Copy number sequencing in S. cerevisiae

We asked whether origin firing is linked to telomere length regulation in S. cerevisiae. To test this, we collected genomic DNA from G1 phase cells and S phase cells for several genotypes and carried out whole genome sequencing. We used the sequence read counts to determine which areas of the genome had increased their copy number in early S phase compared to G1. We examined wildtype and different mutant strains and determined which previously identified origins had fired. We found that mutant strains that showed increased origin firing did not show longer telomeres. We conclude that origin firing is not linked to telomere length regulation and that the Rif1 protein has two distinct, separable roles in the regulation of and telomere length and the regulation of origin firing.

本研究旨在探究酿酒酵母（Saccharomyces cerevisiae）中复制起始激活（origin firing）是否与端粒长度调控存在关联。为验证上述假设，我们针对多种基因型的细胞，分别收集G1期与S期的基因组DNA，并开展全基因组测序（whole genome sequencing）。我们借助测序读段计数（sequence read counts），以G1期细胞为对照，鉴定出早期S期基因组中拷贝数发生扩增的区域。我们对野生型菌株与不同突变菌株进行分析，明确了此前已鉴定的复制起始位点的激活状态。研究结果显示，复制起始激活程度升高的突变菌株，其端粒长度并未出现延长。综上，我们得出结论：复制起始激活与端粒长度调控并无关联，且Rif1蛋白在端粒长度调控与复制起始激活调控中发挥着两种独立且可分离的功能。