Nohmi T, Hakura A, Nakai Y, Watanabe M, Murayama S Y, Sofuni T
Division of Genetics and Mutagenesis, National Institute of Hygienic Sciences, Tokyo, Japan.
J Bacteriol. 1991 Feb;173(3):1051-63. doi: 10.1128/jb.173.3.1051-1063.1991.
Expression of the umuDC operon is required for UV and most chemical mutagenesis in Escherichia coli. The DNA which can restore UV mutability to a umuD44 strain and to a umuC122::Tn5 strain of E. coli has been cloned from Salmonella typhimurium TA1538. DNA sequence analysis indicated that the cloned DNA potentially encoded proteins with calculated molecular weights of 15,523 and 47,726 and was an analog of the E. coli umuDC operon. We have termed this cloned DNA the samAB (for Salmonella mutagenesis) operon and tentatively referred to the umuDC operon of S. typhimurium LT2 (C. M. Smith, W. H. Koch, S. B. Franklin, P. L. Foster, T. A. Cebula, and E. Eisenstadt, J. Bacteriol. 172:4964-4978, 1990; S. M. Thomas, H. M. Crowne, S. C. Pidsley, and S. G. Sedgwick, J. Bacteriol. 172:4979-4987, 1990) as the umuDCST operon. The samAB operon is 40% diverged from the umuDCST operon at the nucleotide level. Among five umuDC-like operons so far sequenced, i.e., the samAB, umuDCST, mucAB, impAB, and E. coli umuDC operons, the samAB operon shows the highest similarity to the impAB operon of TP110 plasmid while the umuDCST operon shows the highest similarity to the E. coli umuDC operon. Southern hybridization experiments indicated that (i) S. typhimurium LT2 and TA1538 had both the samAB and the umuDCST operons and (ii) the samAB operon was located in a 60-MDa cryptic plasmid. The umuDCST operon is present in the chromosome. The presence of the two homologous but different umuDC operons may be involved in the poor mutability of S. typhimurium by UV and chemical mutagens.
在大肠杆菌中，紫外线诱变和大多数化学诱变都需要umuDC操纵子的表达。能够恢复大肠杆菌umuD44菌株和umuC122::Tn5菌株紫外线诱变能力的DNA已从鼠伤寒沙门氏菌TA1538中克隆出来。DNA序列分析表明，克隆的DNA可能编码分子量分别为15,523和47,726的蛋白质，并且是大肠杆菌umuDC操纵子的类似物。我们将此克隆的DNA称为samAB（用于沙门氏菌诱变）操纵子，并暂时将鼠伤寒沙门氏菌LT2的umuDC操纵子（C.M.史密斯、W.H.科赫、S.B.富兰克林、P.L.福斯特、T.A.塞布拉和E.艾森施塔特，《细菌学杂志》172:4964 - 4978，1990；S.M.托马斯、H.M.克劳恩、S.C.皮兹利和S.G.塞奇威克，《细菌学杂志》172:4979 - 4987，1990）称为umuDCST操纵子。samAB操纵子在核苷酸水平上与umuDCST操纵子有40%的差异。在目前已测序的五个类似umuDC的操纵子中，即samAB、umuDCST、mucAB、impAB和大肠杆菌umuDC操纵子，samAB操纵子与TP110质粒的impAB操纵子相似度最高，而umuDCST操纵子与大肠杆菌umuDC操纵子相似度最高。Southern杂交实验表明：（i）鼠伤寒沙门氏菌LT2和TA1538同时具有samAB和umuDCST操纵子；（ii）samAB操纵子位于一个60兆道尔顿的隐蔽质粒中。umuDCST操纵子存在于染色体中。这两个同源但不同的umuDC操纵子的存在可能与鼠伤寒沙门氏菌对紫外线和化学诱变剂诱变能力较差有关。
