title: Structure of human Cdc45 and implications for CMG helicase function.
abstract: Cell division cycle protein 45 (Cdc45) is required for DNA synthesis during genome duplication, as a component of the Cdc45-MCM-GINS (CMG) helicase. Despite its essential biological function, its biochemical role in DNA replication has remained elusive. Here we report the 2.1-Å crystal structure of human Cdc45, which confirms its evolutionary link with the bacterial RecJ nuclease and reveals several unexpected features that underpin its function in eukaryotic DNA replication. These include a long-range interaction between N- and C-terminal DHH domains, blocking access to the DNA-binding groove of its RecJ-like fold, and a helical insertion in its N-terminal DHH domain, which appears poised for replisome interactions. In combination with available electron microscopy data, we validate by mutational analysis the mechanism of Cdc45 association with the MCM ring and GINS co-activator, critical for CMG assembly. These findings provide an indispensable molecular basis to rationalize the essential role of Cdc45 in genomic duplication.
authors.affiliation: Department of Biochemistry, University of Cambridge, Cambridge CB2 1GA, UK.
authors.forename: Aline C
authors.initials: AC
authors.lastname: Simon
authors.affiliation: DNA Metabolism Laboratory, FIRC Institute of Molecular Oncology Foundation, 20139 Milan, Italy.
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Sannino
authors.affiliation: DNA Metabolism Laboratory, FIRC Institute of Molecular Oncology Foundation, 20139 Milan, Italy.
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Costanzo
authors.affiliation: Department of Biochemistry, University of Cambridge, Cambridge CB2 1GA, UK.
authors.forename: Luca
authors.identifier: 0000-0002-9300-497X
authors.initials: L
authors.lastname: Pellegrini
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001426:Bacterial Proteins / Q000737:chemistry; D018797:Cell Cycle Proteins / Q000737:chemistry* / Q000378:metabolism; D002868:Chromosomal Proteins, Non-Histone / Q000378:metabolism; D018360:Crystallography, X-Ray; D004265:DNA Helicases / Q000378:metabolism; D004261:DNA Replication; D005090:Exodeoxyribonucleases / Q000737:chemistry; D005260:Female; D006801:Humans; D064110:Minichromosome Maintenance Proteins / Q000378:metabolism; D011487:Protein Conformation; D014982:Xenopus laevis
chemical_list: D001426:Bacterial Proteins; C113571:CDC45 protein, human; D018797:Cell Cycle Proteins; D002868:Chromosomal Proteins, Non-Histone; D005090:Exodeoxyribonucleases; C070765:recJ protein, Bacteria; D004265:DNA Helicases; D064110:Minichromosome Maintenance Proteins