Figure 3.

Local enrichment of H3.3 and complexes promoting deposition. Left: in mouse somatic and embryonic cells, H3.3 is enriched in coding regions and at specific chromatin landmarks. In heterochromatin, DAXX cooperates with the chromatin remodeler ATRX in accumulating H3.3 at pericentric heterochromatin and telomeres. It has to be noticed that accumulation of H3.3 at telomeres is so far only described in ES cells. In euchromatin, the HIRA complex mediates H3.3 enrichment in the body of transcribed genes and at promoters of transcribed or non-transcribed genes. The chaperone complex that mediates H3.3 enrichment at regulatory elements remains to be clearly identified but DAXX and/or DEK proteins have been suggested to play a role in this process. Right: in gametes, H3.3 is enriched in sex chromosomes during mouse male meiosis during MSCI. HIRA and DAXX colocalize with XY bodies but their potential role in this process still needs to be uncovered. In zygotes, H3.3 is loaded in the male pronucleus at fertilization in Drosophila and in mouse through the HIRA complex that cooperates with the chromatin remodeling factor CHD1.