IGEM:Imperial/2010/sigma54

use of sigma 54 as transcription factor
What is a sigma factor?
 * prokaryotic transcription initiation factor
 * enables binding of RNA polymerase to gene promoter
 * activation dependent on different environmental conditions

In E.coli
 * sigma54
 * sigma70

sigma 54 versus sigma70
 * There is limited amino-acid similarity between sigma54 and sigma70.
 * sigma70
 * 1) sigma70-RNAP: positive and negative regulation
 * 2) transcribes most housekeeping genes
 * 3) RNAP–70 holoenzyme is competent for transcription


 * sigma54
 * 1) sigma54-RNAP: positive regulation
 * 2) controls transcription of genes expressed under specific environmental conditions
 * 3) RNAP–54 complex binds to promoter DNA, but remains stalled and unable to transcribe. When the activator protein PspF binds to a bacterial enhancer-like sequence in the promoter and hydrolyses ATP, the RNAP–54 complex is converted from a closed to an open complex that can actively transcribe. Activation of RNAP–54 transcription by PspF (activator protein) is analogous to activation of RNA polymerase II-mediated transcription in eukaryotes by the ATP-hydrolysing protein TFIIH.[]
 * 4) less basal transcription which means less noise.[]

References
 * 1) http://www.sciencedirect.com/science?_ob=MImg&_imagekey=B6WSR-4TVSH9K-5-1&_cdi=7053&_user=217827&_pii=S1097276508006916&_orig=search&_coverDate=11%2F07%2F2008&_sk=999679996&view=c&wchp=dGLzVtz-zSkzk&md5=c52f52f0737fbd12b741713839e1aed8&ie=/sdarticle.pdf
 * 2) http://jb.asm.org/cgi/reprint/181/24/7558