Mcm10 binds remarkably tightly to CMG, eluting as a CMG-Mcm10 complex from beads after high salt washes (Figure 2D), and the CMG-Mcm10 complex also remains associated and elutes from a MonoQ ion-exchange resin at high ionic strength (400–450 mM NaCl) (Figure 2—figure supplement 4). Additionally, some studies suggest Mcm10 is a component of moving replisomes (Chadha et al., 2016; Gambus et al., 2006; Lõoke et al., 2017; Ricke and Bielinsky, 2004). However, other cellular studies indicate that Mcm10 is not in constant association with the replisome (Kanke et al., 2012; van Deursen et al., 2012; Watase et al., 2012). Thus, while the salt stability of the CMG-Mcm10 complex reported here suggests it might remain attached to the replisome, its kinetics of attachment are not addressed here and Mcm10 could still be dynamic with CMG, or its on/off rates with the replisome could be affected by other proteins in the cell. Future structural and single-molecule studies of CMG-Mcm10 may be expected to shed light on further details about the dynamics of Mcm10 and the mechanism of its replisome bypass function at stalled replisomes described in this report.