Abstract
Condensin, a central player in eukaryotic chromosomal dynamics, contains five evolutionarily-conserved subunits. Two SMC (structural maintenance of chromosomes) subunits contain ATPase, hinge, and coiled-coil domains. One non-SMC subunit is similar to bacterial kleisin, and two other non-SMC subunits contain HEAT (similar to armadillo) repeats. Here we report isolation and characterization of 21 fission yeast (Schizosaccharomyces pombe) mutants for three non-SMC subunits, created using error-prone mutagenesis that resulted in single-amino acid substitutions. Beside condensation, segregation, and DNA repair defects, similar to those observed in previously isolated SMC and cnd2 mutants, novel phenotypes were observed for mutants of HEAT-repeats containing Cnd1 and Cnd3 subunits. cnd3-L269P is hypersensitive to the microtubule poison, thiabendazole, revealing defects in kinetochore/centromere and spindle assembly checkpoints. Three cnd1 and three cnd3 mutants increased cell size and doubled DNA content, thereby eliminating the haploid state. Five of these mutations reside in helix B of HEAT repeats. Two non-SMC condensin subunits, Cnd1 and Cnd3, are thus implicated in ploidy maintenance.
Highlights
Condensin plays a major role in chromosome dynamics during mitosis, interphase, and development [1,2,3,4]
It is essential for chromosome condensation and segregation in diverse organisms, from bacteria and fungi, such as budding yeast and fission yeast, to flies and humans [5,6,7,8,9,10,11,12,13,14,15]
Cut14-Y1 and cnd2-1 were sensitive to DNA damage [16, 17]
Summary
Condensin plays a major role in chromosome dynamics during mitosis, interphase, and development [1,2,3,4]. It is essential for chromosome condensation and segregation in diverse organisms, from bacteria and fungi, such as budding yeast and fission yeast, to flies and humans [5,6,7,8,9,10,11,12,13,14,15]. Condensin contains five essential subunits that are conserved in eukaryotes.
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