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Molecular and Cellular Biology, September 2000, p. 6399-6409, Vol. 20, No. 17
Division of Pharmacology, Biological Safety
Research Center, National Institute of Health Sciences, Setagaya-ku,
Tokyo 158-8501,1 Molecular Cell Biology
Laboratory, Graduate School of Pharmaceutical Sciences, Tohoku
University, Sendai, Miyagi 980-8578,2
Laboratory of Cellular and Molecular Biology, Institute of
Physical and Chemical Research (RIKEN), Wako, Saitama
351-0198,3 Department of Biological
Sciences, Graduate School of Sciences, University of Tokyo,
Bunkyo-ku, Tokyo 113-0033,4 Japan
Received 20 April 2000/Returned for modification 23 May
2000/Accepted 7 June 2000
The SGS1 gene of Saccharomyces cerevisiae
is a homologue for the Bloom's syndrome and Werner's syndrome genes.
The disruption of the SGS1 gene resulted in very poor
sporulation, and the majority of the cells were arrested at the
mononucleated stage. The recombination frequency measured by a
return-to-growth assay was reduced considerably in sgs1
disruptants. However, double-strand break formation, which is a key
event in the initiation of meiotic DNA recombination, occurred;
crossover and noncrossover products were observed in the disruptants,
although the amounts of these products were slightly decreased compared
with those in wild-type cells. The spores produced by sgs1
disruptants showed relatively high viability. The sgs1 spo13 double disruptants sporulated poorly, like the
sgs1 disruptants, but spore viability was reduced much more
than with either sgs1 or spo13 single
disruptants. Disruption of the RED1 or RAD17
gene partially alleviated the poor-sporulation phenotype of
sgs1 disruptants, indicating that portions of the
population of sgs1 disruptants are blocked by the meiotic
checkpoint. The poor sporulation of sgs1 disruptants was
complemented with a mutated SGS1 gene encoding a protein
lacking DNA helicase activity; however, the mutated gene could suppress
neither the sensitivity of sgs1 disruptants to methyl
methanesulfonate and hydroxyurea nor the mitotic hyperrecombination phenotype of sgs1 disruptants.
0270-7306/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Sgs1 Helicase Activity Is Required for Mitotic but
Apparently Not for Meiotic Functions
*
Corresponding author. Mailing address: Molecular Cell
Biology Laboratory, Graduate School of Pharmaceutical Sciences, Tohoku University, Aoba Aramaki, Aoba-ku, Sendai, Miyagi 980-8578, Japan. Phone: (81)-22-217-6874. Fax: (81)-22-217-6873. E-mail:
enomoto{at}mail.pharm.tohoku.ac.jp.
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