Conservation and diversity in the immunity regions of wild phages with the immunity specificity of phage λ
Conservation and diversity in the immunity regions of wild phages with the immunity specificity of phage λ
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DOI：
10.1111/j.1365-2958.2007.05650.x
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发表时间：
2007-04-01
影响因子：
3.6
通讯作者：
Little, John W.
中科院分区：
文献类型：
--
作者：
Degnan, Patrick H.;Michalowski, Christine B.;Little, John W.
噬菌体 lambda 的基因调控回路是人们最了解的回路之一。大部分电路以免疫区域为中心，其中包括两种阻遏蛋白 Cl 和 Cro 的基因及其顺式作用位点。相关的噬菌体，称为羔羊噬菌体，具有不同的免疫区域，但与拉姆达噬菌体相似的调节电路和基因组组织，并显示出由羔羊噬菌体之间重组产生的镶嵌组织。我们对几种具有 lambda 免疫特异性的野生噬菌体的免疫区域进行了测序，以确定调节中是否存在自然变异，并分析富含经过充分研究的调节元件的区域的保守性和变异性。 Cl、Cro及其顺式作用位点与lambda中的几乎相同，这意味着免疫区域控制的调节机制是保守的。与操作者区域之一相邻的片段也被保留，并且可能是一种新颖的调节元件。在大多数分离株中，两种调节蛋白（N 和 CII）的不同等位基因位于免疫区域的侧翼；分离株之间的裂解-溶源决定可能变化更大。在免疫区域侧翼的几个元件中观察到广泛的镶嵌现象。还鉴定了非常短的序列元件或微同源性。我们的研究结果表明了精细镶嵌现象的产生机制。
The gene regulatory circuitry of phage lambda is among the best-understood circuits. Much of the circuitry centres around the immunity region, which includes genes for two repressors, Cl and Cro, and their cis-acting sites. Related phages, termed lambdoid phages, have different immunity regions, but similar regulatory circuitry and genome organization to that of lambda, and show a mosaic organization, arising by recombination between lambdoid phages. We sequenced the immunity regions of several wild phages with the immunity specificity of lambda, both to determine whether natural variation exists in regulation, and to analyse conservation and variability in a region rich in well-studied regulatory elements. Cl, Cro and their cis-acting sites are almost identical to those in lambda, implying that regulatory mechanisms controlled by the immunity region are conserved. A segment adjacent to one of the operator regions is also conserved, and may he a novel regulatory element. In most isolates, different alleles of two regulatory proteins (N and CII) flank the immunity region; possibly the lysis-lysogeny decision is more variable among isolates. Extensive mosaicism was observed for several elements flanking the immunity region. Very short sequence elements or microhomologies were also identified. Our findings suggest mechanisms by which fine-scale mosaicism arises.