Natarajan Shobhana, Nickles Kristy, McEachern Michael J
Department of Genetics, Fred C. Davison Life Sciences Complex, Athens, GA 30602, USA.
FEMS Yeast Res. 2006 May;6(3):442-8. doi: 10.1111/j.1567-1364.2005.00042.x.
Both subtelomeric and telomeric recombination events can be greatly enhanced in Kluyveromyces lactis mutants lacking telomerase and having abnormally short telomeres. In this study, we utilized cells containing a single telomere composed of mutant repeats carrying a phenotypically silent mutation to test whether the exchange of telomeric repeats was a frequent event in mitotic and meiotic wild-type K. lactis cells. Amongst more than 100 subclones followed during multiple passages of mitotic growth, one instance of a terminal duplication extending into a subtelomeric sequence was observed, but no occurrences of intertelomeric recombination were found. This suggests that intertelomeric recombination is not an important contributor to telomere maintenance in normal K. lactis cells. Rare recombination events resulting in the replacement of a subtelomeric marker with a sequence from another chromosome end also led to the replacement of the telomeric repeat tract. This is consistent with these events being a result of break-induced replication. Movement of a subtelomeric or telomeric sequence from one chromosome end to another was not observed in haploid cells derived from mating and sporulation. This suggests that the exchange of telomeric repeats is not a routine occurrence in K. lactis meiosis.
在缺乏端粒酶且端粒异常短的乳酸克鲁维酵母突变体中，亚端粒和端粒重组事件均可显著增强。在本研究中，我们利用含有由携带表型沉默突变的突变重复序列组成的单个端粒的细胞，来测试端粒重复序列的交换在有丝分裂和减数分裂的野生型乳酸克鲁维酵母细胞中是否是常见事件。在有丝分裂生长的多次传代过程中追踪的100多个亚克隆中，观察到一个延伸至亚端粒序列的末端重复实例，但未发现端粒间重组事件。这表明端粒间重组并非正常乳酸克鲁维酵母细胞中端粒维持的重要因素。罕见的重组事件导致亚端粒标记被来自另一个染色体末端的序列取代，这也导致了端粒重复序列的替换。这与这些事件是断裂诱导复制的结果一致。在由交配和孢子形成产生的单倍体细胞中未观察到亚端粒或端粒序列从一个染色体末端移动到另一个染色体末端。这表明端粒重复序列的交换在乳酸克鲁维酵母减数分裂中并非常规事件。
