Telomerase Recruitment in Saccharomyces Cerevisiae is not Dependent on Tel1-mediated Phosphorylation of Cdc13

Funding Source

National Institutes of Health, F. M. Kirby Foundation, G. Harold and Leila Y. Mathers Charitable Foundation.

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Department of Chemistry

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In Saccharomyces cerevisiae, association between the Est1 telomerase subunit and the telomere-binding protein Cdc13 is essential for telomerase to be recruited to its site of action. A current model proposes that Tel1 binding to telomeres marks them for elongation, as the result of phosphorylation of a proposed S/TQ cluster in the telomerase recruitment domain of Cdc13. However, three observations presented here argue against one key aspect of this model. First, the pattern of Cdc13 phosphatase-sensitive isoforms is not altered by loss of Tel1 function or by mutations introduced into two conserved serines (S249 and S255) in the Cdc13 recruitment domain. Second, an interaction between Cdc13 and Est1, as monitored by a two-hybrid assay, is dependent on S255 but Tel1-independent. Finally, a derivative of Cdc13, cdc13-(S/TQ) 11→(S/TA)11, in which every potential consensus phosphorylation site for Tel1 has been eliminated, confers nearly wild-type telomere length. These results are inconsistent with a model in which the Cdc13-Est1 interaction is regulated by Tel1-mediated phosphorylation of the Cdc13 telomerase recruitment domain. We propose an alternative model for the role of Tel1 in telomere homeostasis, which is based on the assumption that Tel1 performs the same molecular task at double-strand breaks (DSBs) and chromosome termini.


DOI: 10.1534/genetics.110.122044

PubMed ID: 20837994


We thank members of the Lundblad lab, Titia de Lange and Reuben Shaw for useful discussions during the course of this work, David Shore for strains, and Erin Ford and Leslie Ricks for technical assistance. This research was supported by a postdoctoral fellowship DAMD 17-02-1-0276 (to R.B.C), by grant GM55867 from the National Institutes of Health, and by funding from the F. M. Kirby Foundation and the G. Harold and Leila Y. Mathers Charitable Foundation.