T4 endonuclease VII cleaves the crossover strands of Holliday junction analogs.
T4 endonuclease VII cleaves the crossover strands of Holliday junction analogs.
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T4 核酸内切酶 VII 可切割霍利迪连接体类似物的交叉链。
DOI：
10.1073/pnas.85.24.9441
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发表时间：
1988
影响因子：
11.1
通讯作者：
Seeman,NC
中科院分区：
文献类型：
--
作者：
Mueller,JE;Kemper,B;Cunningham,RP;Kallenbach,NR;Seeman,NC
我们已经形成了四臂分支的DNA连接，其中包含不超过一个碱基对的分支迁移自由。最近，我们已经表明，这些霍利迪连接类似物在溶液中具有双重对称的保护模式时，探测与羟基自由基：一个交界处的两个相反的链显示出广泛的保护附近的分支点，而另一对相反的链几乎是敏感的双螺旋。在不同的连接中，羟基自由基保护模式被逆转。这些模式表明，交叉异构体的偏见存在于这些分子和受保护的链形成的螺旋之间的交叉。在这里，我们检查这些结构的切割模式时，他们被T4核酸内切酶VII解决。连接由单个三叶草形分子形成，其包含5 '，3'或内部标记。该酶显示出优先解决这些修改后的路口附近的网站保护羟基自由基。该结果表明，只有霍利迪连接中的交叉链被切割，因此当侧翼标记交换时，必须发生奇数次交叉异构化。
We have formed four-arm branched DNA junctions that contain no more than a single base pair of branch migratory freedom. Recently, we have shown that these Holliday junction analogs have twofold symmetric protection patterns in solution when probed with hydroxyl radicals: two opposite strands of one junction show extensive protection near the branch point, while the other pair of opposite strands is virtually as susceptible as a double helix. In a different junction, the hydroxyl radical protection pattern is reversed. These patterns suggest that a crossover-isomer bias exists in these molecules and that the protected strands form the crossover between helices. Here, we examine the cleavage pattern of these structures when they are resolved by T4 endonuclease VII. Junctions are formed from a single shamrock-shaped molecule, which contains 5', 3', or internal labels. The enzyme shows a preference for resolving these modified junctions at sites near those protected from hydroxyl radicals. This result suggests that only crossover strands in a Holliday junction are cleaved, and thus an odd number of crossover isomerizations must occur when flanking markers are exchanged.