The Molecular Switch of Telomere Phages: High Binding Specificity of the PY54 Cro Lytic Repressor to a Single Operator Site.
The Molecular Switch of Telomere Phages: High Binding Specificity of the PY54 Cro Lytic Repressor to a Single Operator Site.
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DOI：
10.3390/v7062746
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发表时间：
2015-06-02
期刊：
影响因子：
--
通讯作者：
Hertwig S
中科院分区：
文献类型：
--
作者：
Hammerl JA;Roschanski N;Lurz R;Johne R;Lanka E;Hertwig S
温和型噬菌体具有调节溶解性和溶原性生长的分子开关。温和端粒p5 N15、PY 54和p5 KO 2的基因组具有包含原噬菌体阻遏物、裂解阻遏物和推定的抗终止子的基因的初级免疫区（immB）。这些产物的作用被认为分别类似于λ蛋白Cl、Cro和Q的作用。此外，在原型端粒噬菌体N15和NIKO 2中的基因顺序和几个操纵位点的位置也让人联想到类端粒。相比之下，计算机模拟分析显示在PY 54中仅存在一个操纵子（OR 3）。将纯化的PY 54 Cro蛋白用于EMSA研究，证明其仅结合原噬菌体阻遏物基因上游的16-bp回文位点（OR 3）。PY 54和PK 02/N15的0 R3操纵基因序列仅在它们的外周碱基对上不同，这是Cro特异性的原因。PY 54 cI和cro转录受高活性启动子调控，启动同源无前导mRNA的合成。PY 54 Cro结合位点和已鉴定的启动子的位置表明，裂解阻遏物抑制cI转录，但不抑制其自身的合成。结果表明，一个意想不到的多样性的生长调节机制，在拟南芥相关的拟南芥。
Temperate bacteriophages possess a molecular switch, which regulates the lytic and lysogenic growth. The genomes of the temperate telomere phages N15, PY54 and ϕKO2 harbor a primary immunity region (immB) comprising genes for the prophage repressor, the lytic repressor and a putative antiterminator. The roles of these products are thought to be similar to those of the lambda proteins CI, Cro and Q, respectively. Moreover, the gene order and the location of several operator sites in the prototype telomere phage N15 and in ϕKO2 are also reminiscent of lambda-like phages. By contrast, in silico analyses revealed the presence of only one operator (OR3) in PY54. The purified PY54 Cro protein was used for EMSA studies demonstrating that it exclusively binds to a 16-bp palindromic site (OR3) upstream of the prophage repressor gene. The OR3 operator sequences of PY54 and ϕKO2/N15 only differ by their peripheral base pairs, which are responsible for Cro specificity. PY54 cI and cro transcription is regulated by highly active promoters initiating the synthesis of a homogenious species of leaderless mRNA. The location of the PY54 Cro binding site and of the identified promoters suggests that the lytic repressor suppresses cI transcription but not its own synthesis. The results indicate an unexpected diversity of the growth regulation mechanisms in lambda-related phages.
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