ジャーナル: Nat Commun / 年: 2017 タイトル: Cdt1 stabilizes an open MCM ring for helicase loading. 著者: Jordi Frigola / Jun He / Kerstin Kinkelin / Valerie E Pye / Ludovic Renault / Max E Douglas / Dirk Remus / Peter Cherepanov / Alessandro Costa / John F X Diffley / 要旨: ORC, Cdc6 and Cdt1 act together to load hexameric MCM, the motor of the eukaryotic replicative helicase, into double hexamers at replication origins. Here we show that Cdt1 interacts with MCM ...ORC, Cdc6 and Cdt1 act together to load hexameric MCM, the motor of the eukaryotic replicative helicase, into double hexamers at replication origins. Here we show that Cdt1 interacts with MCM subunits Mcm2, 4 and 6, which both destabilizes the Mcm2-5 interface and inhibits MCM ATPase activity. Using X-ray crystallography, we show that Cdt1 contains two winged-helix domains in the C-terminal half of the protein and a catalytically inactive dioxygenase-related N-terminal domain, which is important for MCM loading, but not for subsequent replication. We used these structures together with single-particle electron microscopy to generate three-dimensional models of MCM complexes. These show that Cdt1 stabilizes MCM in a left-handed spiral open at the Mcm2-5 gate. We propose that Cdt1 acts as a brace, holding MCM open for DNA entry and bound to ATP until ORC-Cdc6 triggers ATP hydrolysis by MCM, promoting both Cdt1 ejection and MCM ring closure.
CelldivisioncycleproteinCDT1 / SIC1 indispensable protein 2 / Topoisomerase-A hypersensitive protein 11
分子量: 49858.590 Da / 分子数: 3 / 断片: UNP residues 2-438 / 由来タイプ: 組換発現 詳細: Residues 1-438 of Cdt1 were recombinantly expressed and purified, residues which are missing in the structure were not defined in the electron density. 由来: (組換発現) Saccharomyces cerevisiae (パン酵母) 遺伝子: TAH11, CDT1, SID2, YJR046W, J1641 / 発現宿主: Escherichia coli (大腸菌) / 参照: UniProt: P47112