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.