Nucleic Acids Research, 2001, Vol. 29, No. 6 1326-1333
© 2001 Oxford University Press
The dhp1+ gene, encoding a putative nuclear 5'
3' exoribonuclease, is required for proper chromosome segregation in fission yeast
1Department of Molecular Biology, Institute of Medical Science, University of Tokyo, 4-6-1, Shirokanedai, Minato-ku, Tokyo 108-8639, Japan, 2Department of Biology, Graduate School of Science, Kyushu University, Fukuoka 812-8581, Japan, 3PRESTO, Japan Science and Technology Corporation, Fukuoka 812-8581, Japan and 4Microbial Chemistry, Center for Basic Research, The Kitasato Institute, Tokyo 108-8642, Japan
The Schizosaccharomyces pombe dhp1+ gene is an ortholog of the Saccharomyces cerevisiae RAT1 gene, which encodes a nuclear 5'
3' exoribonuclease, and is essential for cell viability. To clarify the cellular functions of the nuclear 5'3' exoribonuclease, we isolated and characterized a temperature-sensitive mutant of dhp1 (dhp1-1 mutant). The dhp1-1 mutant showed nuclear accumulation of poly(A)+ RNA at the restrictive temperature, as was already reported for the rat1 mutant. Interestingly, the dhp1-1 mutant exhibited aberrant chromosome segregation at the restrictive temperature. The dhp1-1 cells frequently contained condensed chromosomes, most of whose sister chromatids failed to separate during mitosis despite normal mitotic spindle elongation. Finally, chromosomes were displaced or unequally segregated. As similar mitotic defects were also observed in Dhp1p-depleted cells, we concluded that dhp1+ is required for proper chromosome segregation as well as for poly(A)+ RNA metabolism in fission yeast. Furthermore, we isolated a multicopy suppressor of the dhp1-1 mutant, referred to as din1+. We found that the gene product of dhp1-1 was unstable at high temperatures, but that reduced levels of Dhp1-1p could be suppressed by overexpressing Din1p at the restrictive temperature. Thus, Din1p may physically interact with Dhp1p and stabilize Dhp1p and/or restore its activity.
* To whom correspondence should be addressed. Tel: +81 3 5449 5517; Fax: +81 3 5449 5422; Email: tategone{at}ims.u-tokyo.ac.jp Present addresses: Takeo Shobuike, Department of Microbiology, Saga Medical School, Saga 849-8501, Japan Shoji Sugano, Department of Plant Physiology, National Institute of Agribiological Resources, Ibaraki 305-8602, Japan
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