Exploring the mechanisms of telomerase regulation in Saccharomyces cerevisiae

Cells are the building blocks of all life forms; inside them is the organism's DNA, packaged tightly away in chromosomes. At the ends of each chromosome, there are special structures called telomeres. Telomeres protect the ends of each chromosome from degradation and fusion. However, telomeres shorten each time a cell divides. If telomeres reach a critically short length, the cell stops dividing and can undergo either senescence or apoptosis. A protective enzyme called telomerase is responsible for adding new telomeric sequence to overcome telomere shortening. Telomere dysfunction is associated with ageing, cancer, and other diseases. The focus of this thesis is the mechanism of telomerase recruitment and activation in the model organism Saccharomyces cerevisiae. The recruitment and activation of telomerase to the telomeres are key points of regulation, mediated by a complex set of interactions between telomere-associated proteins, telomeric DNA, and the RNA subunit of telomerase. One of the central proteins in this process is Cdc13, which binds to the single-stranded DNA overhang at the chromosome end. cdc13-2 is a well-characterized mutant allele of the gene, which changes amino acid 252 from glutamic acid to lysine. Telomerase is unable to elongate telomeres in this mutant, resulting in telomere shortening, replicative senescence, and ultimately cell death. In Chapters 2 and 3, we describe our unexpected finding that mutation of two additional genes, PIF1 and MEC1, can both independently, through separate mechanisms, suppress the cdc13-2 phenotype. Overall, my work further illustrates the complexity of telomerase regulation.

Dissertation: https://hdl.handle.net/11370/d69072dc-4f05-4cec-aadd-cf1a6727f13b