REPRESSION OF ESCHERICHIA-COLI PURB IS BY A TRANSCRIPTIONAL ROADBLOCK MECHANISM
REPRESSION OF ESCHERICHIA-COLI PURB IS BY A TRANSCRIPTIONAL ROADBLOCK MECHANISM
复制标题
DOI：
10.1128/jb.174.22.7121-7127.1992
复制
发表时间：
1992-11-01
影响因子：
3.2
通讯作者：
ZALKIN, H
中科院分区：
文献类型：
--
作者：
HE, B;ZALKIN, H
大肠杆菌purB受阻遏物-操纵基因相互作用的调控。purB操纵子位于转录起始位点下游242 bp处，并与蛋白质编码序列（B）中的密码子62至67重叠。他，J.M. Smith和H. Zalkin，J. Bacteriol. 174：130-136，1992）。通过启动子替代实验和RNA分析相结合，研究了阻遏物-操纵基因相互作用抑制转录的机制。通过使用缺失5'侧翼DNA至位置-986的trp启动子替换，purB表达增加7倍，但维持正常的2 - 3倍调节。这表明阻遏物-操纵基因控制不依赖于purB启动子和其他5'侧翼序列。转录调控同样独立于偶联翻译。一个约260个核苷酸的截短的体内purB mRNA被确定，这是依赖于repressoroperator相互作用。因此，嘌呤阻遏物与purB操纵子的结合通过路障机制抑制转录延伸。路障是不受影响的启动子强度增加7倍，或由一个操纵基因突变，导致阻遏物-操纵基因亲和力增加2.5倍。
Escherichia coli purB is regulated by a repressor-operator interaction. The purB operator is 242 bp downstream from the transcription start site and overlaps codons 62 to 67 in the protein-coding sequence (B. He, J. M. Smith, and H. Zalkin, J. Bacteriol. 174:130-136, 1992). The mechanism by which the repressor-operator interaction functions to repress transcription was investigated by a combination of promoter replacement experiments and RNA analyses. By using a trp promoter replacement that deleted 5' flanking DNA to position -986, purB expression was increased sevenfold, yet normal two- to threefold regulation was maintained. This indicates that repressor-operator control is independent of the purB promoter and other 5' flanking sequences. Transcriptional regulation was likewise independent of coupled translation. An approximately 260-nucleotide truncated in vivo purB mRNA was identified which was dependent upon repressoroperator interaction. Thus, binding of purine repressor to the purB operator inhibits transcription elongation by a roadblock mechanism. The roadblock was not influenced by a sevenfold increase in promoter strength or by an operator mutation resulting in a 2.5-fold increase in repressor-operator affinity.