Structure and function of the phage lambda att site: size, int-binding sites, and location of the crossover point.
Structure and function of the phage lambda att site: size, int-binding sites, and location of the crossover point.
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噬菌体 lambda att 位点的结构和功能：大小、int 结合位点和交叉点的位置。
DOI：
10.1101/sqb.1981.045.01.057
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发表时间：
1981
期刊：
影响因子：
--
通讯作者：
Landy,A
中科院分区：
文献类型：
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作者：
Mizuuchi,K;Weisberg,R;Enquist,L;Mizuuchi,M;Buraczynska,M;Foeller,C;Hsu,PL;Ross,W;Landy,A
大肠杆菌染色体（分别为 attP 和 attB）上特定 DNA 序列之间的相互重组在整合病毒基因组的接合处产生左（attL）和右（attR）原噬菌体附着（att）位点（有关评论，请参见 Gottesman 和 Weisberg 1971；Nash 1977）。所有这四个 att 位点在基因上都是相互区别的。然而，交叉发生在所有这些区域共有的 15 bp“核心区域”内（或其边界）（Landy 和 Ross 1977）。交叉不涉及亲本序列的任何降解和重新合成，也不涉及作为该机制的强制部分的新一轮DNA复制。这一说法最严格的证据来自最近对该反应的体外研究，并得到了此处报告的一些实验的进一步支持（另见 Nash 等人，本卷）。该反应不需要任何高能辅助因子，甚至底物环状 DNA 的超螺旋性也不会发生重大改变 (Mizuuchi et al. 1980)。整合重组和切除 (attL• attR) 重组都需要噬菌体特异性蛋白 Int 以及几个宿主大肠杆菌基因的产物 (Miller et al. 1979)。仅在切除重组中需要噬菌体蛋白 Xis。 Int 已被纯化至接近均质（Kikuchi 和 Nash 1978），已被证明具有 I 型 DNA 拓扑异构酶的功能（Kikuchi 和 Nash 1979；Nash 等人，本卷）。由于 Int 具有切割和重新密封磷酸二酯键的特性，因此它似乎很可能直接负责执行交叉事件，例如，通过涉及两组特定切口/闭合反应的拟议机制（Kikuchi 和 Nash 1979；Nash 等人，本卷）。
Reciprocal recombination between specific DNA sequences on the~ and E. coli chromosomes (attP and attB, respectively) gives rise to left (attL) and right (attR) prophage attachment (att) sites at the junctures of an integrated viral genome (for reviews, see Gottesman and Weisberg 1971; Nash 1977). All four of these att sites are genetically distinguishable from one another; however, the crossover occurs within (or at the boundaries of) a 15-bp" core region" that is common to all of them (Landy and Ross 1977). The crossover does not involve any degradation and resynthesis of the parental sequence nor a new round of DNA replication as a mandatory part of the mechanism. The most rigorous proof for this statement comes from recent in vitro studies of the reaction and is further supported by some of the experiments reported here (see also Nash et al., this volume). The reaction does not require any high-energy cofactor, and even the superhelicity of the substrate circular DNA does not undergo major alteration (Mizuuchi et al. 1980).Both integrative as well as excisive (attL• attR) recombination require the phage-specific protein Int, as well as the products of several host E. coli genes (Miller et al. 1979). The phage protein Xis is only required in excisive recombination. Int, which has been purified to near homogeneity (Kikuchi and Nash 1978), has been shown to function as a type-I DNA topoisomerase (Kikuchi and Nash 1979; Nash et al., this volume). Since Int has this property of cutting and resealing phosphodiester bonds, it seems very likely to be directly responsible for executing the crossover event, for example, by a proposed mechanism involving two sets of specific nicking/closing reactions (Kikuchi and Nash 1979; Nash et al., this volume).