NUCLEOTIDE-SEQUENCE PREFERENCE AT RAT-LIVER AND WHEAT-GERM TYPE-1 DNA TOPOISOMERASE BREAKAGE SITES IN DUPLEX SV40 DNA
NUCLEOTIDE-SEQUENCE PREFERENCE AT RAT-LIVER AND WHEAT-GERM TYPE-1 DNA TOPOISOMERASE BREAKAGE SITES IN DUPLEX SV40 DNA
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DOI：
10.1093/nar/12.7.3097
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发表时间：
1984-01-01
影响因子：
14.9
通讯作者：
CHAMPOUX, JJ
中科院分区：
文献类型：
--
作者：
BEEN, MD;BURGESS, RR;CHAMPOUX, JJ
研究了大鼠肝脏和小麦胚中1型DNA拓扑异构酶(Topo-1)的位点特异性。测定了245个小麦胚芽Topo 1位点和223个大鼠肝脏Topo 1位点的双链SV40 DNA断裂点的1781个核苷酸序列。这两种不同来源的酶显示出相似但不相同的DNA链断裂模式。这些站点经常出现，但不是以相等的概率被破坏。主要的断裂部位平均每一到两圈螺旋出现一次，因此，如果断裂部位准确地代表了Topo 1的活性部位，那么DNA序列本身似乎对酶对DNA的访问几乎没有限制。两种酶最强位点附近的序列显示，4个核苷酸的碱基组成在5‘端与断裂位置(−4至−1位置)之间存在偏差，但没有3’端与断裂部位的偏向。确定了两种酶的共同序列。与共同序列的差异似乎对两种酶的影响不同，可能解释了观察到的断裂特异性的差异。
The site specificities of the type 1 DNA topoisomerases (topo 1) from rat liver and wheat germ were investigated. The nucleotide sequence at break sites on duplex SV40 DNA were determined for 245 wheat germ topo 1 sites and 223 rat liver topo 1 sites over a region of 1781 nucleotides. The enzymes from the two different sources show similar, but not identical patterns of DNA strand breakage. The sites occur frequently, but are not broken with equal probabilities. Major sites of breakage occur on the average every one to two turns of the helix, thus if sites of breakage accurately represent topo 1 sites of activity, the DNA sequence alone would appear to place few limits on the access of the enzyme to DNA. Sequences around the strongest sites for both enzymes show a bias in base composition for the four nucleotides immediately 5′ to the break site (−4 to −1 positions), but no bias is observed 3′ to the site of breakage. Consensus sequences for both enzymes were determined. Variations from the consensus sequence appear to affect the two enzymes differently and may account for the differences observed in the specificity of breakage.