title: CDK phosphorylation of a novel NLS-NES module distributed between two subunits of the Mcm2-7 complex prevents chromosomal rereplication.
abstract: Cyclin-dependent kinases (CDKs) use multiple mechanisms to block reassembly of prereplicative complexes (pre-RCs) at replication origins to prevent inappropriate rereplication. In Saccharomyces cerevisiae, one of these mechanisms promotes the net nuclear export of a pre-RC component, the Mcm2-7 complex, during S, G2, and M phases. Here we identify two partial nuclear localization signals (NLSs) on Mcm2 and Mcm3 that are each necessary, but not sufficient, for nuclear localization of the Mcm2-7 complex. When brought together in cis, however, the two partial signals constitute a potent NLS, sufficient for robust nuclear localization when fused to an otherwise cytoplasmic protein. We also identify a Crm1-dependent nuclear export signal (NES) adjacent to the Mcm3 NLS. Remarkably, the Mcm2-Mcm3 NLS and the Mcm3 NES are sufficient to form a transport module that recapitulates the cell cycle-regulated localization of the entire Mcm2-7 complex. Moreover, we show that CDK regulation promotes net export by phosphorylation of the Mcm3 portion of this module and that nuclear export of the Mcm2-7 complex is sufficient to disrupt replication initiation. We speculate that the distribution of partial transport signals among distinct subunits of a complex may enhance the specificity of protein localization and raises the possibility that previously undetected distributed transport signals are used by other multiprotein complexes.
authors.affiliation: Department of Biochemistry, University of California, San Francisco, CA 94143-2200, USA.
authors.forename: Muluye E
authors.initials: ME
authors.lastname: Liku
authors.forename: Van Q
authors.initials: VQ
authors.lastname: Nguyen
authors.forename: Audrey W
authors.initials: AW
authors.lastname: Rosales
authors.forename: Kaoru
authors.initials: K
authors.lastname: Irie
authors.forename: Joachim J
authors.initials: JJ
authors.lastname: Li
mesh_terms: D000595:Amino Acid Sequence; D017489:CDC28 Protein Kinase, S cerevisiae / Q000378:metabolism*; D002453:Cell Cycle; D018797:Cell Cycle Proteins / Q000378:metabolism*; D002868:Chromosomal Proteins, Non-Histone; D015825:Chromosomes, Fungal / Q000502:physiology*; D004261:DNA Replication; D004268:DNA-Binding Proteins / Q000378:metabolism; D005656:Fungal Proteins / Q000378:metabolism*; D028884:Karyopherins / Q000378:metabolism; D064126:Minichromosome Maintenance Complex Component 3; D064148:Minichromosome Maintenance Complex Component 4; D064151:Minichromosome Maintenance Complex Component 6; D064168:Minichromosome Maintenance Complex Component 7; D008969:Molecular Sequence Data; D019913:Nuclear Localization Signals / Q000378:metabolism*; D009687:Nuclear Proteins / Q000378:metabolism*; D010766:Phosphorylation; D021122:Protein Subunits / Q000378:metabolism; D021381:Protein Transport; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000502:physiology* / Q000648:ultrastructure; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*; D000097606:Exportin 1 Protein
chemical_list: D017489:CDC28 Protein Kinase, S cerevisiae; D018797:Cell Cycle Proteins; D002868:Chromosomal Proteins, Non-Histone; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; D028884:Karyopherins; D064126:Minichromosome Maintenance Complex Component 3; D064148:Minichromosome Maintenance Complex Component 4; D064151:Minichromosome Maintenance Complex Component 6; D064168:Minichromosome Maintenance Complex Component 7; D019913:Nuclear Localization Signals; D009687:Nuclear Proteins; D021122:Protein Subunits; D018160:Receptors, Cytoplasmic and Nuclear; D029701:Saccharomyces cerevisiae Proteins; D000097606:Exportin 1 Protein; C069200:MCM5 protein, S cerevisiae; C069199:MCM2 protein, S cerevisiae; C507761:MCM3 protein, S cerevisiae; C092802:MCM4 protein, S cerevisiae; C491207:MCM6 protein, S cerevisiae; C491088:MCM7 protein, S cerevisiae