A fission yeast B-type cyclin functioning early in the cell cycle.
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.
Bueno
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Department of Molecular Biology, Research Institute of Scripps Clinic, La Jolla, California 92037.
Richardson
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Reed
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Russell
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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
D016213:Cyclins; D015345:Oligonucleotide Probes; D012333:RNA, Messenger