Figure 4.

Working models for the NuA4-dependent activation of the flowering time master regulators FLC and FT. (A) H2A.Z deposition mediated by SWR1 and histone H4 and H2A.Z acetylation performed by the putative NuA4 catalytic subunits HAM1/2 in genomic regions surrounding FLC TSS are required for FLC expression. FRI-C, together with HAM1 and a plethora of chromatin remodelers and transcriptional regulators assist in the recruitment of SWR1 to FLC chromatin, fine tuning FLC expression by facilitating the incorporation of H2A.Z and histone PTMs. (B) HAM1/2 mediate H4K5 acetylation at FT chromatin promoting its transcriptional activation. HAM1/2 interact with MRG1/2 proteins as subunits of NuA4. MRGs recognize enriched H3K36me3 regions at FT chromatin, and via their MRG domain, physically interact with CO to enhance FT activation under LD inductive photoperiods. On the other hand, SWR1 mediates the deposition of H2A.Z at the TSS of FT chromatin, modulating its expression. See text for details. Scale bars refer to the size of coding regions of the genes from their respective TSS.