Mouassite M, Camougrand N, Schwob E, Demaison G, Laclau M, Guérin M
Institut de Biochimie et Génétique Cellulaires du CNRS, Université Victor Segalen Bordeaux 2, 1 Rue Camille Saint-Saëns, 33077 Bordeaux, France.
Yeast. 2000 Jul;16(10):905-19. doi: 10.1002/1097-0061(200007)16:10<905::AID-YEA584>3.0.CO;2-1.
SUN4 is the fourth member of the SUN gene family from S. cerevisiae, whose products display high homology in their 258 amino acid C-terminal domain. SIM1, UTH1, NCA3 (the founding members) are involved in different cellular processes (DNA replication, ageing, mitochondrial biogenesis) and it is shown herein that SUN4 plays a role in the cell septation process. sun4 delta cells are larger than wild-type and begin a new cell cycle before they have separated from their mother cell. This phenotype is more pronounced in sun4Delta cells also deleted for UTH1. FACS analysis shows apparent polyploidy which disappears when the cell cycle is arrested by mating factor or nocodazole, indicating that cell septation is delayed without modification of the doubling time. Elutriated sun4 delta uth1 delta daughter cells are born larger, and therefore enter S phase sooner than their wild-type counterpart. S phase duration, as well as timing of Clb2 degradation, is normal, but cell septation is delayed. Sun4p/Scw3p was recently described as a cell wall protein (Cappellaro et al., 1998) and, consistent with this notion, electron micrographs of sun4 delta cells show defects in the final steps of cell wall septation. Our data suggest that Sun4p and Uth1p might contribute to the regulated process of cell wall morphogenesis and septation.
SUN4是酿酒酵母SUN基因家族的第四个成员，其产物在258个氨基酸的C端结构域中显示出高度同源性。SIM1、UTH1、NCA3（该家族的创始成员）参与不同的细胞过程（DNA复制、衰老、线粒体生物发生），本文表明SUN4在细胞分裂过程中发挥作用。sun4Δ细胞比野生型细胞大，并且在与母细胞分离之前就开始了新的细胞周期。这种表型在同时缺失UTH1的sun4Δ细胞中更为明显。流式细胞仪分析显示明显的多倍体现象，当细胞周期被交配因子或诺考达唑阻断时，这种现象消失，这表明细胞分裂延迟，但倍增时间没有改变。淘洗得到的sun4Δuth1Δ子细胞出生时更大，因此比野生型对应细胞更早进入S期。S期持续时间以及Clb2降解的时间是正常的，但细胞分裂延迟。Sun4p/Scw3p最近被描述为一种细胞壁蛋白（Cappellaro等人，1998年），与此观点一致，sun4Δ细胞的电子显微镜照片显示细胞壁分裂的最后步骤存在缺陷。我们的数据表明，Sun4p和Uth1p可能有助于细胞壁形态发生和分裂的调节过程。
