Suppression of a mitotic mutant by tRNA-Ala anticodon mutations that produce a dominant defect in late mitosis.
Cold-sensitive dominant mutants scn1 and scn2 of Schizosaccharomyces pombe were isolated by their ability to suppress temperature-sensitive cut9-665 defective in an essential subunit (human Apc6/budding yeast Cdc16 ortholog) of anaphase promoting complex/cyclosome (APC/C). APC/C mutants were defective in metaphase/anaphase transition, whereas single scn mutants showed the delay in anaphase spindle elongation at 20 degrees C. The scn mutants lost viability because of chromosome missegregation, and were sensitive to a tubulin poison. To understand the scn phenotypes, mutant genes were identified. Surprisingly, scn1 and scn2 have the same substitution in the anticodon of two different tRNA-Ala (UGC) genes. UGC was altered to UGU so that the binding of the tRNA-Ala to the ACA Thr codon in mRNA became possible. As cut9-665 contained an Ala535Thr substitution, wild-type Cut9 protein was probably produced in scn mutants. Indeed, plasmid carrying tRNA-Ala (UGU) conferred cold-sensitivity to wild-type and suppressed cut9-665 in a dominant fashion. The previously identified scn1(+) (renamed as scn3(+)) turned out to be a high copy suppressor for scn1 and scn2. These are the first tRNA mutants that cause a mitotic defect.
Kimata
Yuu
Y
Department of Gene Mechanisms, Graduate School of Biostudies, Kyoto University. Kitashirakawa-Oiwakecho, Sakyo-ku, Kyoto 606-8501, Japan.
Yanagida
Mitsuhiro
M
D000705:Anaphase; D000926:Anticodon / Q000235:genetics*; D002455:Cell Division; D002467:Cell Nucleus / Q000378:metabolism; D002470:Cell Survival; D016213:Cyclins / Q000378:metabolism; D003513:Cycloheximide / Q000494:pharmacology; D005799:Genes, Dominant / Q000235:genetics*; D008938:Mitosis / Q000235:genetics*; D009154:Mutation / Q000235:genetics*; D010641:Phenotype; D012344:RNA, Transfer, Ala / Q000235:genetics*; D012568:Schizosaccharomyces / Q000166:cytology / Q000235:genetics* / Q000378:metabolism; D029702:Schizosaccharomyces pombe Proteins / Q000235:genetics / Q000378:metabolism; D008941:Spindle Apparatus / Q000502:physiology; D013489:Suppression, Genetic / Q000235:genetics*; D013827:Thiabendazole / Q000494:pharmacology
D000926:Anticodon; D016213:Cyclins; D012344:RNA, Transfer, Ala; C091044:SCN1 protein, S pombe; D029702:Schizosaccharomyces pombe Proteins; D003513:Cycloheximide; D013827:Thiabendazole