The single Cdk1-G1 cyclin of Cryptococcus neoformans is not essential for cell cycle progression, but plays important roles in the proper commitment to DNA synthesis and bud emergence in this yeast.
The cell cycle pattern of the pathogenic basidiomycetous yeast Cryptococcus neoformans differs from that of the ascomycetous budding yeast Saccharomyces cerevisiae. To clarify the cell cycle control mechanisms at the molecular level, homologues of cell cycle control genes in C. neoformans were cloned and analyzed. Here, we report on the cloning and characterization of genes coding for CDK1 cyclin homologues, in particular, the C. neoformans G1 cyclin. We have identified three putative CDK1 cyclin homologues and two putative CDK5 (PHO85) cyclin homologues from the genome. Complementation tests in an S. cerevisiae G1 cyclin triple mutant confirmed that C. neoformans CLN1 is able to complement S. cerevisiae G1 cyclin deficiency, demonstrating that it is a G1 cyclin homologue. Interestingly, cells deleted of the single Cdk1-G1 cyclin were viable, demonstrating that this gene is not essential. However, it exhibited aberrant budding and cell division and a clear delay in the initiation of DNA synthesis as well as an extensive delay in budding. The fact that the mutant managed to traverse the G1 to M phase may be due to the activities of Pho85-related G1 cyclins. Also, that C. neoformans had only a single Cdk1-G1 cyclin highlighted the importance of keeping in order the commitment to the initiation of DNA synthesis first and then that of budding, as discussed.
Medical Mycology Research Center, Division of Molecular Biology, Chiba University, Chuo-ku, Chiba, Japan.
Eric V
EV
Virtudazo
Susumu
S
Kawamoto
Misako
M
Ohkusu
Shigeji
S
Aoki
Matthias
M
Sipiczki
Kanji
K
Takeo
D000595:Amino Acid Sequence; D016203:CDC2 Protein Kinase / Q000235:genetics* / Q000378:metabolism*; D002453:Cell Cycle; D003001:Cloning, Molecular; D019295:Computational Biology; D003455:Cryptococcus neoformans / Q000166:cytology / Q000201:enzymology* / Q000502:physiology*; D051360:Cyclin-Dependent Kinase 5 / Q000235:genetics / Q000378:metabolism; D004271:DNA, Fungal / Q000096:biosynthesis*; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism; D017353:Gene Deletion; D005816:Genetic Complementation Test; D016681:Genome, Fungal; D050296:Microbial Viability; D008969:Molecular Sequence Data; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000254:growth & development; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
D004271:DNA, Fungal; D005656:Fungal Proteins; D051360:Cyclin-Dependent Kinase 5; D016203:CDC2 Protein Kinase