Cold-sensitive mutants of p34(cdc2) that suppress a mitotic catastrophe phenotype in fission yeast
1992
Ayscough, K. | Hayles, J. | MacNeill, S.A. | Nurse, P.
The p34(cdc2) protein kinase plays a central role in the regulation of the eukaryotic cell cycle, being required both in late G1 for the commitment to S-phase and in late G2 for the initiation of mitosis. p34(cdc2) also determines the precise timing of entry into mitosis in fission yeast, where a number or gene products that regulate p34(cdc2) activity have been identified and characterised. To investigate further the mitotic role of p34(cdc2) in this organism we have isolated new cold-sensitive p34(cdc2) mutants. These are defective only in their G2 function and are extragenic suppressors of the lethal premature entry into mitosis brought about by mutating the mitotic inhibitor p107(wee1) and overproducing the mitotic activator p80(cdc25). One of the mutant proteins p34(cdc2-E8) is only functional in the absence of P107(wee1), and all the mutant strains have reduced histone H1 kinase activity in vitro. Each mutant allele has been cloned and sequenced, and the lesions responsible for the cold-sensitive phenotypes identified. All the mutations were found to map to regions that are conserved between the fission yeast p34(cdc2) and functional homologues from higher eukaryotes.
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