Machida C, Machida Y, Ohtsubo E
J Mol Biol. 1984 Aug 5;177(2):247-67. doi: 10.1016/0022-2836(84)90455-8.
Escherichia coli RNA polymerase was found to bind specifically to restriction fragments containing either end of IS1. DNase I footprint analyses indicate that RNA polymerase protects approximately 70 base-pairs at each end of IS1, including the left or right terminal inverted repeat sequences in IS1 (termed insL or insR, respectively) as well as some non-IS1 sequence directly adjacent to each end of IS1. Analysis of transcripts from the left terminal region of IS1 shows that the insL sequence contains a promoter (named insPL), and that RNA synthesis initiates apparently at one in a stretch of five adenylate residues within insL and continues toward the interior region of IS1. Interestingly, most of the resulting transcripts contain polyuridylate residues (more than 5 U residues) at their 5'-ends. Analysis of transcripts from the right terminal region of IS1 indicates that the insR sequence also contains a promoter (named insPR). RNA synthesis initiates specifically at an adenylate residue within insR and continues toward the interior region of IS1, i.e. in the opposite direction to RNA synthesis initiating at insPL, which is present at the other end of IS1. We propose that insPL is used to make the messenger RNA for the IS1-encoded genes insA and insB, while insPR might be used to synthesize an anti-mRNA and thereby negatively regulate insPL.
人们发现大肠杆菌RNA聚合酶能特异性结合含有IS1两端的限制性片段。DNA酶I足迹分析表明，RNA聚合酶在IS1的两端各保护约70个碱基对，包括IS1中的左或右末端反向重复序列（分别称为insL或insR）以及直接毗邻IS1两端的一些非IS1序列。对IS1左末端区域转录本的分析表明，insL序列含有一个启动子（命名为insPL），并且RNA合成显然在insL内五个腺苷酸残基的一段序列中的一个位点起始，并朝着IS1的内部区域延伸。有趣的是，大多数产生的转录本在其5'-末端含有聚尿苷酸残基（超过5个U残基）。对IS1右末端区域转录本的分析表明，insR序列也含有一个启动子（命名为insPR）。RNA合成在insR内的一个腺苷酸残基处特异性起始，并朝着IS1的内部区域延伸，即与在IS1另一端的insPL处起始的RNA合成方向相反。我们提出，insPL用于合成IS1编码基因insA和insB的信使RNA，而insPR可能用于合成一种反义mRNA，从而对insPL进行负调控。
