Negative regulation of mitosis by wee1+, a gene encoding a protein kinase homolog

https://www.cell.com/cell/pdf/0092-8674(86)90546-5.pdf

cdc25+ functions as an inducer in the mitotic control of fission yeast.

The control regulating commitment to the cell division cycle of eukaryotes seems to occur before the initiation of DNA replication1–4. In the budding yeast Saccharomyces cerevisiae, this control is called start and is the earliest gene-controlled event of the cell cycle3–5. A haploid cell which has completed start is committed to cell division and unable to undergo alternative developmental fates such as conjugation. Here, we describe an analogous start control in the fission yeast Schizosaccharomyces pombe. We have tested the ability of cdc mutants blocked at various stages of the cell cycle to undergo conjugation. Only mutants of cdc 2 and cdc 10 which block during the G1 period are able to conjugate. Other mutants which block during G1, S phase, G2 or mitosis are committed to cell division and cannot conjugate. The commitment control start is located in G1, and its completion requires the gene functions of cdc 2 and 10. Completion of start occurs at the beginning of the cell cycle in rapidly growing cells, but is delayed to later in the cell cycle at slow growth rates. The cdc 2 gene function also participates in another major cell cycle control which determines the timing of mitosis6–8. Therefore cdc 2 is a cell cycle control gene which acts at two separate points in the cell cycle: it is required in G1 for commitment to cell division and in G2 for the control of mitosis.

Gene required in G1 for commitment to cell cycle and in G2 for control of mitosis in fission yeast.

The cell cycle control gene cdc2+ of fission yeast encodes a protein kinase potentially regulated by phosphorylation

The mating pheromone alpha-factor arrests Saccharomyces cerevisiae MATa cells in the G1 phase of the cell cycle. Size control is also exerted in G1, since cells do not exit G1 until they have attained a critical size. A dominant mutation (DAF1-1) which causes both alpha-factor resistance and small cell size (volume about 0.6-fold that of the wild type) has been isolated and characterized genetically and by molecular cloning. Several alpha-factor-induced mRNAs were induced equivalently in daf1+ and DAF1-1 cells. The DAF1-1 mutation consisted of a termination codon two-thirds of the way through the daf1+ coding sequence. A chromosomal deletion of DAF1 produced by gene transplacement increased cell volume about 1.5-fold; thus, DAF1-1 may be a hyperactive or deregulated allele of a nonessential gene involved in G1 size control. Multiple copies of DAF1-1 also greatly reduced the duration of the G1 phase of the cell cycle.

DAF1, a mutant gene affecting size control, pheromone arrest, and cell cycle kinetics of Saccharomyces cerevisiae.

The control co-ordinating cell division with cell growth has been investigated in the fission yeast Schizosaccharomyces pombe Twenty-five mutants altered in this control have been isolated which have the same growth rate as wild type but divide at a smaller cell size The mutants define two genes wee 1 and wee 2, both of which are involved in a control initiating mitosis when the cell attains a critical size

Mutants altered in the control co-ordinating cell division with cell growth in the fission yeast Schizosaccharomyces pombe.

The timing of individual nuclear gene replication during S phase in an eukaryote can now be studied by nitrosoguanidine mutagenesis. Using this technique, results also suggested that mitochondrial DNA replication is synchronous and a late event in the cell cycle.

Nitrosoguanidine mutagenesis during nuclear and mitochondrial gene replication

Synthesis of two DNA-dependent RNA polymerases in yeast.

http://www.biochemsoctrans.org/content/ppbiost/2/2/224.full.pdf

Bruce L. A. Carter

Papers

Mutants altered in the control co-ordinating cell division with cell growth in the fission yeast Schizosaccharomyces pombe.

Nitrosoguanidine mutagenesis during nuclear and mitochondrial gene replication

Synthesis of two DNA-dependent RNA polymerases in yeast.

The Timing of Mitochondrial Deoxyribonucleic Acid Replication during the Cell Cycle in Saccharomyces cerevisiae