title: MCM3 complex required for cell cycle regulation of DNA replication in vertebrate cells.
abstract: An intact nuclear membrane restricts DNA replication to only one round in each cell cycle, apparently by excluding an essential replication-licensing factor throughout interphase. A family of related yeast replication proteins, MCM2, 3 and 5 (also called, after cell-division cycle, CDC46), resemble licensing factor, entering the nucleus only during mitosis. We have cloned a Xenopus homologue of MCM3 (XMCM3) and raised antibodies against expressed protein. Immunodepletion of Xenopus egg extracts removes a complex of MCM2, 3 and 5 homologues and inhibits replication of Xenopus sperm nuclei or permeable G2 HeLa nuclei. However, G1 HeLa nuclei still replicate efficiently. Mock-depleted extracts replicate all three templates. XMCM3 accumulates in nuclei before replication but anti-XMCM3 staining decreases during replication. These results can explain why replicated nuclei are unable to reinitiate replication in a single cell cycle.
authors.affiliation: Wellcome/CRC Institute, Cambridge, UK.
authors.forename: M A
authors.initials: MA
authors.lastname: Madine
authors.forename: C Y
authors.initials: CY
authors.lastname: Khoo
authors.forename: A D
authors.initials: AD
authors.lastname: Mills
authors.forename: R A
authors.initials: RA
authors.lastname: Laskey
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002453:Cell Cycle / Q000502:physiology*; D018797:Cell Cycle Proteins / Q000502:physiology*; D003001:Cloning, Molecular; D017931:DNA Primers; D004261:DNA Replication / Q000502:physiology*; D004268:DNA-Binding Proteins; D005656:Fungal Proteins / Q000502:physiology; D006367:HeLa Cells; D006801:Humans; D008297:Male; D064126:Minichromosome Maintenance Complex Component 3; D008969:Molecular Sequence Data; D009687:Nuclear Proteins; D009865:Oocytes; D012441:Saccharomyces cerevisiae / Q000235:genetics; D013094:Spermatozoa; D014982:Xenopus laevis
chemical_list: D018797:Cell Cycle Proteins; D017931:DNA Primers; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; C066470:MCM3 protein, human; D009687:Nuclear Proteins; D064126:Minichromosome Maintenance Complex Component 3