SPECIFICITY DETERMINANTS AND STRUCTURAL FEATURES IN THE RNA TARGET OF THE BACTERIAL ANTITERMINATOR PROTEINS OF THE BGLG/SACY FAMILY
SPECIFICITY DETERMINANTS AND STRUCTURAL FEATURES IN THE RNA TARGET OF THE BACTERIAL ANTITERMINATOR PROTEINS OF THE BGLG/SACY FAMILY
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DOI：
10.1073/pnas.89.21.10410
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发表时间：
1992-11-01
影响因子：
11.1
通讯作者：
STEINMETZ, M
中科院分区：
文献类型：
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作者：
AYMERICH, S;STEINMETZ, M
枯草芽孢杆菌 sacB 基因和 sacPA 操纵子以及大肠杆菌 bgl 操纵子的诱导分别由 sacY、sacT 和 bglG 基因编码的结构同源反终止子介导。当激活时，这些蛋白质可防止位于三个操纵子前导区域的终止子处的早期转录终止。先前显示 BglG 在体外与位于终止子上游并与其部分重叠的不完全回文 29 核苷酸 RNA 序列结合[Houman, F., Diaz-Torres, M. R. & Wright, A. (1990) Cell 62, 1153-1163]。在 sacB 和 sacPA 的前导序列中发现了类似的基序，此处称为核糖核酸反终止子 (RAT)，在序列和位置上高度保守。在 sacB RAT 中产生突变并在枯草芽孢杆菌中进行测试；这表明 sacB RAT 是 SacY 介导的 sacB 诱导的靶标，并且 mRNA 中的茎环结构是调节功能所必需的。增加 sacB RAT 与 sacPA 或 bgl 相似性的突变使 sacB 分别可由 SacT 或 BglG 诱导；大多数这些变化并没有强烈影响 SacY 的诱导，表明这些可变位置的核苷酸充当负特异性决定因素。
Induction of the Bacillus subtilis sacB gene and sacPA operon and Escherichia coli bgl operon is mediated by structurally homologous antiterminators encoded by the sacY, sacT, and bglG genes, respectively. When activated, these proteins prevent early transcription termination at terminators located in the leader regions of the three operons. BglG was previously shown to bind in vitro to an imperfectly palindromic 29-nucleotide RNA sequence located upstream of the terminator and partially overlapping with it [Houman, F., Diaz-Torres, M. R. & Wright, A. (1990) Cell 62, 1153-1163]. Similar motifs, here termed ribonucleic antiterminators (RATs), strongly conserved in sequence and in position, are found in the leader of both sacB and sacPA. Mutations were created in sacB RAT and tested in B. subtilis; this showed that sacB RAT is the target for SacY-mediated induction of sacB and that a stem-loop structure in the mRNA is required for regulatory function. Mutations increasing the similarity of the sacB RAT with those of sacPA or bgl rendered sacB inducible by SacT or BglG, respectively; most of these changes did not strongly affect induction by SacY, suggesting that the nucleotides at these variable positions act as negative specificity determinants.