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. Author manuscript; available in PMC: 2019 Mar 1.
Published in final edited form as: Bioessays. 2018 Feb 6;40(3):10.1002/bies.201700208. doi: 10.1002/bies.201700208

Figure 6. Proposed model for origin initiation.

Figure 6

a) The Mcm2-7 hexamers are oriented head-to-head (N-to-N) at the origin. b) The PS1 loops of the Mcm2-7 DH track on the lagging strand and thus might pull it toward the central connection of the tight Mcm2-7 DH, producing ssDNA loops composed of the future lagging strand. c) The lagging ssDNA has been extruded outside the Mcm2-7 ring, and two CMGs have formed in S phase. d) the CMGs pass one another to leave the origin and produce bidirectional replication forks. Red arrows indicate the direction of DNA movement, and blue arrows indicate the direction of CMG movement. Adapted with permission from Figure 8 of [45] and Figure 6 of [67].