Integrated analysis of H2A.Z isoforms reveals a complex interplay in gene regulation [ChIP-seq]

The H2A.Z histone variant plays major roles in the control of gene expression. In human, H2A.Z is encoded by two genes expressing two isoforms, H2A.Z.1 and H2A.Z.2 differing by three amino acids. Here, we undertook an integrated analysis of the independent and interdependent functions of these two isoforms in gene expression using endogenously-tagged isoform. RNA-Seq analysis following depletion of either isoform or both together in untransformed cells showed that they can regulate both distinct and overlapping sets of genes positively or negatively in a context-dependent manner. Our data revealed that the two isoforms have similar or antagonistic function depending on the gene. H2A.Z.1 and H2A.Z.2 can replace each other at Transcription Start Sites, providing a molecular explanation for this interplay. Mass spectrometry analysis showed that H2A.Z.1 and H2A.Z.2 have specific interactors, PHF14 and associated proteins for H2A.Z.1 and the histone deacetylase SIRT1 for H2A.Z.2. Moreover, we show that PHF14 and SIRT1 mediate the functional antagonism between H2A.Z.1 and H2A.Z.2. In conclusion, we propose a model in which the balance between H2A.Z.1 and H2A.Z.2 at promoters is critically important to regulate specific gene expression and depends on the recruitment of specific proteins. Our work thus provides an additional layer of complexity to the control of gene expression by histone variants. H2A.Z1 and H2A.Z2 ChIP-seq datasets in U2OS Flag-Z1 and U2OS Flag-Z2 cells.