Orientational control of fimE expression in Escherichia coli.
Orientational control of fimE expression in Escherichia coli.
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大肠杆菌中 fimE 表达的定向控制。
DOI：
10.1046/j.1365-2958.2001.02655.x
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发表时间：
2001
影响因子：
3.6
通讯作者：
Blomfield,IC
中科院分区：
文献类型：
--
作者：
Sohanpal,BK;Kulasekara,HD;Bonnen,A;Blomfield,IC
1 型菌毛的相变表达部分是由大肠杆菌中 fimswitch 的位点特异性 DNA 反转控制的。在催化反转反应的两种 fim 重组酶（FimB 和 FimE）中，FimE 对从 ON 方向到 OFF 方向的相转换表现出强烈的偏差。与 fimE 相关的特异性是两种不同机制的结果：（i）FimE 表现出对 ON 方向的可逆元件作为重组底物的偏好； (ii) OFF方向的可逆元件顺式作用抑制重组酶活性（方向控制）。我们在此表明，尽管 afimE-lacZYA 转录融合的表达不受方向控制的影响，但可逆元件对 fimE 进行负调控。 fimEtranscript 延伸到可逆区域，因此开关 ON 特异性和开关 OFF 特异性 mRNA 包含不同的序列。此外，我们发现在 fimE 和 fimswitch 之间插入结构化 RNA (tRNAGly) 可以抑制方向控制，这表明开关 OFF 特异性 mRNA 通过 3' 至 5' 降解而失活。对 fimswitch 的分析表明，它包含两个独立发挥方向控制作用的抑制元件。
Phase‐variable expression of type 1 fimbriae is, in part, controlled by site‐specific DNA inversion of thefimswitch inEscherichia coli.Of the twofimrecombinases (FimB and FimE) that catalyse the inversion reaction, FimE exhibits a strong bias for phase switching from the ON to the OFF orientation. The specificity associated withfimEis the result of two different mechanisms: (i) FimE exhibits a preference for the invertible element in the ON orientation as substrate for recombination; (ii) the invertible element in the OFF orientation actsin cisto inhibit recombinase activity (orientational control). We show here that the invertible element negatively regulatesfimE, even though expression of afimE–lacZYAtranscriptional fusion is unaffected by orientational control. ThefimEtranscript extends into the invertible region and hence switch ON‐specific and switch OFF‐specific mRNA contain different sequences. Furthermore, we show that orientational control is suppressed by the insertion of a structured RNA (tRNAGly) betweenfimEand thefimswitch, indicating that the switch OFF‐specific mRNA is inactivated by 3′ to 5′ degradation. Analysis of thefimswitch reveals that it contains two inhibitory elements that exert orientational control independently.