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Studying Cell Cycle-regulated Gene Expression by Two Complementary Cell Synchronization Protocols
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Negative regulation of mitosis by wee1+, a gene encoding a protein kinase homolog

P Russell, P Nurse

    Cell
    |May 22, 1987
    PubMed

    Insights

    Fission yeast wee1 mutants initiate mitosis prematurely. Wee1+ protein acts as a dose-dependent inhibitor, delaying mitosis until cells reach a larger size, revealing a key regulator of cell cycle progression.

    Area of Science:

    • Cell biology
    • Molecular genetics
    • Biochemistry

    Background:

    • Fission yeast cell cycle regulation is crucial for proper cell division.
    • The protein kinase cdc2+ is essential for initiating mitosis.
    • cdc25+ is a known inducer of mitosis.

    Purpose of the Study:

    • To identify and clone the gene responsible for inhibiting premature mitosis in fission yeast.
    • To elucidate the role of the identified gene in cell size control and mitotic entry.
    • To understand the regulatory mechanism involving wee1+ and cdc25+ in the cell cycle.

    Main Methods:

    • Complementation cloning using a lethal premature mitosis phenotype.
    • Genetic analysis of gene function and interactions.
    • Biochemical analysis of protein domains and kinase activity.

    Main Results:

    • Fission yeast wee1- mutants initiate mitosis at a significantly smaller cell size.
    • Wee1+ activity is essential for preventing lethal premature mitosis induced by cdc25+.
    • Increased wee1+ expression delays mitotic entry until cells reach a larger size.
    • The wee1+ protein contains kinase consensus sequences, suggesting a role in phosphorylation.
    • Wee1+ and cdc25+ compete to regulate the cdc2+ protein kinase.

    Conclusions:

    • Wee1+ functions as a dose-dependent inhibitor of mitosis, acting as a critical cell size checkpoint.
    • The negative regulation of mitosis by wee1+ likely involves protein phosphorylation.
    • Wee1+ and cdc25+ form a regulatory system controlling cdc2+ activity and mitotic initiation.

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