Régnier P, Portier C
J Mol Biol. 1986 Jan 5;187(1):23-32. doi: 10.1016/0022-2836(86)90403-1.
The rpsO gene of Escherichia coli, which encodes ribosomal protein S15 is located at 69 minutes on the chromosome. It is adjacent to the pnp gene, which encodes polynucleotide phosphorylase. The two genes are separated by 249 nucleotides and are transcribed in the same direction. We report here in vivo S1 nuclease mapping and in vitro transcription experiments that demonstrate that rpsO and pnp are cotranscribed from a promoter P1, located 108 nucleotides upstream from rpsO, and that another promoter P2, located between the two genes 158 nucleotides upstream from pnp, also directs the transcription of pnp. Transcription from P1 can either terminate at the terminator t1 identified in vivo and in vitro, 18 nucleotides downstream from rpsO, or transcribe through t1 and into pnp. Comparison of the transcripts synthesized in wild-type and RNase III-deficient strains of E. coli shows that all the P1 readthrough transcripts and P2 transcripts are cleaved by RNase III. Two specific cuts are made by RNase III in a double-stranded structure about 100 nucleotides upstream rpsO. We also found that some transcripts of this operon start 47 nucleotides downstream from rpsO, in the region of t1. No promoter has been identified in this region. This mRNA is attributed to an endonucleolytic cleavage of the polycistronic transcripts and the location of the cut is named M. The order of the transcription signals and of the maturation sites in relation to rpsO and pnp can be summarized as follows: P1, rpsO, t1, M, P2, RNase III-processing sites, pnp. The possible roles of mRNA processing events in the expression of rpsO-pnp operon are discussed.
大肠杆菌的rpsO基因编码核糖体蛋白S15，位于染色体的69分钟处。它与编码多核苷酸磷酸化酶的pnp基因相邻。这两个基因被249个核苷酸隔开，并以相同方向转录。我们在此报告体内S1核酸酶作图和体外转录实验，这些实验表明rpsO和pnp从位于rpsO上游108个核苷酸处的启动子P1共同转录，并且另一个位于两个基因之间、pnp上游158个核苷酸处的启动子P2也指导pnp的转录。从P1转录可以在体内和体外确定的终止子t1处终止，t1位于rpsO下游18个核苷酸处，或者转录通过t1进入pnp。对野生型和RNase III缺陷型大肠杆菌菌株中合成的转录本进行比较表明，所有P1通读转录本和P2转录本都被RNase III切割。RNase III在rpsO上游约100个核苷酸的双链结构中进行两次特异性切割。我们还发现该操纵子的一些转录本在rpsO下游47个核苷酸处的t1区域开始。该区域未鉴定出启动子。这种mRNA归因于多顺反子转录本的内切核酸酶切割，切割位置命名为M。转录信号和成熟位点相对于rpsO和pnp的顺序可总结如下：P1、rpsO、t1、M、P2、RNase III加工位点、pnp。讨论了mRNA加工事件在rpsO - pnp操纵子表达中的可能作用。
