@article{mbs:/content/journal/micro/10.1099/mic.0.27972-0, author = "Hinton, Deborah M. and Pande, Suchira and Wais, Neelowfar and Johnson, Xanthia B. and Vuthoori, Madhavi and Makela, Anna and Hook-Barnard, India", title = "Transcriptional takeover by σ appropriation: remodelling of the σ70 subunit of Escherichia coli RNA polymerase by the bacteriophage T4 activator MotA and co-activator AsiA", journal= "Microbiology", year = "2005", volume = "151", number = "6", pages = "1729-1740", doi = "https://doi.org/10.1099/mic.0.27972-0", url = "https://www.microbiologyresearch.org/content/journal/micro/10.1099/mic.0.27972-0", publisher = "Microbiology Society", issn = "1465-2080", type = "Journal Article", abstract = "Activation of bacteriophage T4 middle promoters, which occurs about 1 min after infection, uses two phage-encoded factors that change the promoter specificity of the host RNA polymerase. These phage factors, the MotA activator and the AsiA co-activator, interact with the σ 70 specificity subunit of Escherichia coli RNA polymerase, which normally contacts the −10 and −35 regions of host promoter DNA. Like host promoters, T4 middle promoters have a good match to the canonical σ 70 DNA element located in the −10 region. However, instead of the σ 70 DNA recognition element in the promoter's −35 region, they have a 9 bp sequence (a MotA box) centred at −30, which is bound by MotA. Recent work has begun to provide information about the MotA/AsiA system at a detailed molecular level. Accumulated evidence suggests that the presence of MotA and AsiA reconfigures protein–DNA contacts in the upstream promoter sequences, without significantly affecting the contacts of σ 70 with the −10 region. This type of activation, which is called ‘σ appropriation’, is fundamentally different from other well-characterized models of prokaryotic activation in which an activator frequently serves to force σ 70 to contact a less than ideal −35 DNA element. This review summarizes the interactions of AsiA and MotA with σ 70, and discusses how these interactions accomplish the switch to T4 middle promoters by inhibiting the typical contacts of the C-terminal region of σ 70, region 4, with the host −35 DNA element and with other subunits of polymerase.", }