Morishima N, Nakagawa K, Shibata T
Laboratory of Microbiology, Institute of Physical and Chemical Research (RIKEN), Saitama, Japan.
Curr Genet. 1993 May-Jun;23(5-6):537-41. doi: 10.1007/BF00312648.
Endo.SceI most likely initiates homologous recombination of yeast mitochondrial genome through sequence-specific double-strand scission of DNA. According to the double-strand break-repair model for the mechanism of homologous recombination, DNA ends created by sequence-specific endonucleases have to be processed by exonucleases. The major mitochondrial exonuclease (encoded by NUC1) has been shown to greatly affect the length of conversion tracts at the 21S rRNA locus when site-specific gene conversion is induced by omega endonuclease. In order to examine the role of the NUC1 nuclease in the Endo.SceI-induced recombination, recombination frequencies were measured after crossing of parental strains either in the presence or absence of NUC1 nuclease activity. The frequency of gene conversion in the oli2 locus induced by Endo.SceI was not reduced by disruption of the NUC1 gene. This result strongly implicates the presence of multiple exonucleases for the processing of the DNA ends created by sequence-specific endonucleases.
Endo.SceI很可能通过DNA的序列特异性双链断裂引发酵母线粒体基因组的同源重组。根据同源重组机制的双链断裂修复模型，由序列特异性核酸内切酶产生的DNA末端必须由核酸外切酶进行处理。主要的线粒体核酸外切酶（由NUC1编码）已被证明，当由ω核酸内切酶诱导位点特异性基因转换时，它会极大地影响21S rRNA基因座处转换片段的长度。为了研究NUC1核酸酶在Endo.SceI诱导的重组中的作用，在有或没有NUC1核酸酶活性的情况下，对亲本菌株进行杂交后测量重组频率。Endo.SceI诱导的oli2基因座中的基因转换频率不会因NUC1基因的破坏而降低。这一结果有力地表明，存在多种核酸外切酶来处理由序列特异性核酸内切酶产生的DNA末端。
