Gigliani F, Ciotta C, Del Grosso M F, Battaglia P A
Dipartimento di Biopatologia Umana, Università La Sapienza, Policlinico Umberto, Roma, Italy.
Mol Gen Genet. 1993 Apr;238(3):333-8. doi: 10.1007/BF00291991.
Evidence is presented that the pR bat gene is essential for plasmid replication and for spontaneous induction of the SOS response in Escherichia coli. Mutations preventing single-stranded DNA production, needed for pR plasmid replication, also prevent the induction of the SOS system. The following experimental design was used. Firstly, we identified the minima rep region, defined as the minimal DNA sequence necessary for pR plasmid replication and, secondly, analyzed the nucleotide sequence of this region. This identified structures and functions (ori-plus, ori-minus and Rep protein) homologous to those found in phages and plasmids replicating by the rolling-circle mechanism. Finally, mutations were introduced either in the replication protein catalytic site or in the nick site consensus sequence, which caused the pR plasmid to lose its ability to induce the SOS system. We conclude that, in this system, the in vivo SOS-inducing signal appears to be the single-stranded DNA produced during pR replication.
有证据表明，pR蝙蝠基因对于大肠杆菌中质粒复制和SOS应答的自发诱导至关重要。阻止pR质粒复制所需的单链DNA产生的突变，也会阻止SOS系统的诱导。采用了以下实验设计。首先，我们确定了最小rep区域，定义为pR质粒复制所需的最小DNA序列，其次，分析了该区域的核苷酸序列。这确定了与通过滚环机制复制的噬菌体和质粒中发现的结构和功能（正向ori、反向ori和Rep蛋白）同源。最后，在复制蛋白催化位点或切口位点共有序列中引入突变，这导致pR质粒失去诱导SOS系统的能力。我们得出结论，在这个系统中，体内SOS诱导信号似乎是pR复制过程中产生的单链DNA。
