A genome–wide screen to identify genes controlling the rate of entry into mitosis in fission yeast

We have carried out a haploinsufficiency (HI) screen in fission yeast using heterozygous deletion diploid mutants of a genome-wide set of cell cycle genes to identify genes encoding products whose level determines the rate of progression through the cell cycle. Cell size at division was used as a measure of advancement or delay of the G2-M transition of rod-shaped fission yeast cells. We found that 13 mutants were significantly longer or shorter (greater than 10%) than control cells at cell division. These included mutants of the <i>cdc2, cdc25, wee1</i> and <i>pom1</i> genes, which have previously been shown to play a role in the timing of entry into mitosis, and which validate this approach. Seven of these genes are involved in regulation of the G2-M transition, 5 for nuclear transport and one for nucleotide metabolism. In addition we identified 4 more genes that were 8–10% longer or shorter than the control that also had roles in regulation of the G2-M transition or in nuclear transport. The genes identified here are all conserved in human cells, suggesting that this dataset will be useful as a basis for further studies to identify rate-limiting steps for progression through the cell cycle in other eukaryotes.

本研究以裂殖酵母（fission yeast）为实验模型，利用针对全基因组细胞周期基因集构建的杂合缺失二倍体突变体开展单倍体不足（haploinsufficiency, HI）筛选，以鉴定产物表达水平决定细胞周期进程速率的基因。本研究以杆状裂殖酵母细胞分裂时的体积，作为衡量其G2-M期转换（G2-M transition）提前或延迟的指标。结果显示，13株突变体在细胞分裂时的体积与对照细胞相比存在显著差异（偏差超过10%），表现为体积更长或更短。其中包含cdc2、cdc25、wee1及pom1基因的突变体，这些基因此前已被证实参与有丝分裂进入的时序调控，同时也验证了本筛选方法的可靠性。在这13个差异突变基因中，7个参与G2-M期转换的调控，5个参与核运输（nuclear transport），1个参与核苷酸代谢（nucleotide metabolism）。此外，本研究还鉴定出4个与对照相比体积偏差为8%~10%的基因，这些基因同样参与G2-M期转换调控或核运输过程。本研究鉴定的所有基因在人类细胞中均存在保守同源序列，表明该数据集可作为后续研究的基础，用于鉴定其他真核生物细胞周期进程中的限速步骤。