A role for Ran-GTP and Crm1 in blocking re-replication.
All eukaryotic cells have regulatory mechanisms that limit genomic replication to a single round each cell cycle. These systems function by blocking formation of prereplication complexes. The regulatory mechanisms in the yeast S. cerevisiae have been identified, but these do not appear to be conserved in metazoans. Using Xenopus egg extracts, we have identified a metazoan-specific regulatory system that limits replication to a single round. We show that during S phase, soluble MCM helicase, an essential initiation factor, is inactivated when it associates with exportin-1/Crm1. Formation of this complex is dependent on both high Ran-GTP and cdk2 kinase activity. Lowering Ran-GTP within nuclei or nuclear extracts allows MCM to reassociate with chromatin during S phase and induces re-replication. Importantly, prevention of re-replication requires MCM-Crm1 complex formation, but it does not require export of MCM from the nucleus. Therefore, in metazoans, Crm1 functions in both nuclear export and blocking of re-replication.
Yamaguchi
Ryuji
R
Department of Biology, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA.
Newport
John
J
D021581:Active Transport, Cell Nucleus / Q000235:genetics*; D000818:Animals; D001665:Binding Sites / Q000187:drug effects / Q000235:genetics; D042846:CDC2-CDC28 Kinases; D018797:Cell Cycle Proteins / Q000235:genetics* / Q000378:metabolism; D002457:Cell Extracts; D002467:Cell Nucleus / Q000201:enzymology*; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases / Q000235:genetics / Q000378:metabolism; D004265:DNA Helicases / Q000235:genetics / Q000378:metabolism; D004261:DNA Replication / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D005057:Eukaryotic Cells / Q000201:enzymology*; D005260:Female; D020690:GTPase-Activating Proteins / Q000378:metabolism / Q000494:pharmacology; D064248:Geminin; D028884:Karyopherins / Q000235:genetics / Q000378:metabolism*; D026341:Minichromosome Maintenance 1 Protein / Q000235:genetics / Q000378:metabolism; D009687:Nuclear Proteins / Q000378:metabolism / Q000494:pharmacology; D009865:Oocytes; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism; D018160:Receptors, Cytoplasmic and Nuclear; D016196:S Phase / Q000235:genetics; D029867:Xenopus Proteins; D014982:Xenopus laevis; D020931:ran GTP-Binding Protein / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D000097606:Exportin 1 Protein
D042846:CDC2-CDC28 Kinases; D018797:Cell Cycle Proteins; D002457:Cell Extracts; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases; D004265:DNA Helicases; D004268:DNA-Binding Proteins; D020690:GTPase-Activating Proteins; D064248:Geminin; D028884:Karyopherins; D026341:Minichromosome Maintenance 1 Protein; D009687:Nuclear Proteins; D017346:Protein Serine-Threonine Kinases; D018160:Receptors, Cytoplasmic and Nuclear; D029867:Xenopus Proteins; D020931:ran GTP-Binding Protein; D000097606:Exportin 1 Protein; C577998:GMNN protein, Xenopus; C513268:RanGAP1 protein, Xenopus; C091775:ran-binding protein 1; C495891:Cdk2 protein, Xenopus