Xu Xingya, Nakazawa Norihiko, Yanagida Mitsuhiro
Okinawa Institute of Science and Technology Graduate University, Onna-son, Okinawa, Japan; Department of Genetics, Graduate School of Medicine, Osaka University, Suita, Osaka, Japan.
Okinawa Institute of Science and Technology Graduate University, Onna-son, Okinawa, Japan.
PLoS One. 2015 Mar 12;10(3):e0119347. doi: 10.1371/journal.pone.0119347. eCollection 2015.
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.
凝缩蛋白是真核生物染色体动力学的核心参与者，由五个进化上保守的亚基组成。两个SMC（染色体结构维持）亚基包含ATP酶、铰链和卷曲螺旋结构域。一个非SMC亚基类似于细菌kleisin，另外两个非SMC亚基包含HEAT（类似于犰狳）重复序列。在此，我们报告了利用易错诱变产生单氨基酸取代，从而分离和鉴定了21个裂殖酵母（粟酒裂殖酵母）三个非SMC亚基的突变体。除了出现与先前分离的SMC和cnd2突变体中观察到的类似的凝缩、分离和DNA修复缺陷外，还观察到含有Cnd1和Cnd3亚基的HEAT重复序列突变体的新表型。cnd3-L269P对微管毒素噻苯咪唑高度敏感，揭示了动粒/着丝粒和纺锤体组装检查点的缺陷。三个cnd1和三个cnd3突变体增加了细胞大小并使DNA含量加倍，从而消除了单倍体状态。这些突变中有五个位于HEAT重复序列的螺旋B中。因此，两个非SMC凝缩蛋白亚基Cnd1和Cnd3与倍性维持有关。
