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首页> 外文期刊>Molecular and Cellular Biology >Effect of limited homology on gene conversion in a Saccharomyces cerevisiae plasmid recombination system.
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Effect of limited homology on gene conversion in a Saccharomyces cerevisiae plasmid recombination system.

机译：在啤酒酵母质粒重组系统中有限同源性对基因转化的影响。

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摘要

Plasmids containing heteroallelic copies of the Saccharomyces cerevisiae HIS3 gene undergo intramolecular gene conversion in mitotically dividing S. cerevisiae cells. We have used this plasmid system to determine the minimum amount of homology required for gene conversion, to examine how conversion tract lengths are affected by limited homology, and to analyze the role of flanking DNA sequences on the pattern of exchange. Plasmids with homologous sequences greater than 2 kilobases have mitotic exchange rates as high as 2 x 10(-3) events per cell per generation. As the homology is reduced, the exchange rate decreases dramatically. A plasmid with 26 base pairs (bp) of homology undergoes gene conversion at a rate of approximately 1 x 10(-10) events per cell per generation. These studies have also shown that an 8-bp insertion mutation 13 bp from a border between homologous and nonhomologous sequences undergoes conversion, but that a similar 8-bp insertion 5 bp from a border does not. Examination of independent conversion events which occurred in plasmids with heteroallelic copies of the HIS3 gene shows that markers within 280 bp of a border between homologous and nonhomologous sequences undergo conversion less frequently than the same markers within a more extensive homologous sequence. Thus, proximity to a border between homologous and nonhomologous sequences shortens the conversion tract length.
机译：含有酿酒酵母HIS3基因的杂等位基因拷贝的质粒在有丝分裂的酿酒酵母细胞中进行分子内基因转化。我们已经使用该质粒系统来确定基因转化所需的最小同源量，以检查转化道长度如何受到有限同源性的影响，并分析侧翼DNA序列在交换模式中的作用。同源序列大于2 KB的质粒每代每一细胞的有丝分裂交换率高达2 x 10（-3）个事件。随着同源性的降低，汇率急剧下降。具有26个碱基对（bp）同源性的质粒以每个细胞每代大约1 x 10（-10）个事件的速率进行基因转化。这些研究还表明，从同源序列和非同源序列之间的边界开始的13 bp处的8 bp插入突变发生了转化，但是从边界开始的5 bp处的类似8 bp插入突变没有发生。检查具有HIS3基因的异等位基因拷贝的质粒中发生的独立转化事件表明，与同源序列和非同源序列之间的边界相比，同源和非同源序列之间边界的280 bp内的标记进行转化的频率较低。因此，接近同源序列和非同源序列之间的边界会缩短转化管道的长度。

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