TERMINAL STAGES OF SV40 DNA-REPLICATION PROCEED VIA MULTIPLY INTERTWINED CATENATED DIMERS
TERMINAL STAGES OF SV40 DNA-REPLICATION PROCEED VIA MULTIPLY INTERTWINED CATENATED DIMERS
复制标题
DOI：
10.1016/0092-8674(80)90118-x
复制
发表时间：
1980-01-01
期刊：
影响因子：
64.5
通讯作者：
VARSHAVSKY, A
中科院分区：
文献类型：
--
作者：
SUNDIN, O;VARSHAVSKY, A
发现了一类新的SV 40复制中间体，它由至少20个离散的DNA种类组成。该类的所有成员都是连锁二聚体，即通过1个或多个缠绕事件拓扑连接的SV 40双链DNA的2个环状分子。这些分子中的大多数通过几个缠绕事件连接，并且观察到的连接状态的范围从L = 1到L = 10。根据其2个环状组分的开放或共价闭合性质，将具有给定键合状态的链状二聚体分配到3个不同家族（A、B或C）中的1个：在A型链状二聚体中，两个环都有切口或缺口;在B型中，其中一个环是超螺旋的;在C型中，两个环都是超螺旋的。所有这3个家族的成员都存在于用3 H-胸苷脉冲标记的SV 40染色质中，它们共同构成了总复制形式SV 40 DNA的10-20%，表现为叠加在生长的凯恩斯结构的连续涂片上的一系列离散的电泳分辨条带。连锁状态的分布在不同的家庭之间，A是最交织和C交织最少。在用冷胸苷追踪时，标记从所有这些连锁DNA种类中迅速丢失。序列A →B →C.成熟的单体超螺旋SV 40 DNA显然代表了SV 40复制的最后阶段，并且在体内存在一种特殊的酶活性来解链SV 40子染色体。
A new class of SV40 replicative intermediates which consists of at least 20 discrete DNA species were identified. All members of this class are catenated dimers, 2 circular molecules of SV40 duplex DNA linked topologically by 1 or more intertwining events. Most of these molecules are linked by several intertwining events, and the range of linkage states observed runs from L = 1 to L = 10. A catenated dimer with a given linkage state is assigned to 1 of 3 distinct families (A, B or C) depending on the open or covalently closed nature of its 2 circular components: in form A catenated dimers, both circles are nicked or gapped; in form B, 1 of the circles is supercoiled; and in form C, both circles are supercoiled. Members of all 3 of these families are found in SV40 chromatin pulse-labeled with 3H-thymidine, and together they comprise 10-20% of the total replicative form SV40 DNA, appearing as a discrete series of electrophoretically resolved bands superimposed upon a continuous smear of growing cairns structures. The distribution of linkage states varies between the families, A being the most intertwined and C the least intertwined. Upon a chase with cold thymidine, label is lost rapidly from all these catenated DNA species. The sequence A .fwdarw. B .fwdarw. C .fwdarw. mature monomeric supercoiled SV40 DNA apparently represents the final stages of SV40 replication, and a special enzyme activity exists in vivo to uncatenate the SV40 daughter chromosomes.