Restriction of ectopic recombination by interhomolog interactions during Saccharomyces cerevisiae meiosis
Restriction of ectopic recombination by interhomolog interactions during Saccharomyces cerevisiae meiosis
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DOI：
10.1073/pnas.97.17.9537
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发表时间：
2000-08-15
影响因子：
11.1
通讯作者：
Lichten, M
中科院分区：
文献类型：
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作者：
Goldman, ASH;Lichten, M
在酿酒酵母减数分裂中，重组经常发生在同源物上同一位置的序列之间（等位基因重组），并且可以发生在分散的同源序列之间（异位重组）。异位重组比等位基因重组发生的频率要低，特别是当同源序列位于异源染色体上时。为了解释这一点，有人建议同源配对（同源共定位和比对）要么促进等位基因重组，要么限制异位重组。通过在正常同源关系被破坏的两种情况下检查异位重组来测试后一个建议。在第一种情况下，同源对的一个成员被同源（相关但不相同）染色体取代，该染色体已充分分化以防止等位基因重组。在第二种情况下，ndj1 突变体被用来延迟同源配对和突触。这两种情况都会导致异源染色体上含有 arg4 的质粒插入片段之间异位重组频率的大幅增加。这些发现表明，在正常酵母减数分裂期间，进行性同源共定位、比对、突触和等位基因重组限制了异位定位序列彼此发现和重组的能力。在没有此类限制的情况下，减数分裂同源性搜索可能涵盖整个基因组。
In Saccharomyces cerevisiae meiosis, recombination occurs frequently between sequences at the same location on homologs (allelic recombination) and can take place between dispersed homologous sequences (ectopic recombination). Ectopic recombination occurs less often than does allelic, especially when homologous sequences are on heterologous chromosomes. To account for this, it has been suggested that homolog pairing (homolog colocalization and alignment) either promotes allelic recombination or restricts ectopic recombination. The latter suggestion was tested by examining ectopic recombination in two cases where normal interhomolog relationships are disrupted. In the first case, one member of a homolog pair was replaced by a homoeologous (related but not identical) chromosome that has diverged sufficiently to prevent allelic recombination. In the second case, ndj1 mutants were used to delay homolog pairing and synapsis. Both circumstances resulted in a substantial increase in the frequency of ectopic recombination between arg4-containing plasmid inserts located on heterologous chromosomes. These findings suggest that, during normal yeast meiosis, progressive homolog colocalization, alignment, synapsis, and allelic recombination restrict the ability of ectopically located sequences to find each other and recombine. In the absence of such restrictions, the meiotic homology search may encompass the entire genome.