Dissection of the bacteriophage T4 late promoter complex
Dissection of the bacteriophage T4 late promoter complex
复制标题
DOI：
10.1016/j.jmb.2008.03.071
复制
发表时间：
2008-06-06
影响因子：
5.6
通讯作者：
Geiduschek, E. Peter
中科院分区：
文献类型：
--
作者：
Nechaev, Sergei;Geiduschek, E. Peter
噬菌体T4晚期基因的激活转录是由一种与转录调节的常见模式不同的机制产生的：激活因子是gp45，病毒复制体的滑动钳；两种滑动夹结合蛋白gp33和gp55取代宿主RNA聚合酶（RNAP）的一个亚基。我们对滑动钳与gp33和gp55的个体相互作用进行了诱变、重新配置和选择性破坏，并监测了对转录的影响。gp33和gp55的c端滑动钳结合表位是完全可互换的，但这两种rnap -滑动钳连接的功能不同：只有gp33-gp45连接是激活所必需的，而gh55-gP45连接的缺失会损害但不会消除激活。由滑动钳激活的野生型T4 RNAP形成转录就绪启动子复合物，抵抗高浓度聚阴离子肝素的竞争。启动子复合物的快速形成需要T4晚期RNAP与滑动钳的连接。预打开启动子可以补偿gp55-gp45的缺失，但不能补偿gp33-gp45的缺失。我们用两个RNAP全酶和两个DNA模板来解释这些发现和我们之前对细菌转录起始共同模型的分析之间的关系：(1)gp55-RNAP和T4晚期启动子执行基础转录；(2) gp55-gp33-RNAP和T4晚期启动子及其移动增强子T4滑动钳执行激活转录。gp55和gp33发挥类似j的功能，gp55参与启动子识别，gp33（以及gp55）参与增强子识别。Gp33通过抑制基础转录来控制这两种途径之间的切换。(c) 2008 Elsevier Ltd.版权所有。
Activated transcription of the bacteriophage T4 late genes is generated by a mechanism that stands apart from the common modalities of transcriptional regulation: the activator is gp45, the viral replisome's sliding clamp; two sliding-clamp-binding proteins, gp33 and gp55, replace the host RNA polymerase (RNAP) a subunit. We have mutagenized, reconfigured and selectively disrupted individual interactions of the sliding clamp with gp33 and gp55 and have monitored effects on transcription. The C-terminal sliding-clamp-binding epitopes of gp33 and gp55 are perfectly interchangeable, but the functions of these two RNAP-sliding clamp connections differ: only the gp33-gp45 linkage is essential for activation, while loss of the gh55-gP45 linkage impairs but does not abolish activation. Formation of transcription-ready promoter complexes by the sliding-clamp-activated wild-type T4 RNAP resists competition by high concentrations of the polyanion heparin. This avid formation of promoter complexes requires both linkages of the T4 late RNAP to the sliding clamp. Preopening the promoter compensates for loss of the gp55-gp45 but not the gp33-gp45 linkage. We interpret the relationship of these findings and our prior analysis to the common model of transcriptional initiation in bacteria in terms of two parallel pathways, with two RNAP holoenzymes and two DNA templates: (1) gp55-RNAP and the T4 late promoter execute basal transcription; (2) gp55-gp33-RNAP and the T4 late promoter with its mobile enhancer, the T4 sliding clamp, execute activated transcription. gp55 and gp33 perform (J-like functions, gp55 in promoter recognition and gp33 (as well as gp55) in enhancer recognition. gp33 operates the switch between these two pathways by repressing basal transcription. (c) 2008 Elsevier Ltd. All rights reserved.