A CAF-1-PCNA-mediated chromatin assembly pathway triggered by sensing DNA damage

Sensing DNA damage is crucial for the maintenance of genomic integrity and cell cycle progression. The participation of chromatin in these events is b ecoming of increasing interest. We show that the presence of single-strand breaks and gaps, formed either directly or during DNA damage processing, ca n trigger the propagation of nucleosomal arrays. This nucleosome assembly p athway involves the histone chaperone chromatin assembly factor 1 (CAF-1). The largest subunit (p150) of this factor interacts directly with prolifera ting cell nuclear antigen (PCNA), and critical regions for this interaction on both proteins have been mapped. To isolate proteins specifically recrui ted during DNA repair, damaged DNA linked to magnetic beads was used. The b inding of both PCNA and CAF-1 to this damaged DNA nas dependent on the numb er of DNA lesions and required ATP. Chromatin assembly linked to the repair of single-strand breaks was disrupted by depletion of PCNA from a cell-fre e system. This defect was rescued by complementation with recombinant PCNA, arguing for role of PCNA in mediating chromatin assembly linked to DNA rep air. We discuss the importance of the PCNA-CAF-1 interaction in the contest of DNA damage processing and checkpoint control.