huesca M, Clemente-Ruiz M, Andújar E, Prado F