Zassenhaus H P, Denniger G
Department of Molecular Microbiology and Immunology, St. Louis University Medical Center, MO 63104.
Curr Genet. 1994 Feb;25(2):142-9. doi: 10.1007/BF00309540.
Mitochondrial DNA recombination was reduced in an yeast mutant lacking the NUC1 endo/exonuclease. Between linked markers in either the omega or cob region the frequency of recombination decreased nearly 50% compared to wild-type. Gene conversion frequencies in the var1 gene and in the omega region were also lower in the mutant strain. In particular, the gradient of gene conversion at omega was most affected by the absence of the NUC1 nuclease. In crosses between nuclease-deficient and wild-type strains, gene conversion frequencies at omega were reduced only when the omega+ allele was contributed to the zygote by the nuclease-deficient parent. We propose that the 5' exonuclease activity of the NUC1 nuclease functions during recombination to enlarge heteroduplex tracts following a double-strand break in DNA. In crosses between nuclease-deficient and wild-type strains, the anisotropy in gene conversion frequencies at omega is hypothesized to be due to the slow mixing of parental mitochondrial membranes as they fuse in the zygote.
在缺乏NUC1核酸内切酶/外切酶的酵母突变体中，线粒体DNA重组减少。与野生型相比，在ω或cob区域的连锁标记之间，重组频率降低了近50%。突变菌株中var1基因和ω区域的基因转换频率也较低。特别是，ω处的基因转换梯度受NUC1核酸酶缺失的影响最大。在核酸酶缺陷型和野生型菌株之间的杂交中，只有当ω+等位基因由核酸酶缺陷型亲本贡献给合子时，ω处的基因转换频率才会降低。我们提出，NUC1核酸酶的5'外切酶活性在重组过程中发挥作用，以在DNA双链断裂后扩大异源双链区域。在核酸酶缺陷型和野生型菌株之间的杂交中，ω处基因转换频率的不对称性被认为是由于亲本线粒体膜在合子中融合时混合缓慢所致。
