THE AT RICHNESS AND GID TRANSCRIPTION DETERMINE THE LEFT BORDER OF THE REPLICATION ORIGIN OF THE ESCHERICHIA-COLI CHROMOSOME
THE AT RICHNESS AND GID TRANSCRIPTION DETERMINE THE LEFT BORDER OF THE REPLICATION ORIGIN OF THE ESCHERICHIA-COLI CHROMOSOME
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DOI：
10.1002/j.1460-2075.1990.tb07628.x
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发表时间：
1990-12-01
期刊：
影响因子：
11.4
通讯作者：
IMAI, M
中科院分区：
文献类型：
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作者：
ASAI, T;TAKANAMI, M;IMAI, M
我们已经确定了新的，顺式作用元件，增强在体内的复制活性的质粒携带最小的oriC的大肠杆菌。这些是（i）富含AT的序列（“AT簇”），其存在于13聚体重复序列的紧左侧，和（ii）gid转录单位。“AT簇”在功能上被不相关的AT富集序列取代。这也是左侧和中间13聚体的情况;它们被来自mini-F质粒的富含AT的片段取代。左边的13聚体被富含AT的序列所取代，但没有显示出13聚体区域的重要特征“螺旋稳定性降低”。与这些结果相反，严格要求正确的13聚体序列。至于gid启动子转录的影响，最小oriC只有在转录方向远离oriC左侧时才被激活。mioC转录向oriC方向进行对激活没有影响。在DnaA盒中的突变被gid转录部分抑制，从左侧留下oriC。根据这些结果，我们提出AT丰富度是识别oriC左边界的决定因素。据推测，gid转录在富含AT的区域引入负超螺旋性，并促进DnaA依赖性双链体打开。
We have identified novel, cis-acting elements which enhance in vivo the replication activity of plasmids carrying the minimal oriC of Escherichia coli. These are (i) the AT rich sequence (''AT-cluster'') which exists immediately left of the 13mer repeats and (ii) the gid transcriptional unit. The ''AT-cluster'' was functionally replaced by an unrelated AT rich sequence. This was also the case for the left and middle 13mers; they were substituted by the AT rich fragment from mini-F plasmid. The left 13mer was replaced by the AT rich sequence whcih did not show the ''reduced helical stability'' known as the important character of the 13mer region. In contrast to these results, the right 13mer sequence was strictly required. As to the effect of the transcription from the gid promoter, the minimal oriC was activated only when the transcription was directed away from the left side of it. mioC transcription proceeding toward the oriC had no effect on the activation. Mutations in the DnaA boxes were partially suppressed by gid transcription leaving oriC from the left side. From these results, we propose that the AT richness is a determinant to identify the left border of oriC. It is presumed that gid transcription introduces negative superhelicity at the AT rich region and facilitates DnaA dependent duplex opening.