Shibata T, Nakagawa K, Morishima N
Laboratory of Cellular and Molecular Biology, Institute of Physical and Chemical Research (RIKEN), Saitama, Japan.
Adv Biophys. 1995;31:77-91. doi: 10.1016/0065-227x(95)99384-2.
The notion that homologous recombination is a regulated biological process is not a familiar one. In yeasts, homologous recombination and most site-specific ones are initiated by site-specific double-stranded breaks that are introduced within cis-acting elements for the recombination. On the other hand, yeasts have a group of site-specific endonucleases (multi-site-specific endonucleases) that have a number of cleavage sites on each DNA. One of them, Endo.SceI of S. cerevisiae, was shown to introduce double-stranded breaks at a number of well-defined sites on the mitochondrial DNA in vivo. An Endo.SceI-induced double-stranded break was demonstrated to induce homologous recombination in mitochondria. Like the case of homologous recombination of nuclear chromosomes, the double-stranded break induces gene conversion of both genetic markers flanking and in the proximity of the cleavage site, and the cleaved DNA acts as a recipient of genetic information from the uncleaved partner DNA. The 70 kDa-heat-shock protein (HSP70)-subunit of Endo.SceI and a general role of the HSP70 in the regulation of protein-folding suggest the regulation of nucleolytic activity of Endo.SceI.
同源重组是一个受调控的生物学过程，这一概念并不为人所熟知。在酵母中，同源重组和大多数位点特异性重组是由位点特异性双链断裂引发的，这些断裂是在用于重组的顺式作用元件内引入的。另一方面，酵母有一种位点特异性核酸内切酶（多位点特异性核酸内切酶），每种DNA上都有多个切割位点。其中之一，酿酒酵母的Endo.SceI，已被证明在体内在线粒体DNA的多个明确位点引入双链断裂。Endo.SceI诱导的双链断裂被证明可诱导线粒体中的同源重组。与核染色体的同源重组情况一样，双链断裂诱导切割位点两侧及附近的遗传标记发生基因转换，并且切割后的DNA充当来自未切割的伙伴DNA的遗传信息的接受者。Endo.SceI的70 kDa热休克蛋白（HSP70）亚基以及HSP70在蛋白质折叠调控中的一般作用表明Endo.SceI的核酸水解活性受到调控。
