Barr G C, Ni Bhriain N, Dorman C J
Department of Biochemistry, University of Dundee, Scotland.
J Bacteriol. 1992 Feb;174(3):998-1006. doi: 10.1128/jb.174.3.998-1006.1992.
The Escherichia coli K-12 gene coding for the nucleoid-associated protein HNS was cloned together with 5.6 kb of downstream DNA in the vector pACYC184. The cloned DNA complemented a mutation in the osmZ locus of E. coli, which codes for HNS. However, the multicopy plasmid harboring the cloned sequence was found to be mutagenic and to produce at high frequency mutations that mapped to the E. coli cya gene, which codes for adenylate cyclase. Acquisition of the cya mutations was independent of RecA. These mutations were phenotypically suppressed by providing the cells with exogenous cyclic AMP and were complemented in trans by a plasmid carrying an active copy of the cya gene. A deletion analysis of the cloned sequences showed that DNA downstream of the gene coding for HNS was also required for the mutagenic effect of cya and had a role in regulating the expression of the osmZ-dependent proU locus. These sequences appear to contain at least two genetically active regions.
编码类核相关蛋白HNS的大肠杆菌K-12基因与5.6 kb的下游DNA一起克隆到载体pACYC184中。克隆的DNA弥补了大肠杆菌osmZ位点的突变，该位点编码HNS。然而，发现携带克隆序列的多拷贝质粒具有致突变性，并高频产生定位到编码腺苷酸环化酶的大肠杆菌cya基因的突变。cya突变的获得不依赖于RecA。通过为细胞提供外源性环磷酸腺苷，这些突变在表型上得到抑制，并被携带cya基因活性拷贝的质粒反式互补。对克隆序列的缺失分析表明，编码HNS的基因下游的DNA对于cya的致突变作用也是必需的，并且在调节osmZ依赖性proU位点的表达中起作用。这些序列似乎包含至少两个遗传活性区域。
