Figure 8.

Model for how the translocase activity of the SMARCAL1 HARP2-ATPase core catalyzes fork regression. Existing structures of SNF2 translocases demonstrate that ATPase-N and ATPase-C lobes are capable of adopting different relative conformations and suggest that such conformational changes (depicted as a circular arrow) in response to the ATPase-binding and hydrolysis cycle may drive translocation along dsDNA (Durr et al. 2005; Thoma et al. 2005; Lewis et al. 2008). The SAXS model shows that the HARP2 domain in SMARCAL1 is physically associated with the ATPase-N lobe and may aid in the specialized annealing activity through ssDNA or junction binding. Translocation displaces the nascent DNA strands, induces fork regression, and promotes junction migration.