Lee I-Ju, Wang Ning, Hu Wen, Schott Kersey, Bähler Jürg, Giddings Thomas H, Pringle John R, Du Li-Lin, Wu Jian-Qiu
Graduate Program of Molecular, Cellular, and Developmental Biology, The Ohio State University, Columbus, OH 43210 Department of Molecular Genetics, The Ohio State University, Columbus, OH 43210.
Department of Molecular Genetics, The Ohio State University, Columbus, OH 43210.
Mol Biol Cell. 2014 Sep 15;25(18):2735-49. doi: 10.1091/mbc.E13-11-0699. Epub 2014 Jul 16.
Centrosomes play critical roles in the cell division cycle and ciliogenesis. Sfi1 is a centrin-binding protein conserved from yeast to humans. Budding yeast Sfi1 is essential for the initiation of spindle pole body (SPB; yeast centrosome) duplication. However, the recruitment and partitioning of Sfi1 to centrosomal structures have never been fully investigated in any organism, and the presumed importance of the conserved tryptophans in the internal repeats of Sfi1 remains untested. Here we report that in fission yeast, instead of doubling abruptly at the initiation of SPB duplication and remaining at a constant level thereafter, Sfi1 is gradually recruited to SPBs throughout the cell cycle. Like an sfi1Δ mutant, a Trp-to-Arg mutant (sfi1-M46) forms monopolar spindles and exhibits mitosis and cytokinesis defects. Sfi1-M46 protein associates preferentially with one of the two daughter SPBs during mitosis, resulting in a failure of new SPB assembly in the SPB receiving insufficient Sfi1. Although all five conserved tryptophans tested are involved in Sfi1 partitioning, the importance of the individual repeats in Sfi1 differs. In summary, our results reveal a link between the conserved tryptophans and Sfi1 partitioning and suggest a revision of the model for SPB assembly.
中心体在细胞分裂周期和纤毛发生过程中发挥着关键作用。Sfi1是一种从酵母到人类都保守的与中心蛋白结合的蛋白质。芽殖酵母中的Sfi1对于纺锤体极体(SPB;酵母中心体)复制的起始至关重要。然而,在任何生物体中,Sfi1向中心体结构的募集和分配从未得到充分研究,并且Sfi1内部重复序列中保守色氨酸的假定重要性仍未得到验证。在此我们报道,在裂殖酵母中,Sfi1并非在SPB复制起始时突然加倍并在之后保持恒定水平,而是在整个细胞周期中逐渐被募集到SPB。与sfi1Δ突变体一样,色氨酸到精氨酸的突变体(sfi1-M46)形成单极纺锤体并表现出有丝分裂和胞质分裂缺陷。Sfi1-M46蛋白在有丝分裂期间优先与两个子SPB之一结合,导致在接收不足Sfi1的SPB中无法进行新的SPB组装。尽管所测试的所有五个保守色氨酸都参与Sfi1的分配,但Sfi1中各个重复序列的重要性有所不同。总之,我们的结果揭示了保守色氨酸与Sfi1分配之间的联系,并建议对SPB组装模型进行修订。