期刊名称:Proceedings of the National Academy of Sciences
印刷版ISSN:0027-8424
电子版ISSN:1091-6490
出版年度:2000
卷号:97
期号:24
页码:13215-13220
DOI:10.1073/pnas.97.24.13215
语种:English
出版社:The National Academy of Sciences of the United States of America
摘要:Transcriptional activators in prokaryotes have been shown to stimulate different steps in the initiation process including the initial binding of RNA polymerase (RNAP) to the promoter and a postbinding step known as the isomerization step. Evidence suggests that activators that affect initial binding can work by a cooperative binding mechanism by making energetically favorable contacts with RNAP, but the mechanism by which activators affect the isomerization step is unclear. A well-studied example of an activator that normally exerts its effect exclusively on the isomerization step is the bacteriophage {lambda} cI protein ({lambda}cI), which has been shown genetically to interact with the C-terminal region of the {sigma}70 subunit of RNAP. We show here that the interaction between {lambda}cI and {sigma} can stimulate transcription even when the relevant portion of {sigma} is transplanted to another subunit of RNAP. This activation depends on the ability of {lambda}cI to stabilize the binding of the transplanted {sigma} moiety to an ectopic -35 element. Based on these and previous findings, we discuss a simple model that explains how an activator's ability to stabilize the binding of an RNAP subdomain to the DNA can account for its effect on either the initial binding of RNAP to a promoter or the isomerization step.