Nik1: a Nim1-like protein kinase of S. cerevisiae interacts with the Cdc28 complex and regulates cell cycle progression.
BACKGROUND
The eukaryotic cell cycle is driven by CDK-cyclin complexes. A number of proteins interact either with CDK or the CDK complex to regulate CDK activity. A search for novel cell cycle regulators in the budding yeast Saccharomyces cerevisiae yielded multicopy suppressors of the cdc2-L7 mutation of the fission yeast, Schizosaccharomyces pombe.


RESULTS
One of the isolated genes was found to encode a putative protein kinase similar to Nim1 of S. pombe and was termed NIK1 (Nim1-like kinase 1). Transcription of NIK1 was periodic and peaked at the G1/S boundary. Although NIK1 is not essential, delta nik1 cells showed G2 delay and hydroxyurea (HU) sensitivity. Anomalously elongated buds were observed in the stationary phase or in the presence of HU. Moreover, DNA was aberrantly distributed in the delta nik1 cdc28 double mutant. Genetical and biochemical evidence suggests that Nik1 interacts with the Cdc28 complex.


CONCLUSIONS
Nik is a structural and functional homologue of Nim1. Nik1 interacts with the Cdc28 complex and functions not only at the G2/M transition but also at other points of the cell cycle.
Tanaka
S
S
Department of Molecular Genetics, Research Institute for Microbial Diseases, Osaka University, Suita City, Japan.
Nojima
H
H
D000595:Amino Acid Sequence; D017489:CDC28 Protein Kinase, S cerevisiae / Q000502:physiology*; D002453:Cell Cycle / Q000502:physiology*; D018797:Cell Cycle Proteins / Q000502:physiology; D002455:Cell Division / Q000187:drug effects; D003001:Cloning, Molecular; D016195:G2 Phase; D006918:Hydroxyurea / Q000494:pharmacology; D008938:Mitosis; D008969:Molecular Sequence Data; D010641:Phenotype; D010749:Phosphoprotein Phosphatases / Q000502:physiology; D011494:Protein Kinases / Q000235:genetics / Q000502:physiology*; D017346:Protein Serine-Threonine Kinases; D012441:Saccharomyces cerevisiae / Q000166:cytology* / Q000201:enzymology*; D029701:Saccharomyces cerevisiae Proteins; D012568:Schizosaccharomyces / Q000166:cytology; D017386:Sequence Homology, Amino Acid; D013489:Suppression, Genetic; D020687:cdc25 Phosphatases
D018797:Cell Cycle Proteins; D029701:Saccharomyces cerevisiae Proteins; D011494:Protein Kinases; C106494:HSL1 protein, S cerevisiae; D017346:Protein Serine-Threonine Kinases; D017489:CDC28 Protein Kinase, S cerevisiae; D010749:Phosphoprotein Phosphatases; D020687:cdc25 Phosphatases; D006918:Hydroxyurea