The role of Stn1p in Saccharomyces cerevisiae telomere capping can be separated from its interaction with Cdc13p.
The function of telomeres is twofold: to facilitate complete chromosome replication and to protect chromosome ends against fusions and illegitimate recombination. In the budding yeast Saccharomyces cerevisiae, interactions among Cdc13p, Stn1p, and Ten1p are thought to be critical for promoting these processes. We have identified distinct Stn1p domains that mediate interaction with either Ten1p or Cdc13p, allowing analysis of whether the interaction between Cdc13p and Stn1p is indeed essential for telomere capping or length regulation. Consistent with the model that the Stn1p essential function is to promote telomere end protection through Cdc13p, stn1 alleles that truncate the C-terminal 123 residues fail to interact with Cdc13p and do not support viability when expressed at endogenous levels. Remarkably, more extensive deletions that remove an additional 185 C-terminal residues from Stn1p now allow cell growth at endogenous expression levels. The viability of these stn1-t alleles improves with increasing expression level, indicating that increased stn1-t dosage can compensate for the loss of Cdc13p-Stn1p interaction. However, telomere length is misregulated at all expression levels. Thus, an amino-terminal region of Stn1p is sufficient for its essential function, while a central region of Stn1p either negatively regulates the STN1 essential function or destabilizes the mutant Stn1 protein.
Petreaca
Ruben C
RC
Cell, Molecular, and Developmental Biology Graduate Program, Department of Cell Biology and Neuroscience, University of California, Riverside, California 92506, USA.
Chiu
Huan-Chih
HC
Nugent
Constance I
CI
D000483:Alleles; D001665:Binding Sites / Q000235:genetics; D018797:Cell Cycle Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D002868:Chromosomal Proteins, Non-Histone / Q000235:genetics / Q000378:metabolism; D004249:DNA Damage; D004271:DNA, Fungal / Q000235:genetics / Q000378:metabolism; D005800:Genes, Fungal; D005816:Genetic Complementation Test; D009154:Mutation; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011995:Recombination, Genetic; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D019098:Telomerase / Q000235:genetics / Q000378:metabolism; D016615:Telomere / Q000235:genetics* / Q000378:metabolism*; D034501:Telomere-Binding Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*
C452219:Cdc13 protein, S cerevisiae; D018797:Cell Cycle Proteins; D002868:Chromosomal Proteins, Non-Histone; D004271:DNA, Fungal; D029701:Saccharomyces cerevisiae Proteins; C428109:Stn1 protein, S cerevisiae; C512860:TEN1 protein, S cerevisiae; D034501:Telomere-Binding Proteins; D019098:Telomerase