Department of Biological Sciences, University at Buffalo, the State University of New York, Buffalo, New York 14260, USA.
Nucleic Acids Res. 2011 Mar;39(6):2092-102. doi: 10.1093/nar/gkq965. Epub 2010 Nov 21.
The Bacillus subtilis trpEDCFBA operon is regulated by a transcription attenuation mechanism controlled by the trp RNA-binding attenuation protein (TRAP). TRAP binds to 11 (G/U)AG repeats in the trp leader transcript and prevents formation of an antiterminator, which allows formation of an intrinsic terminator (attenuator). Previously, formation of the attenuator RNA structure was believed to be solely responsible for signaling RNA polymerase (RNAP) to halt transcription. However, base substitutions that prevent formation of the antiterminator, and thus allow the attenuator structure to form constitutively, do not result in efficient transcription termination. The observation that the attenuator requires the presence of TRAP bound to the nascent RNA to cause efficient transcription termination suggests TRAP has an additional role in causing termination at the attenuator. We show that the trp attenuator is a weak intrinsic terminator due to low GC content of the hairpin stem and interruptions in the U-stretch following the hairpin. We also provide evidence that termination at the trp attenuator requires forward translocation of RNA polymerase and that TRAP binding to the nascent transcript can induce this activity.
枯草芽孢杆菌 trpEDCFBA 操纵子受转录衰减机制调控，该机制受色氨酸 RNA 结合衰减蛋白（TRAP）控制。TRAP 与色氨酸前导转录物中的 11 个（G/U）AG 重复序列结合，阻止终止子形成，从而允许形成内在终止子（衰减子）。此前，衰减子 RNA 结构的形成被认为是唯一负责向 RNA 聚合酶（RNAP）发出停止转录信号的因素。然而，阻止终止子形成的碱基替换，从而使衰减子结构持续形成，并不会导致有效的转录终止。观察到衰减子需要与新生 RNA 结合的 TRAP 才能导致有效的转录终止，这表明 TRAP 在衰减子处具有额外的终止作用。我们表明，由于发夹茎的 GC 含量低以及发夹后的 U 链中断，trp 衰减子是一个弱的内在终止子。我们还提供了证据表明，在 trp 衰减子时需要 RNA 聚合酶的前向移位，并且 TRAP 与新生转录本的结合可以诱导这种活性。
