FnrS RNA is a family of Hfq-binding small RNA whose expression is upregulated in response to anaerobic conditions. It is named FnrS because its expression is strongly dependent on fumarate and nitrate reductase regulator (FNR), a direct oxygen availability sensor.[1][2]
A conserved intergenic region between genes ydaN and dbpA was predicted to encode an sRNA, adjacent to where another non-coding RNA (C0343) has been identified.[3] However, northern blot analysis of this 477bp sequence yielded no results.[4] A subsequent tiling array analysis sequencing Hfq-binding sRNA found that the Watson strand did indeed encode an sRNA.[1]
A study incorporating comparative target prediction and subsequent experimental verification of selected predictions, suggests that FnrS might be a more global regulator in Escherichia coli. It is predicted to control several transcription factors. These include the verified targets marA and IscR.[9] MarA activates genes involved in the resistance to superoxide,[10] which might not be necessary at the anaerobic conditions where FnrS is expressed. IscR regulates genes for iron-sulfur-cluster containing or biogenesis proteins.[11] FnrS might be involved in the observed O2 dependent expression of the IscR regulon.[11] Further targets of FnrS are nagZ and sdhA.[9]
There is also evidence to suggest that the expression of FnrS is regulated by the RcsCDB signalling system in Salmonella enterica.[12]
^ abGiel JL, Rodionov D, Liu M, Blattner FR, Kiley PJ (2006). "IscR-dependent gene expression links iron-sulphur cluster assembly to the control of O2-regulated genes in Escherichia coli". Mol Microbiol. 60 (4): 1058–1075. doi:10.1111/j.1365-2958.2006.05160.x. PMID16677314. S2CID16807119.
^Paradela A, Mariscotti JF, Navajas R, Ramos-Fernández A, Albar JP, García-Del Portillo F (2011). "Inverse regulation in the metabolic genes pckA and metE revealed by proteomic analysis of the Salmonella RcsCDB regulon". J Proteome Res. 10 (8): 3386–3398. doi:10.1021/pr101294v. PMID21657791.
