Figure 7.

Role of H2A.Z in the Regulation of Gene Activity in Arabidopsis.

Some genes require H2A.Z in TSS to maintain their transcriptional activity (left panel). These genes stay hypoactive in the arp6 mutant. As the arp6 mutant exhibits some residual evenly distributed H2A.Z, it is difficult to speculate how general this mechanism is. On the other hand, H2A.Z across the whole gene length adopts a repressive role in transcription in most genes that change their expression under stress conditions (right panel). These genes stay hyperactive in the arp6 mutant. We hypothesize that the biological role of H2A.Z-repressive influence on transcription is to counteract unwanted expression under noninductive conditions. H2A.Z is partially removed from nucleosomes during transcriptional activation. The model assumes that in +1 nucleosomes, H2A.Z may adopt both a promoting and repressive role, depending on additional factors such as nucleosome composition or histone modifications.