Mec1 is recruited to RPA-ssDNA following DNA damage to promote Rad53-mediated checkpoint signaling that prevents immediate long-range resection of DNA ends. This anti-resection function of Mec1 is important to protect DNA ends and ensure that subsequent resection occurs in a restrained and controllable manner. Since the Dpb11-Rad9 interaction is not dependent on Mec1 (but mostly dependent on CDK phosphorylation), the Dpb11-Rad9 complex is rapidly stabilized at DNA lesions once initial Mec1 signaling and Ddc1 phosphorylation occurs. As Mec1 signaling builds up, it hyper-phosphorylates the Slx4 scaffold, which becomes a strong interactor of Dpb11 and displaces Rad9 to counteract checkpoint signaling and Rad9-mediated resection block. Mec1 signaling therefore switches to an anti-checkpoint and pro-resection mode. Once long-resection occurs, extensive ssDNA accumulates, leading to increased opportunities for strand invasion, but also increased opportunities for non-allelic recombination (rad9∆ cells have increased non-allelic recombination (Fasullo et al, 1998; Nielsen et al, 2013)). In this context, we propose that a new mode of Mec1 signaling triggered by extensive resection stabilizes the STR complex at lesions via interaction with Dpb11 for proper regulation of HR. It is tempting to speculate that the Dpb11-9-1-1 complex acts as a "processivity factor" for the helicase function of Sgs1 to processively displace, and reject, heteroduplexes. 