MCM8 is an MCM2-7-related protein that functions as a DNA helicase during replication elongation and not initiation.
MCM2-7 proteins are replication factors required to initiate DNA synthesis and are currently the best candidates for replicative helicases. We show that the MCM2-7-related protein MCM8 is required to efficiently replicate chromosomal DNA in Xenopus egg extracts. MCM8 does not associate with the soluble MCM2-7 complex and binds chromatin upon initiation of DNA synthesis. MCM8 depletion does not affect replication licensing or MCM3 loading but slows down DNA synthesis and reduces chromatin recruitment of RPA34 and DNA polymerase-alpha. Recombinant MCM8 displays both DNA helicase and ATPase activities in vitro. Reconstitution experiments show that ATP binding in MCM8 is required to rescue DNA synthesis in MCM8-depleted extracts. MCM8 colocalizes with replication foci and RPA34 on chromatin. We suggest that MCM8 functions in the elongation step of DNA replication as a helicase that facilitates the recruitment of RPA34 and stimulates the processivity of DNA polymerases at replication foci.
Maiorano
Domenico
D
Institute of Human Genetics, Centre National de la Recherche Scientifique, 141 rue de la Cardonille, 34396 Montpellier Cedex 05, France.
Cuvier
Olivier
O
Danis
Etienne
E
Méchali
Marcel
M
D000251:Adenosine Triphosphatases / Q000378:metabolism; D000818:Animals; D018797:Cell Cycle Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D002875:Chromosomes / Q000502:physiology*; D004247:DNA / Q000096:biosynthesis; D004265:DNA Helicases / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D004256:DNA Polymerase I / Q000378:metabolism; D004261:DNA Replication / Q000502:physiology*; D004268:DNA-Binding Proteins / Q000378:metabolism; D015536:Down-Regulation / Q000502:physiology; D005260:Female; D064111:Minichromosome Maintenance Complex Component 2; D064110:Minichromosome Maintenance Proteins; D008938:Mitosis / Q000235:genetics*; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D009865:Oocytes; D011817:Rabbits; D014981:Xenopus; D029867:Xenopus Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*
D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; C490673:RPAp34 protein, rat; D029867:Xenopus Proteins; D004247:DNA; D004256:DNA Polymerase I; D000251:Adenosine Triphosphatases; D004265:DNA Helicases; C084859:MCM2 protein, human; C498047:MCM8 protein, Xenopus; C471623:MCM8 protein, human; D064111:Minichromosome Maintenance Complex Component 2; D064110:Minichromosome Maintenance Proteins