TRANSCRIPTIONAL ORGANIZATION OF THE ESCHERICHIA-COLI DNAX GENE
TRANSCRIPTIONAL ORGANIZATION OF THE ESCHERICHIA-COLI DNAX GENE
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DOI：
10.1016/0022-2836(91)90107-h
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发表时间：
1991-08-05
影响因子：
5.6
通讯作者：
MCHENRY, CS
中科院分区：
文献类型：
--
作者：
FLOWER, AM;MCHENRY, CS
我们已经确定了大肠杆菌dnaX基因的转录组织，该基因是DNA聚合酶III全酶γ和τ亚基的结构基因。通过S1核酸酶保护和引物延伸图谱分析，确定了dnaX基因的一个启动子，该启动子位于第一个密码子上游37个核苷酸处，dnaX基因位于一个操纵子中，该操纵子包含两个新近测序的基因：orf 12和recR，orf 12编码一个未鉴定的产物，recR是一个参与recF重组途径的蛋白的结构基因。在平衡生长的条件下，来自上游ap启动子的非常少量的转录（<5%）有助于τ和γ的表达，太低以至于不能被认为是在具有dnaX的操纵子上，orf 12和recRare从独立的启动子以及从dnaX启动子转录，提供了orf 12和recR独立于dnaX调节的机制。转录的dnaX-orf 12-recRoperon终止上游的先前表征的热休克基因htpG。将dnaX和orf 12-recR启动子克隆到启动子检测载体中，有效地指导下游报告基因lacZ的表达。这些结果扩展了我们对E.大肠染色体其转录组构被定义为：apt，dnaX-orf 12-recR，htpG。所有这些基因都是顺时针方向转录的，只有dnaX，orf 12和recRare包含在dnaX操纵子中。
We have determined the transcriptional organization of theEscherichia coli dnaXgene, the structural gene for both the γ and τ subunits of DNA polymerase III holoenzyme. By S1nuclease protection and primer extension mapping of transcripts encoding thednaXproducts, one primary promoter ofdnaXhas been identified that initiates transcription 37 nucleotides upstream from the first codon.dnaXresides in an operon with two recently sequenced genes,orf12, encoding an unidentified product, andrecR, the structural gene for a protein involved in therecFpathway of recombination. Under conditions of balanced growth, a very small amount of transcription from the upstreamaptpromoter (<5%) contributes to the expression of τ and γ, too low foraptto be considered to be on an operon withdnaX.orf12andrecRare transcribed from an independent promoter as well as from thednaXpromoter, providing a mechanism fororf12andrecRto be regulated independent ofdnaX. Transcription of thednaX-orf12-recRoperon is terminated upstream from the previously characterized heat shock genehtpG. ThednaXandorf12-recRpromoters, cloned into a promoter detection vector, efficiently direct the expression of the downstream reporter gene,lacZ. These results extend our knowledge of the genetic and transcriptional organization of this region of theE. colichromosome. The transcriptional organization has been defined as follows:apt,dnaX-orf12-recR,htpG. All of these genes are transcribed in the clockwise direction and onlydnaX,orf12andrecRare contained in thednaXoperon.