Jaspersen Sue L, Giddings Thomas H, Winey Mark
Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, CO 80309, USA.
J Cell Biol. 2002 Dec 23;159(6):945-56. doi: 10.1083/jcb.200208169. Epub 2002 Dec 16.
Accurate duplication of the Saccharomyces cerevisiae spindle pole body (SPB) is required for formation of a bipolar mitotic spindle. We identified mutants in SPB assembly by screening a temperature-sensitive collection of yeast for defects in SPB incorporation of a fluorescently marked integral SPB component, Spc42p. One SPB assembly mutant contained a mutation in a previously uncharacterized open reading frame that we call MPS3 (for monopolar spindle). mps3-1 mutants arrest in mitosis with monopolar spindles at the nonpermissive temperature, suggesting a defect in SPB duplication. Execution point experiments revealed that MPS3 function is required for the first step of SPB duplication in G1. Like cells containing mutations in two other genes required for this step of SPB duplication (CDC31 and KAR1), mps3-1 mutants arrest with a single unduplicated SPB that lacks an associated half-bridge. MPS3 encodes an essential integral membrane protein that localizes to the SPB half-bridge. Genetic interactions between MPS3 and CDC31 and binding of Cdc31p to Mps3p in vitro, as well as the fact that Cdc31p localization to the SPB is partially dependent on Mps3p function, suggest that one function for Mps3p during SPB duplication is to recruit Cdc31p, the yeast centrin homologue, to the half-bridge.
酿酒酵母纺锤体极体（SPB）的精确复制是形成双极有丝分裂纺锤体所必需的。我们通过筛选一组对温度敏感的酵母，以寻找荧光标记的完整SPB组件Spc42p在SPB整合中的缺陷，从而鉴定出SPB组装中的突变体。一个SPB组装突变体在一个以前未被鉴定的开放阅读框中发生了突变，我们将其称为MPS3（单极纺锤体）。mps3-1突变体在非允许温度下以单极纺锤体阻滞在有丝分裂期，这表明在SPB复制中存在缺陷。执行点实验表明，MPS3功能是G1期SPB复制第一步所必需的。与在SPB复制这一步所需的其他两个基因（CDC31和KAR1）中含有突变的细胞一样，mps3-1突变体阻滞时带有一个单一的未复制SPB，该SPB缺乏相关的半桥。MPS3编码一种必需的整合膜蛋白，定位于SPB半桥。MPS3与CDC31之间的遗传相互作用以及Cdc31p在体外与Mps3p的结合，以及Cdc31p在SPB上的定位部分依赖于Mps3p功能这一事实，表明Mps3p在SPB复制过程中的一个功能是将酵母中心蛋白同源物Cdc31p招募到半桥。
