title: Fission yeast genes which disrupt mitotic chromosome segregation when overexpressed.
abstract: An interference assay has been devised in Schizosaccharomyces pombe to rapidly identify and clone genes involved in chromosome segregation. Random S.pombe cDNAs were overexpressed from an inducible promoter in a strain carrying an additional, non-essential minichromosome. Overexpression of cDNAs derived from four genes, two known (nda3+and ubc4+, encoding beta-tubulin and a ubiquitin conjugating enzyme, respectively) and two unknown, named mlo2+ and mlo3+ (missegregation & lethal when over expressed) caused phenotypes consistent with a failure to segregate chromosomes. Full overexpression of all four cDNAs was lethal. Cells overexpressing nda3+ and ubc4+ cDNAs arrested with condensed unsegregated chromosomes and cells overexpressing mlo2+ displayed an asymmetric distribution of nuclear chromatin. Sublethal levels of overexpression of nda3+, ubc4+ and mlo2+ cDNAs caused elevated rates of minichromosome loss. A third cDNA mlo3+, displayed no increase in the frequency of minichromosome loss at sublethal levels of overexpression but full overexpression caused a complete failure to segregate chromosomes. Our results confirm the assumption that beta-tubulin overexpression is lethal in S.pombe, implicate ubc4+ in the control of metaphase-anaphase transition in fission yeast and finally identify two new genes, mlo2+and mlo3+, likely to play an important role for chromosome transmission fidelity in mitosis.
authors.affiliation: M.R.C. Human Genetics Unit, Western General Hospital, Edinburgh, UK. jpaul.javerzat@ibgc.u-bordeaux2.fr
authors.forename: J P
authors.initials: JP
authors.lastname: Javerzat
authors.forename: G
authors.initials: G
authors.lastname: Cranston
authors.forename: R C
authors.initials: RC
authors.lastname: Allshire
mesh_terms: D015825:Chromosomes, Fungal / Q000502:physiology*; D018076:DNA, Complementary / Q000235:genetics; D004271:DNA, Fungal / Q000235:genetics; D015870:Gene Expression; D005800:Genes, Fungal; D005804:Genes, Lethal; D008025:Ligases / Q000235:genetics; D008856:Microscopy, Fluorescence; D008938:Mitosis / Q000235:genetics*; D008969:Molecular Sequence Data; D010641:Phenotype; D011401:Promoter Regions, Genetic; D012568:Schizosaccharomyces / Q000235:genetics*; D014170:Transformation, Genetic; D014404:Tubulin / Q000235:genetics; D044763:Ubiquitin-Conjugating Enzymes
chemical_list: D018076:DNA, Complementary; D004271:DNA, Fungal; D014404:Tubulin; D044763:Ubiquitin-Conjugating Enzymes; C063109:ubiquitin-conjugating enzyme UBC4; D008025:Ligases