Figure 6. Nucleosomes remodeled by different CREs influence replication initiation differently.
Nucleosomes affect multiple steps of replication initiation using distinct mechanisms. Schematic of ATP-dependent nucleosome assembly with different CREs and their affect on replication initiation. Opacity of the nucleosome represents nucleosome density at each location. (A) Replication permissive nucleosomes are remodeled by ISW1a, ISW1b and INO80-C. These templates are competent for both origin licensing and origin activation. Nucleosome positioning is comparable in these templates. (B) SWI/SNF and RSC templates are origin-licensing competent but are inefficient for subsequent origin activation. We propose that the SWI/SNF and RSC templates have alternate/destabilized nucleosome structures indicated by their different color and that these nucleosomes are not conducive to origin activation. Although both reduce origin activation, SWI/SNF and RSC templates do not share similar nucleosome positioning. (C) ISW2 (and Chd1) templates have nucleosomes over the replication origin that reduce ORC DNA binding and, therefore, origin licensing.