FIG. 8.

Proposed model of Swi1's involvement in the response to fork arrest. Swi1 is recruited to chromatin during S phase, suggesting that it might be an ancillary component of the replisome. Swi1 is required for proficient activation of Cds1 in response to replication arrest, suggesting that it stabilizes the stalled fork in a conformation that is recognized by the checkpoint sensor proteins (Rad3-Rad26 and Rad9-Rad1-Hus1 complexes) and Mrc1. Mrc1 facilities Cds1 activation by recruiting it to Rad3 and/or mediating Cds1 autophosphorylation. Cds1 enhances fork and replisome stabilization while the lesion is removed.