Niwa O, Matsumoto T, Chikashige Y, Yanagida M
Department of Biophysics, Faculty of Science, Kyoto University, Japan.
EMBO J. 1989 Oct;8(10):3045-52. doi: 10.1002/j.1460-2075.1989.tb08455.x.
A 530 kb long Schizosaccharomyces pombe linear minichromosome, Ch16, containing a centric region of chromosome III, has previously been made. In the present study, we constructed a number of deletions in the right and/or left arms of Ch16, and compared their structure and behaviour with Ch16. The functional centromere, cen3, is allocated within a 120 kb long region which is covered by the shortest derivative, Ch10, and is comprised mostly of centromeric repeating sequences. The shortest minichromosome is stable in mitosis and the copy number control is apparently precise. In monosomic meiosis it segregates normally. In disomic meioses, however, the frequency of non-disjunction is very high, suggesting that it may not form a pair. The mitotic loss rate of one of the left-arm deletions, ChR32, which lacks a part of the centromeric repeating sequence, is the highest of all the deletions. This deletion also exhibits the highest precocious sister chromatid separation in meiosis I, suggesting that sister chromatid association might become weakened in ChR32. Our results indicate that the proper meiotic segregation of S.pombe minichromosomes is dependent upon the formation of a bivalent. S.pombe may not have the 'distributive segregation' found with Saccharomyces cerevisiae minichromosomes.
此前已构建出一种530 kb长的粟酒裂殖酵母线性微型染色体Ch16，它包含第三条染色体的着丝粒区域。在本研究中，我们在Ch16的右臂和/或左臂构建了多个缺失片段，并将它们的结构和行为与Ch16进行比较。功能性着丝粒cen3位于一个120 kb长的区域内，该区域被最短的衍生染色体Ch10覆盖，且主要由着丝粒重复序列组成。最短的微型染色体在有丝分裂中是稳定的，拷贝数控制显然很精确。在单体减数分裂中它正常分离。然而，在二体减数分裂中，不分离的频率非常高，这表明它可能无法形成配对。左臂缺失片段之一ChR32缺少部分着丝粒重复序列，其有丝分裂丢失率在所有缺失片段中是最高的。该缺失片段在减数分裂I中还表现出最高的早熟姐妹染色单体分离，这表明在ChR32中姐妹染色单体的关联可能会变弱。我们的结果表明，粟酒裂殖酵母微型染色体的正常减数分裂分离依赖于二价体的形成。粟酒裂殖酵母可能没有酿酒酵母微型染色体中发现的“分布式分离”。
