Editing Sigma factor (section)

== Genes with dual sigma factor preference ==

While most genes of ''E. coli'' can be recognized by an RNAP with one and only one type of sigma factor (e.g. sigma 70), a few genes (~ 5%) have what is called a “dual sigma factor preference”,<ref name=":1">{{Cite journal |last1=Baptista |first1=Ines S.C. |last2=Kandavalli |first2=Vinodh |last3=Chauhan |first3=Vatsala |last4=Bahrudeen |first4=Mohamed N.M. |last5=Almeida |first5=Bilena L.B. |last6=Palma |first6=Cristina S.D. |last7=Dash |first7=Suchintak |last8=Ribeiro |first8=Andre S. |date=April 2022 |title=Sequence-dependent model of genes with dual σ factor preference |journal=Biochimica et Biophysica Acta (BBA) - Gene Regulatory Mechanisms |language=en |volume=1865 |issue=3 |pages=194812 |doi=10.1016/j.bbagrm.2022.194812|pmid=35338024 |s2cid=247636833 |doi-access=free |hdl=10362/143501 |hdl-access=free }}</ref> that is, they can respond to two different sigma factors, as reported in RegulonDB.<ref>{{Cite journal |last1=Santos-Zavaleta |first1=Alberto |last2=Salgado |first2=Heladia |last3=Gama-Castro |first3=Socorro |last4=Sánchez-Pérez |first4=Mishael |last5=Gómez-Romero |first5=Laura |last6=Ledezma-Tejeida |first6=Daniela |last7=García-Sotelo |first7=Jair Santiago |last8=Alquicira-Hernández |first8=Kevin |last9=Muñiz-Rascado |first9=Luis José |last10=Peña-Loredo |first10=Pablo |last11=Ishida-Gutiérrez |first11=Cecilia |date=2019-01-08 |title=RegulonDB v 10.5: tackling challenges to unify classic and high throughput knowledge of gene regulation in E. coli K-12 |url=https://academic.oup.com/nar/article/47/D1/D212/5160972 |journal=Nucleic Acids Research |language=en |volume=47 |issue=D1 |pages=D212–D220 |doi=10.1093/nar/gky1077 |issn=0305-1048 |pmc=6324031 |pmid=30395280}}</ref> The most common ones are those promoters that can respond to both sigma 70 and to sigma 38 (iIlustrated in the figure) . Studies of the dynamics of these genes showed that when the cells enter stationary growth they are almost as induced as those genes that have preference for σ38 alone. This induction level was shown to be predictable from their promoter sequence.<ref name=":1" /> A model of their dynamics is shown in the figure. In the future, these promoters may become useful tools in synthetic genetic constructs in ''E. coli''.
[[File:SigmFactModelWikipedia01A.jpg|thumb|'''Left''': illustration of genes whose promoters can be recognized by both sigma 70 (green) and sigma 38 (blue). Shown are the RNA polymerases, carrying the two different sigma factors, and either of them can bind to the promoter region (grey rectangle). '''Right''': Model proposed in [15] of these genes. The model consists of a two-step process of gene expression (transcription followed by translation). The rate constant from transcription (k<sub>t</sub>) accounts for the possibility of binding by either RNAP (those carrying sigma 70, and those carrying sigma 38). The model also includes translation (rate constant kt), and RNA and protein degradation to “nothing” represented by the “slashed zero glyph”. |401x401px|center]]