6WGF

Atomic model of mutant Mcm2-7 hexamer with Mcm6 WHD truncation

Summary for 6WGF

• Entry DOI: 10.2210/pdb6wgf/pdb
• EMDB information: 21662 21664 21665 21666
• Descriptor: DNA replication licensing factor MCM2, DNA replication licensing factor MCM7, DNA replication licensing factor MCM6, ... (6 entities in total)
• Functional Keywords: dna replication, cryo-em, occm-deltac6, replication
• Biological source: Saccharomyces cerevisiae (Baker's yeast); More
• Total number of polymer chains: 6
• Total formula weight: 606369.24

Authors

Yuan, Z.,Schneider, S.,Dodd, T.,Riera, A.,Bai, L.,Yan, C.,Magdalou, I.,Ivanov, I.,Stillman, B.,Li, H.,Speck, C. (deposition date: 2020-04-05, release date: 2020-07-15, Last modification date: 2024-03-06)

Primary citation

Yuan, Z.,Schneider, S.,Dodd, T.,Riera, A.,Bai, L.,Yan, C.,Magdalou, I.,Ivanov, I.,Stillman, B.,Li, H.,Speck, C.
Structural mechanism of helicase loading onto replication origin DNA by ORC-Cdc6.
Proc.Natl.Acad.Sci.USA, 117:17747-17756, 2020

PubMed Abstract: DNA replication origins serve as sites of replicative helicase loading. In all eukaryotes, the six-subunit origin recognition complex (Orc1-6; ORC) recognizes the replication origin. During late M-phase of the cell-cycle, Cdc6 binds to ORC and the ORC-Cdc6 complex loads in a multistep reaction and, with the help of Cdt1, the core Mcm2-7 helicase onto DNA. A key intermediate is the ORC-Cdc6-Cdt1-Mcm2-7 (OCCM) complex in which DNA has been already inserted into the central channel of Mcm2-7. Until now, it has been unclear how the origin DNA is guided by ORC-Cdc6 and inserted into the Mcm2-7 hexamer. Here, we truncated the C-terminal winged-helix-domain (WHD) of Mcm6 to slow down the loading reaction, thereby capturing two loading intermediates prior to DNA insertion in budding yeast. In "semi-attached OCCM," the Mcm3 and Mcm7 WHDs latch onto ORC-Cdc6 while the main body of the Mcm2-7 hexamer is not connected. In "pre-insertion OCCM," the main body of Mcm2-7 docks onto ORC-Cdc6, and the origin DNA is bent and positioned adjacent to the open DNA entry gate, poised for insertion, at the Mcm2-Mcm5 interface. We used molecular simulations to reveal the dynamic transition from preloading conformers to the loaded conformers in which the loading of Mcm2-7 on DNA is complete and the DNA entry gate is fully closed. Our work provides multiple molecular insights into a key event of eukaryotic DNA replication.

PubMed: 32669428
DOI: 10.1073/pnas.2006231117

Experimental method

ELECTRON MICROSCOPY (7.7 Å)