1. ¹The State Key Laboratory of Molecular Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, The Graduate School of Chinese Academy of Sciences, Shanghai 200031, China
2. ²Department of Biochemistry, School of Medicine, Nantong University, Nantong, Jiangsu 226001, China
3. ³Institute for Biopharmaceutical Science, National Yang-Ming University, Shih-Pai, 112, Taipei, Taiwan

Correspondence: Jin-Qiu Zhou, Tel: 86-21-54921076; E-mail: jqzhou@sibs.ac.cn

Received 6 October 2008; Revised 11 January 2009; Accepted 15 February 2009.

Abstract

In Saccharomyces cerevisiae, the essential gene CDC13 encodes a telomeric single-stranded DNA-binding protein that interacts with Stn1p and Ten1p genetically and physically, and is required for telomere end protection and telomere length control. The molecular mechanism by which Ten1 participates in telomere length regulation and chromosome end protection remains elusive. In this work, we observed a weak interaction of Cdc13p and Ten1p in a gel-filtration analysis using purified recombinant Cdc13p and Ten1p. Ten1p itself exhibits a weak DNA-binding activity, but enhances the telomeric TG_1–3 DNA-binding ability of Cdc13p. Cdc13p is co-immunoprecipitated with Ten1p. In the mutant ten1-55 or ten1-66 cells, the impaired interaction between Ten1p and Cdc13p results in much longer telomeres, as well as a decreased association of Cdc13p with telomeric DNA. Consistently, the Ten1-55 and Ten1-66 mutant proteins fail to stimulate the telomeric DNA-binding activity of Cdc13p in vitro. These results suggest that Ten1p enhances the telomeric DNA-binding activity of Cdc13p to negatively regulate telomere length.