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Molecular and Cellular Biology, November 2004, p. 9557-9567, Vol. 24, No. 21
0270-7306/04/$08.00+0 DOI: 10.1128/MCB.24.21.9557-9567.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.
Tatsuya Kibe,1
Ho-Young Kang,2
Yeon-Soo Seo,2
Masahiro Uritani,1
Takashi Ushimaru,3 and
Masaru Ueno1*
Department of Chemistry,1 Department of Biology, Shizuoka University, Shizuoka, Japan,3 Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Yusung-Ku, Daejeon, South Korea2
Received 22 April 2004/ Returned for modification 18 May 2004/ Accepted 11 August 2004
It has been suggested that the Schizosaccharomyces pombe Rad50 (Rad50-Rad32-Nbs1) complex is required for the resection of the C-rich strand at telomere ends in taz1-d cells. However, the nuclease-deficient Rad32-D25A mutant can still resect the C-rich strand, suggesting the existence of a nuclease that resects the C-rich strand. Here, we demonstrate that a taz1-d dna2-2C double mutant lost the G-rich overhang at a semipermissive temperature. The amount of G-rich overhang in S phase in the dna2-C2 mutant was lower than that in wild-type cells at the semipermissive temperature. Dna2 bound to telomere DNA in a chromatin immunoprecipitation assay. Moreover, telomere length decreased with each generation after shift of the dna2-2C mutant to the semipermissive temperature. These results suggest that Dna2 is involved in the generation of G-rich overhangs in both wild-type cells and taz1-d cells. The dna2-C2 mutant was not gamma ray sensitive at the semipermissive temperature, suggesting that the ability to process double-strand break (DSB) ends was not affected in the dna2-C2 mutant. Our results reveal that DSB ends and telomere ends are processed by different mechanisms.
Present address: Telomere Biology Laboratory, Cancer Research UK, London EC2A 3PX, United Kingdom.
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