title: A fission yeast B-type cyclin functioning early in the cell cycle.
abstract: We have cloned a fission yeast gene, cig1+, encoding a 48 kd product that is most similar to cyclin B proteins. The cig1+ protein has a "cyclin box" approximately 40% identical to B-type cyclins of other species, but lacks the "destruction box" required for proteolysis of mitotic cyclins. Deletion of cig1+ had no observable effect on cell viability or progression through G2 or M phase, but instead caused a marked lag in the progression from G1 to S phase. G1 constituted approximately 70% of the cell cycle in cig1 deletion strains, as compared with less than 10% in cig1+ strains. Constitutive cig1+ overexpression was lethal, causing cessation of growth and arrest in G1. Expression of cig1+ failed to rescue an S. cerevisiae strain lacking CLN Start cyclins. Thus, cig1+ identifies a new class of B-type cyclin acting in G1 or S phase that appears to be functionally distinct from all previously described cyclin proteins.
authors.affiliation: Department of Molecular Biology, Research Institute of Scripps Clinic, La Jolla, California 92037.
authors.forename: A
authors.initials: A
authors.lastname: Bueno
authors.forename: H
authors.initials: H
authors.lastname: Richardson
authors.forename: S I
authors.initials: SI
authors.lastname: Reed
authors.forename: P
authors.initials: P
authors.lastname: Russell
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D002453:Cell Cycle / Q000235:genetics; D002872:Chromosome Deletion; D003001:Cloning, Molecular; D016213:Cyclins / Q000235:genetics* / Q000502:physiology; D005800:Genes, Fungal; D008969:Molecular Sequence Data; D015345:Oligonucleotide Probes; D016366:Open Reading Frames; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D015183:Restriction Mapping; D012568:Schizosaccharomyces / Q000166:cytology / Q000235:genetics* / Q000254:growth & development; D012689:Sequence Homology, Nucleic Acid
chemical_list: D016213:Cyclins; D015345:Oligonucleotide Probes; D012333:RNA, Messenger