Abstract
When DNA replication is stalled at sites of DNA damage, a cascade of responses is activated in the cell to halt cell cycle progression and promote DNA repair. A pathway initiated by the kinase ATR and its partner ATRIP plays an important role in this response. Replication stress activates ATRIP-ATR via two distinct steps: first by local chromatin accumulation of the kinase through binding to the RPA-coated single stranded DNA; and second by direct association of ATRIP-ATR with the activation domain of TopBP1, leading to the increased kinase activity and Chk1 phosphorylation. Here we show evidence that the Fanconi anemia (FA) pathway is activated following genomic stress in a manner dependent on ATR. Furthermore, we have found that, following cellular exposure to DNA crosslinking damage, FA cells deficient in the core complex components have a defect in the first accumulation step in ATR signaling, and that the FA core complex but not FANCD2 enhances binding and localization of ATRIP within damaged chromatin. In cells lacking the core complex, ATR mediated phosphorylation of two functional response targets, ATRIP and FANCI, is defective. Our data now reveal a new mode of regulation of the ATR pathway via action of the multisubunit FA complex.
