Polard P, Prère M F, Chandler M, Fayet O
Centre de Recherche en Biochimie et Génétique Cellulaire, CNRS Toulouse, France.
J Mol Biol. 1991 Dec 5;222(3):465-77. doi: 10.1016/0022-2836(91)90490-w.
The proteins expressed by insertion sequence IS911, a member of the widespread IS3 family of elements, have been analyzed. The results indicate that three major species are produced from two consecutive reading frames. A protein of Mr 11,500, ORFA, is synthesized from an upstream reading frame. A larger protein, ORFAB, uses the same initiation codon and is produced by a -1 programmed translational frameshift between orfA and a downstream frame, orfB, whose amino acid sequence shows significant homology with retroviral integrase proteins. The orfB frame is also expressed independently in two alternative forms: the first uses a rare AUU initiation codon in the orfB phase whereas the second appears to initiate in the orfA phase and is produced by a -1 frameshift mechanism similar to that used in ORFAB expression. A specific IS911 integration reaction using a minimal active junction composed of 51 base-pairs of the right inverted repeat and a flanking phase lambda sequence resembling a second end in inverted orientation has been developed to analyze the functions of these proteins by transcomplementation in vivo. The orfA and orfB frames are shown to be essential and production of ORFAB is shown to stimulate integration in this system, suggesting that this fusion protein is the IS911 transposase.
对广泛存在的IS3元件家族成员插入序列IS911所表达的蛋白质进行了分析。结果表明，从两个连续的阅读框产生了三种主要的蛋白质。11,500的蛋白质ORFA由上游阅读框合成。一种更大的蛋白质ORFAB使用相同的起始密码子，并且是通过orfA与下游阅读框orfB之间的-1程序性翻译移码产生的，其氨基酸序列与逆转录病毒整合酶蛋白具有显著同源性。orfB阅读框也以两种替代形式独立表达：第一种在orfB阶段使用罕见的AUU起始密码子，而第二种似乎在orfA阶段起始，并通过与ORFAB表达中使用的机制类似的-1移码机制产生。已经开发出一种使用由51个碱基对的右侧反向重复序列和类似反向第二个末端的侧翼λ序列组成的最小活性连接体的特异性IS911整合反应，以通过体内反式互补分析这些蛋白质的功能。结果表明，orfA和orfB阅读框是必需的，并且在该系统中ORFAB的产生刺激了整合，这表明这种融合蛋白是IS911转座酶。
