Genetic determinants of spindle pole body duplication in budding yeast.
Genetic determinants of spindle pole body duplication in budding yeast.
复制标题
芽殖酵母纺锤体极体复制的遗传决定因素。
DOI：
10.1101/sqb.1991.056.01.079
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发表时间：
1991
期刊：
影响因子：
--
通讯作者：
Byers,B
中科院分区：
文献类型：
--
作者：
Winey,M;Baum,P;Goetsch,L;Byers,B
真核细胞周期中的一个关键功能是形成两极有丝分裂纺锤体。这一复杂的过程反过来又依赖于中心体的复制，中心体产生于每个子细胞从前一次有丝分裂中继承的单一纺锤体极。这种重复的性质及其调节模式仍然有些模糊，因为中心体通常只能被识别为非晶态材料的模糊阵列，大多数微管似乎是从该阵列发出的。在动物细胞中，位于中心体核心内的中心粒为中心体的分布提供了一个独特的标记(Mclntosh 1983)，但围绕它们的分散排列的中心体物质的确切行为很难具体说明。相比之下，酵母和其他真菌中的类似物质看起来像一个离散的细胞器--纺锤体(SPB)--其复制模式更容易被识别(Byers和Goetsch 1975)。酿酒酵母的SPB是嵌入核膜中的深色染色物质的多层圆盘，在那里它是来自其核面和细胞质面的微管的组装场所(Moens和Rapport 1971)。半桥是一种独特的双层结构，它似乎代表了核膜的一段修饰，毗邻SPB的一侧，似乎在SPB的复制中发挥了重要作用。复制的初始阶段是通过卫星出现在半桥的外表面来表示的；这个小结构似乎是由类似于SPB本身的材料制成的。虽然没有检测到其他中间阶段，但SPB的复制似乎需要卫星的扩张和它在核包膜中的插入，从而将半桥转变为完整的桥。一旦将SPB插入囊膜，其核表面就会出现微管。在后来的阶段，桥被切断，随着纺锤体的形成，SPBS经历彼此分离。许多CDC突变导致停滞状态，其中SPB复制周期与细胞分裂周期的其他方面保持良好的协调(Byers和Goetsch，1974)。然而，其他工作表明，在CDC突变中，cdc31在解偶联这些过程、抑制卫星形成和SPB复制方面是独一无二的，但不能抑制芽形成或染色体DNA复制。这使突变细胞进入导致单极有丝分裂的状态；染色体都传递到唯一的功能极，导致一个子细胞多倍化，在返回允许的条件下存活下来。因此，极点复制失败先于卫星编队失败这一事实支持这样一种观点，即卫星是新生的小岛屿发展中国家的前身。Karl基因的条件致死性也有类似的表型，它最初是通过它在核配子中的作用来确定的，但也被认为在SPB复制周期中起着直接作用(Rose和Fink，1987)。我们致力于更深入地研究CDC31及其相关基因的功能。克隆和序列分析表明，CDC31是钙调素样钙结合蛋白家族的成员(Baum等人)。1986)，提示CDC31的功能可能是由钙离子的瞬时释放触发的。对温度敏感等位基因的执行点分析表明，如果要在下一个细胞周期中正常发生SPB复制，在一个细胞周期接近结束时存在一个功能关键期(数据未显示)。由于卫星形成本身从未见过发生在细胞周期开始之前，我们假设…
A key function in the eukaryotic cell cycle is the formation of the bipolar mitotic spindle. This complex process depends in turn on duplication of the centrosome, which arises from the single spindle pole inherited by each daughter cell from the preceding mitotic division. The nature of this duplication and its mode of regulation remain somewhat obscure, for the centrosome usually is identifiable only as a poorly defined array of amorphous material from which the majority of microtubules appear to emanate. In animal cells, the centrioles that lie within the core of the centrosome provide a distinctive marker for centrosomal distribution (Mclntosh 1983), but the precise behavior of the diffusely arrayed centrosomal material that surrounds them is difficult to specify. In contrast, the analogous material in yeast and other fungi appears as a discrete organelle--the spindle pole body (SPB)--whose pattern of duplication can be recognized more readily (Byers and Goetsch 1975). The SPB of Saccharomyces cerevisiae is a multilayered disk of darkly staining material embedded in the nuclear envelope, where it serves as a site for the assembly of microtubules from both its nuclear and cytoplasmic faces (Moens and Rapport 1971). A distinctive bilaminar structure, the halfbridge, which appears to represent a modified segment of the nuclear envelope, abuts one edge of the SPB and seems to play a major role in SPB duplication. The initial phase of duplication is signaled by the appearance of the satellite on the outer surface of the halfbridge; this small structure appears to be of material similar to that of the SPB proper. Although no other intermediate stages have been detected, SPB duplication then seems to entail an expansion of the satellite and its insertion in the nuclear envelope, thus transforming the half-bridge into a complete bridge. Upon insertion of the SPB into the envelope, microtubules arise on its nuclear face. At a later stage, the bridge is severed and the SPBs undergo separation from one another as the spindle forms. Many cdc mutations cause states of arrest in which the SPB duplication cycle remains well coordinated with other aspects of the cell division cycle (Byers and Goetsch 1974). Other work has shown, however, that cdc31 is unique among cdc mutations in uncoupling these processes, inhibiting satellite formation and SPB duplication, but not bud formation or chromosomal DNA replication. This brings the mutant cell into a condition leading to monopolar mitosis; the chromosomes all pass to the sole functional pole, resulting in polyploidization of the one daughter cell surviving a return to permissive conditions. The fact that failure of pole duplication is thus preceded by failure of satellite formation supports the viewpoint that the satellite is a precursor of the nascent SPB. A similar phenotype has been demonstrated for conditional lethality in the KARl gene, which was originally identified by its role in karyogamy but is also known to play a direct role in the SPB duplication cycle (Rose and Fink 1987). We have undertaken to explore the functions of CDC31 and related genes more thoroughly. Cloning and sequence analysis have revealed that Cdc31 is a member of the family of calmodulin-like calcium-binding proteins (Baum et al. 1986), suggesting that CDC31 function may be triggered by a transient release of calcium ions. Execution point analysis of the temperature-sensitive alleles has indicated that there is a critical period for function near the close of one cell cycle if SPB duplication is to occur normally in the next cycle (data not shown). Since satellite formation per se is never seen to occur before the beginning of the cell cycle, we postulate that …