Cousineau B, Smith D, Lawrence-Cavanagh S, Mueller J E, Yang J, Mills D, Manias D, Dunny G, Lambowitz A M, Belfort M
Wadsworth Center, New York State Department of Health, and School of Public Health, State University of New York at Albany, 12201-2002, USA.
Cell. 1998 Aug 21;94(4):451-62. doi: 10.1016/s0092-8674(00)81586-x.
The mobile group II intron of Lactococcus lactis, Ll.LtrB, provides the opportunity to analyze the homing pathway in genetically tractable bacterial systems. Here, we show that Ll.LtrB mobility occurs by an RNA-based retrohoming mechanism in both Escherichia coli and L. lactis. Surprisingly, retrohoming occurs efficiently in the absence of RecA function, with a relaxed requirement for flanking exon homology and without coconversion of exon markers. These results lead to a model for bacterial retrohoming in which the intron integrates into recipient DNA by complete reverse splicing and serves as the template for cDNA synthesis. The retrohoming reaction is completed in unprecedented fashion by a DNA repair event that is independent of homologous recombination between the alleles. Thus, Ll.LtrB has many features of retrotransposons, with practical and evolutionary implications.
乳酸乳球菌的移动性II类内含子Ll.LtrB，为在遗传上易于操作的细菌系统中分析归巢途径提供了机会。在此，我们表明Ll.LtrB的移动性在大肠杆菌和乳酸乳球菌中均通过基于RNA的反转归巢机制发生。令人惊讶的是，在没有RecA功能的情况下，反转归巢能高效发生，对外显子侧翼同源性的要求较为宽松，且外显子标记不会共转化。这些结果得出了一个细菌反转归巢模型，其中内含子通过完全反向剪接整合到受体DNA中，并作为cDNA合成的模板。反转归巢反应以前所未有的方式通过一个独立于等位基因间同源重组的DNA修复事件完成。因此，Ll.LtrB具有反转录转座子的许多特征，具有实际和进化意义。
