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Proc Natl Acad Sci U S A. 2011 Dec 20;108(51):20362-9. doi: 10.1073/pnas.1100281108. Epub 2011 Oct 3.

The telomeric Cdc13 protein interacts directly with the telomerase subunit Est1 to bring it to telomeric DNA ends in vitro.

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  • 1Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA.

Abstract

In Saccharomyces cerevisiae, a Cdc13-Est1 interaction is proposed to mediate recruitment of telomerase to DNA ends. Here we provide unique in vitro evidence for this model by demonstrating a direct interaction between purified Cdc13 and Est1. The Cdc13-Est1 interaction is specific and requires the in vivo defined Cdc13 recruitment domain. Moreover, in the absence of this interaction, Est1 is excluded from telomeric single-stranded (ss)DNA. The apparent association constand (K(d)) between Est1 and a Cdc13-telomeric ssDNA complex was ∼250 nM. In G2 phase cells, where telomerase is active, Cdc13 and Est1 were sufficiently abundant (∼420 and ∼110 copies per cell, respectively) to support complex formation. Interaction between Cdc13 and Est1 was unchanged by three telomerase-deficient mutations, Cdc13(E252K) (cdc13-2), Est1(K444E) (est1-60), and Cdc13(S249,255D), indicating that their telomerase null phenotypes are not due to loss of the Cdc13-Est1 interaction. These data recapitulate in vitro the first step in telomerase recruitment to telomeric ssDNA and suggest that this step is necessary to recruit telomerase to DNA ends.

PMID:
21969561
[PubMed - indexed for MEDLINE]
PMCID:
PMC3251085
Free PMC Article

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