Thode S, Schäfer A, Pfeiffer P, Vielmetter W
Institute of Genetics, University of Cologne, Federal Republic of Germany.
Cell. 1990 Mar 23;60(6):921-8. doi: 10.1016/0092-8674(90)90340-k.
Repair mechanisms related to illegitimate recombination can join nonhomologous DNA ends that terminate as protruding single strands (PSS). Here we analyze in Xenopus egg extracts joining reactions between 3' PSS termini and various partner termini. In junctions, 3' PSS termini are preserved by fill-in DNA synthesis, although their 5' recessed ends cannot serve as a primer. Alternative priming from a partner terminus ligated to the 3' PSS end appears unlikely, because no single strand-specific DNA ligases are detectable. We show that fill-in of 3' PSS termini precedes ligation and can even be primed in the absence of any ligation. Therefore, priming requires precise alignment of terminus pairs by a novel mechanism. We postulate that this is achieved by unique DNA binding proteins that align ends in various types of joining reactions.
与异常重组相关的修复机制能够连接以突出单链（PSS）形式终止的非同源DNA末端。在此，我们分析了非洲爪蟾卵提取物中3' PSS末端与各种配对末端之间的连接反应。在连接点处，3' PSS末端通过填补DNA合成得以保留，尽管其5'凹陷末端不能作为引物。从连接到3' PSS末端的配对末端进行替代引物延伸似乎不太可能，因为未检测到单链特异性DNA连接酶。我们发现3' PSS末端的填补先于连接，甚至在没有任何连接的情况下也能引发。因此，引物延伸需要通过一种新机制使末端精确对齐。我们推测这是通过独特的DNA结合蛋白实现的，这些蛋白在各种类型的连接反应中使末端对齐。
