title: A conserved MCM single-stranded DNA binding element is essential for replication initiation.
abstract: The ring-shaped MCM helicase is essential to all phases of DNA replication. The complex loads at replication origins as an inactive double-hexamer encircling duplex DNA. Helicase activation converts this species to two active single hexamers that encircle single-stranded DNA (ssDNA). The molecular details of MCM DNA interactions during these events are unknown. We determined the crystal structure of the Pyrococcus furiosus MCM N-terminal domain hexamer bound to ssDNA and define a conserved MCM-ssDNA binding motif (MSSB). Intriguingly, ssDNA binds the MCM ring interior perpendicular to the central channel with defined polarity. In eukaryotes, the MSSB is conserved in several Mcm2-7 subunits, and MSSB mutant combinations in S. cerevisiae Mcm2-7 are not viable. Mutant Mcm2-7 complexes assemble and are recruited to replication origins, but are defective in helicase loading and activation. Our findings identify an important MCM-ssDNA interaction and suggest it functions during helicase activation to select the strand for translocation. DOI: http://dx.doi.org/10.7554/eLife.01993.001.
authors.affiliation: Department of Structural Biology, St Jude Children's Research Hospital, Memphis, United States.
authors.forename: Clifford A
authors.initials: CA
authors.lastname: Froelich
authors.forename: Sukhyun
authors.initials: S
authors.lastname: Kang
authors.forename: Leslie B
authors.initials: LB
authors.lastname: Epling
authors.forename: Stephen P
authors.initials: SP
authors.lastname: Bell
authors.forename: Eric J
authors.initials: EJ
authors.lastname: Enemark
mesh_terms: D000595:Amino Acid Sequence; D017124:Conserved Sequence; D018360:Crystallography, X-Ray; D004261:DNA Replication / Q000502:physiology*; D004277:DNA, Single-Stranded / Q000737:chemistry / Q000378:metabolism*; D064110:Minichromosome Maintenance Proteins / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D008969:Molecular Sequence Data; D011487:Protein Conformation; D020027:Pyrococcus furiosus / Q000201:enzymology; D012441:Saccharomyces cerevisiae / Q000201:enzymology; D017386:Sequence Homology, Amino Acid
chemical_list: D004277:DNA, Single-Stranded; D064110:Minichromosome Maintenance Proteins
keywords: DNA replication; archaea; crystallography; genetics; helicase