title: Cyclin A promotes S-phase entry via interaction with the replication licensing factor Mcm7.
abstract: Cyclin A is known to promote S-phase entry in mammals, but its critical targets in this process have not been defined. We derived a novel human cyclin A mutant (CycA-C1), which can activate cyclin-dependent kinase but cannot promote S-phase entry, and isolated replication licensing factor Mcm7 as a factor that interacts with the wild-type cyclin A but not with the mutant. We demonstrated that human cyclin A and Mcm7 interact in the chromatin fraction. To address the physiological significance of the cyclin A-Mcm7 interaction, we isolated an Mcm7 mutant (Mcm7-3) that is capable of association with CycA-C1 and found that it can also suppress the deficiency of CycA-C1 in promoting S-phase entry. Finally, RNA interference experiments showed that the CycA-C1 mutant is defective for the endogenous cyclin A function in S-phase entry and that this defect can be suppressed by the Mcm7-3 mutant. Our findings demonstrate that interaction with Mcm7 is essential for the function of cyclin A in promoting S-phase entry.
authors.affiliation: Department of Bioscience, Tokyo University of Agriculture, 1-1-1 Sakuragaoka, Setagaya-ku, Tokyo 156-8502, Japan. taku@nodai.ac.jp
authors.forename: Taku
authors.initials: T
authors.lastname: Chibazakura
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Kamachi
authors.forename: Mayu
authors.initials: M
authors.lastname: Ohara
authors.forename: Shoji
authors.initials: S
authors.lastname: Tane
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Yoshikawa
authors.forename: James M
authors.initials: JM
authors.lastname: Roberts
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D019925:Cyclin A / Q000235:genetics / Q000378:metabolism*; D004261:DNA Replication; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D051379:Mice; D064168:Minichromosome Maintenance Complex Component 7; D008969:Molecular Sequence Data; D009154:Mutation; D041681:NIH 3T3 Cells; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D034622:RNA Interference; D016196:S Phase; D020798:Two-Hybrid System Techniques
chemical_list: D018797:Cell Cycle Proteins; D019925:Cyclin A; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; C101624:MCM7 protein, human; D064168:Minichromosome Maintenance Complex Component 7