STABILIZATION OF Z DNA INVIVO BY LOCALIZED SUPERCOILING
STABILIZATION OF Z DNA INVIVO BY LOCALIZED SUPERCOILING
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DOI：
10.1126/science.2678475
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发表时间：
1989-10-20
期刊：
影响因子：
56.9
通讯作者：
WELLS, RD
中科院分区：
文献类型：
--
作者：
RAHMOUNI, AR;WELLS, RD
转录等生物过程可在环状DNA上产生超卷曲结构域。通过从pBR322的四环素耐药基因（tet）的上游或下游克隆不同长度的（CG）束在体内采用Z结构的能力来研究这些结构域在大肠杆菌中的存在性。当从tet基因上游（Eco RI位点）克隆时，短至12个碱基对的片段采用Z型，而当该序列在下游（Sty I位点）克隆时，没有检测到Z型DNA，即使有74个碱基对（CG）区段，与较短的区段相比，B-Z过渡需要更少的超卷曲。因此，pBR322中不同位点的局部超线圈密度。这些数据证明了Z结构在体内的存在。当从tet基因上游（Eco RI位点）克隆时，短至12个碱基对的片段采用Z形式，而当该序列在下游（sti I位点）克隆时，即使具有74.sbd，也没有检测到Z DNA。碱基对（CG）束需要更少的超卷绕比短束为B-Z转变。因此，pBR322在不同位点的局部超线圈密度可高达-0.038，低至-0.021。这些数据证明了常见的自然序列中存在Z结构，并支持了体内负超旋域的概念。
Biological processes such as transcription may generate domains of supercoiling on a circular DNA. The existence of these domains in Escherichia coli was investigated by the ability of different lengths of (CG) tracts, cloned upstream or downstream from the tetracycline resistance gene (tet) of pBR322, to adopt the Z structure in vivo. Segments as short as 12 base pairs adopt the Z form when cloned upstream from the tet gene (Eco RI site), whereas no Z DNA was detected when this sequence was cloned downstream (Sty I site), even with a 74-base pair (CG) tract that requires less supercoiling than shorter tracts for the B-Z transition. Hence the localized supercoil density in pBR322 at different loci. These data demonstrate the existence of the Z structure in vivo. Segments as short as 12 base pairs adopt the Z form when cloned upstream from the tet gene (Eco RI site), whereas no Z DNA was detected when this sequence was cloned downstream (Sty I site), even with a 74.sbd.base pair (CG) tract that requires less supercoiling than shorter tracts for the B-Z transition. Hence the localized supercoil density in pBR322 can be as high as -0.038 and as low as -0.021 at different loci. These data demonstrate the existence of the Z structure for commonly found natural sequences and support the notion of domains of negative supercoiling in vivo.