To further investigate the functions of Mcm10 and MTC at a replication fork, we adapted the helicase substrate from Figure 5A–C to support DNA replication. The 3’ tail of the fork was extended to accommodate a primer for DNA synthesis and the reaction was staged as illustrated in Figure 5D. First, CMG was added with ATP to allow helicase translocation to the block, followed by Pol ε/RFC/PCNA/dNTPs to see if the ‘push’ on CMG from a Pol ε-PCNA motor can overcome the block. The results in Figure 5E lanes 1–3 show that Pol ε-PCNA extended the 32P-primer to the stalled CMG (~66 bp) but had limited ability to bypass the block to form the 141 bp full-length product. The ~91 bp bands result from forks lacking CMG, so Pol ε-PCNA extends to the fork but cannot proceed further because Pol ε lacks strand displacement capability and relies on CMG to unwind the DNA for leading strand synthesis (Ganai et al., 2016; Georgescu et al., 2014). MTC has little or no effect on block bypass by the replisome (Figure 5E lanes 7–9), and is comparable to Pol ε-PCNA-CMG in lanes 1–3. By contrast, addition of Mcm10 allows the replisome to efficiently and rapidly proceed past these blocks as evidenced by the appearance of full length 141 bp product in lanes 4–6. These results confirm that Mcm10 is needed for replisome bypass of a block and they also indicate that neither MTC nor Pol ε-PCNA is able to drive the forward movement of a stalled CMG in the absence of Mcm10.