Properties of the human Cdc45/Mcm2-7/GINS helicase complex and its action with DNA polymerase ε in rolling circle DNA synthesis

YH Kang, WC Galal, A Farina… - Proceedings of the …, 2012 - National Acad Sciences
YH Kang, WC Galal, A Farina, I Tappin, J Hurwitz
Proceedings of the National Academy of Sciences, 2012National Acad Sciences
In eukaryotes, although the Mcm2-7 complex is a key component of the replicative DNA
helicase, its association with Cdc45 and GINS (the CMG complex) is required for the
activation of the DNA helicase. Here, we show that the CMG complex is localized to
chromatin in human cells and describe the biochemical properties of the human CMG
complex purified from baculovirus-infected Sf9 cells. The isolated complex binds to ssDNA
regions in the presence of magnesium and ATP (or a nonhydrolyzable ATP analog) …
In eukaryotes, although the Mcm2-7 complex is a key component of the replicative DNA helicase, its association with Cdc45 and GINS (the CMG complex) is required for the activation of the DNA helicase. Here, we show that the CMG complex is localized to chromatin in human cells and describe the biochemical properties of the human CMG complex purified from baculovirus-infected Sf9 cells. The isolated complex binds to ssDNA regions in the presence of magnesium and ATP (or a nonhydrolyzable ATP analog), contains maximal DNA helicase in the presence of forked DNA structures, and translocates along the leading strand (3′ to 5′ direction). The complex hydrolyses ATP in the absence of DNA; unwinds duplex regions up to 500 bp; and either replication protein A or Escherichia coli single stranded binding protein increases the efficiency of displacement of long duplex regions. Using a 200-nt primed circular DNA substrate, the combined action of human DNA polymerase ε and the human CMG complex leads to the formation of products >10 kb in length. These findings suggest that the coordinated action of these replication complexes supports leading strand synthesis.
National Acad Sciences