Carbon J, Clarke L
Department of Biological Sciences, University of California, Santa Barbara 93106.
New Biol. 1990 Jan;2(1):10-9.
Functional centromeric DNAs have now been isolated and characterized from both budding (Saccharomyces cerevisiae) and fission (Schizosaccharomyces pombe) yeasts. Artificial chromosomes containing these centromere DNA sequences segregate faithfully in both mitotic and meiotic cell divisions, but only in the parent organism. Structure-function analyses have revealed surprising fundamental differences between these two centromere classes. In the budding yeast centromeres, a 125-bp consensus DNA sequence contains all the information needed in cis to provide proper chromosome segregation. In contrast, the fission yeast centromeres each contain a long run (40 to 100 kb) of untranscribed repetitive DNA sequences arranged into a large inverted repeat, most of which is required for full centromere function. The fission yeast centromere-kinetochore appears to be a highly relevant experimental model for analysis of the mechanism of chromosome segregation in higher eukaryotes, in which the centromere regions often contain megabases of transcriptionally silent repetitive DNA sequences of unknown function.
目前，功能性着丝粒DNA已从芽殖酵母（酿酒酵母）和裂殖酵母（粟酒裂殖酵母）中分离并鉴定出来。含有这些着丝粒DNA序列的人工染色体在有丝分裂和减数分裂细胞分裂中都能忠实地分离，但仅在亲代生物体中如此。结构功能分析揭示了这两类着丝粒之间惊人的根本差异。在芽殖酵母着丝粒中，一个125 bp的共有DNA序列包含了顺式提供正确染色体分离所需的所有信息。相比之下，裂殖酵母着丝粒各自包含一段长的（40至100 kb）未转录的重复DNA序列，排列成一个大的反向重复序列，其中大部分是着丝粒完整功能所必需的。裂殖酵母着丝粒-动粒似乎是分析高等真核生物染色体分离机制的一个高度相关的实验模型，在高等真核生物中，着丝粒区域通常包含数百万碱基对的功能未知的转录沉默重复DNA序列。
