Figure 3.

The deposition of distinct H3 variant proteins involves the activity of multiple distinct chaperone complexes. (a) The replication-coupled deposition of H3.1/H3.2 is mediated by the chromatin-assembly factor 1 (CAF1) complex in association with the proliferating cell nuclear antigen (PCNA-a processivity factor for DNA polymerase in eukaryotic cells). (b) Replication-independent deposition of H3.3, however, is mediated by several HIRA complexes acting throughout genic regions of the genome, as well as by other unidentified complexes associated with H3.3 deposition at specific regulatory element (RE)-binding sites. Pericentromeric and telomeric deposition of H3.3 (not shown here, but see Figure 2) are carried out by ATRX/Daxx complexes.