Colonna B, Bernardini M, Micheli G, Maimone F, Nicoletti M, Casalino M
Dipartimento di Biologia Cellulare e dello Sviluppo, Universitá di Roma La Sapienza, Italy.
Plasmid. 1988 Nov;20(3):221-31. doi: 10.1016/0147-619x(88)90028-5.
Tn1935, a 23.5-kb transposon mediating resistance to ampicillin, kanamycin, mercury, spectinomycin, and sulfonamide was isolated from pZM3, an IncFIme virulence plasmid from Salmonella wien. Tn1935 possesses the entire sequence of Tn21 and contains two additional DNA segments of 0.95 and 2.7 kb carrying the ampicillin and kanamycin resistance genes, respectively. The latter is part of a composite element since it is flanked by two IS15-like insertion sequences (IS1936) in direct orientation. IS1936 is about 800 bp long and is closely related to IS15 delta, IS26, IS46, IS140, and IS176. Functional analysis of IS1936-mediated cointegrates shows that both insertion sequences are active and able to form cointegrates at the same frequency. Resolution of the cointegrates requires the presence of the host Rec system. The presence of the composite IS1936-element within Tn1935 supports the hypothesis that multidrug resistance transposons evolved by insertion of antibiotic determinants which are themselves transposable.
Tn1935是一个23.5千碱基对的转座子，介导对氨苄青霉素、卡那霉素、汞、壮观霉素和磺胺类药物的抗性，它是从pZM3中分离得到的，pZM3是来自维也纳沙门氏菌的一种IncFI型毒力质粒。Tn1935拥有Tn21的完整序列，并包含另外两个分别携带氨苄青霉素和卡那霉素抗性基因的0.95千碱基对和2.7千碱基对的DNA片段。后者是一个复合元件的一部分，因为它两侧是两个同向的IS15样插入序列（IS1936）。IS1936长约800碱基对，与IS15δ、IS26、IS46、IS140和IS176密切相关。对IS1936介导的共整合体的功能分析表明，两个插入序列都是活跃的，并且能够以相同频率形成共整合体。共整合体的解离需要宿主Rec系统的存在。Tn1935中复合IS1936元件的存在支持了这样一种假说，即多药抗性转座子是通过插入本身可转座的抗生素决定簇而进化而来的。
