Role of the ABC transporter Ste6 in cell fusion during yeast conjugation
Role of the ABC transporter Ste6 in cell fusion during yeast conjugation
复制标题
DOI：
10.1083/jcb.135.3.741
复制
发表时间：
1996-11-01
影响因子：
7.8
通讯作者：
Marsh, L
中科院分区：
文献类型：
--
作者：
Elia, L;Marsh, L
虽然酵母接合的早期阶段是很好地模仿处理信息素，最终降解的细胞壁和膜融合的交配，导致细胞质混合可能需要单独的信号。在多组分筛选中鉴定了在酿酒酵母交配过程中阻断细胞融合的突变。三个最紧密的突变被证明是ABC转运蛋白基因STE 6的部分功能等位基因，该基因是转运a因子所需的。回收ste 6（cef 1 -1）等位基因并测序。ste 6（cef 1 -1）等位基因含有终止密码子，预测其在氨基酸残基862（of 1290）处截短Ste 6。ste 6（cef）突变减少，但没有消除，a-因子的表达。光学和电子显微镜显示，不像ste 6无效突变，阻止交配前形成交配对，ste 6（cef）（细胞融合）等位基因允许交配的早期步骤正常进行，但在接合的晚期阶段，交配伴侣被一个单一的细胞壁包裹，只有一层薄薄的细胞壁材料分开，我们称之为融合壁。在形态学上，前合子出现对称，在细胞接触区域的外围具有成功的细胞壁融合。在交配条件下，对a因子的反应在伴侣细胞中被有效诱导，正如预期的那样，前合子的外观对称。表达ste 6（K1093 A）突变的菌株赋予比ste 6（cef）高两倍至四倍的a因子水平的出口，其在交配期间不积累前合子，这可以指示交配所需的a因子信号传导的严格阈值。然而，与对a因子敏感性大大增加的sst 2配偶体交配并不能抑制ste 6（cef）菌株的融合缺陷。α-因子结构基因的过表达也不能抑制融合缺陷，可能α-因子或STE 6在细胞融合中发挥更复杂的作用。
Though early stages of yeast conjugation are well-mimicked by treatment with pheromones, the final degradation of the cell wall and membrane fusion of mating that leads to cytoplasmic mixing may require separate signals. Mutations that blocked cell fusion during mating in Saccharomyces cerevisiae were identified in a multipartite screen. The three tightest mutations proved to be partial-function alleles of the ABC-transporter gene STE6 required for transport of a-factor. The ste6(cef1-1) allele was recovered and sequenced. The ste6(cef1-1) allele contained a stop codon predicted to truncate Ste6 at amino acid residue 862 (of 1290). The ste6(cef) mutations reduced, but did not eliminate, expression of a-factor. Light and electron microscopy revealed that unlike ste6 null mutations which block mating before the formation of mating pairs, the ste6(cef) (cell fusion) alleles permitted early steps in mating to proceed normally but blocked at a late stage in conjugation where mating partners were encased by a single cell wall and separated by only a thin layer of cell wall material we term the fusion wall. Morphologically the prezygotes appeared symmetrical with successful cell wall fusion at the periphery of the region of cell contact. Responses to a-factor were efficiently induced in partner cells under mating conditions as expected given the symmetric appearance of the prezygotes. A strain expressing a ste6(K1093A) mutation that conferred export of a twofold to fourfold higher level of a-factor than ste6(cef) did not accumulate prezygotes during mating which could indicate a tight threshold of a-factor signaling required for mating. However, mating to an sst2 partner which has a greatly increased sensitivity to a-factor did not suppress the fusion defect of a ste6(cef) strain. Overexpression of the structural gene for a-factor also did not suppress the fusion defect, It is possible that a-factor or STE6 play more complex roles in cell fusion.