Regulation of bacteriophage λ int gene expression
Regulation of bacteriophage λ int gene expression
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噬菌体 λ int 基因表达的调控
DOI：
10.1016/0022-2836(82)90201-7
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发表时间：
1982
影响因子：
5.6
通讯作者：
M. Gottesman
中科院分区：
文献类型：
--
作者：
A. Oppenheim;S. Gottesman;M. Gottesman
λ噬菌体的int基因可以在cII产物存在的情况下从pI转录，或者在N产物存在的情况下从pL转录。在感染时，Int仅由pI表达，而在诱导的原噬菌体中，Int可以由pL表达。关键的区别是b+区域，它与感染噬菌体相邻，但在原噬菌体中是分开的。当构建的前噬菌体中b+与int相邻时，pL控制下的Int合成受到强烈抑制。我们构建了lacZ-pI和lacZ-pL融合体，其中融合体位于b区域内attP位点左侧252个碱基对处。这些融合使我们能够分析各种突变对 cII 激活 pI 的能力和 theint 基因表达的影响。我们发现 lacZfrompL 的表达发生在 b53 缺失（-252 个碱基对到 -160 个碱基对）中，但不在野生型噬菌体中表达。因此，b53 缺失去除了 tI 终止子。它还删除了包含这些突变的区域（Guarneros & Galindo，1979）；正如预期的那样，它允许在感染期间表达 intfrompL。 tI 终止子被作用于 pL 转录的 N 功能抑制，并且在 arho15 突变体中具有活性。cII 独立的 pI 突变 pintc226 作为弱启动子，不受 cII 进一步刺激。由于intc226在-11处是G·C到A·T的变化，这表明pI和cII产物之间的相互作用可能涉及该启动子的Pribnow盒区域中的序列。我们发现pI在携带himA或hipmutations的宿主中不被激活，并且我们已经证明这是由于这些宿主突变体中cII产物合成的失败。我们的结果证实了基于转录本特异性终止子的Int表达逆向调节的一般模型thebregion（Guarneroset al.，1982）。
Theintgene of bacteriophage lambda can be transcribed frompIin the presence ofcII product or frompLin the presence ofNproduct. On infection Int is expressed only frompI, while in an induced prophage Int can be expressed frompL. The critical difference is theb+region, which is adjacent tointin an infecting phage, but is separate in a prophage. When a prophage is constructed in whichb+is adjacent toint, the synthesis of Int underpLcontrol is strongly inhibited.We have constructedlacZ-pIandlacZ-pLfusions, where the fusion is 252 basepairs to the left of theattP site, within thebregion. These fusions permit us to analyze the effects of various mutations on the ability ofcII to activatepIand on the expression of theintgene. We find that the expression oflacZfrompLtakes place in theb53 deletion (−252 base-pairs to −160 base-pairs) but not in wild-type phage. Theb53 deletion thus removes thetIterminator. It also removes the region containing thesibmutations (Guarneros & Galindo, 1979); as expected, it permits the expression ofintfrompLduring infection. ThetIterminator is suppressed byN-function acting on transcription frompL, and is active in arho15 mutant.ThecII-independentpImutationpintc226acts as a weak promoter which is not further stimulated bycII. Sinceintc226 is a G · C to A · T change at −11, this suggests that the interaction betweenpIandcII product may involve sequences in the Pribnow box region of this promoter.We have found thatpIis not activated in hosts carrying thehimAorhipmutations, and we have demonstrated that this is due to the failure ofcII product synthesis in these host mutants.Our results substantiate the general model of retroregulation of Int expression based on a transcript-specific terminator in thebregion (Guarneroset al., 1982).