RNAIII

{{short description|Small RNA}}

RNAIII is a stable 514 nt regulatory RNA transcribed by the P3 promoter of the Staphylococcus aureus quorum-sensing agr system {{cite journal | vauthors = Novick RP, Ross HF, Projan SJ, Kornblum J, Kreiswirth B, Moghazeh S | title = Synthesis of staphylococcal virulence factors is controlled by a regulatory RNA molecule | journal = The EMBO Journal | volume = 12 | issue = 10 | pages = 3967–75 | date = October 1993 | pmid = 7691599 | pmc = 413679 | doi = 10.1002/j.1460-2075.1993.tb06074.x}}{{cite journal | vauthors = Waters LS, Storz G | title = Regulatory RNAs in bacteria | journal = Cell | volume = 136 | issue = 4 | pages = 615–28 | date = February 2009 | pmid = 19239884 | pmc = 3132550 | doi = 10.1016/j.cell.2009.01.043 }}). It is the major effector of the agr regulon, which controls the expression of many S. aureus genes encoding exoproteins and cell wall associated proteins plus others encoding regulatory proteins {{cite journal | vauthors = Janzon L, Arvidson S | title = The role of the delta-lysin gene (hld) in the regulation of virulence genes by the accessory gene regulator (agr) in Staphylococcus aureus | journal = The EMBO Journal | volume = 9 | issue = 5 | pages = 1391–9 | date = May 1990 | pmid = 2328718 | pmc = 551825 | doi = 10.1002/j.1460-2075.1990.tb08254.x}}{{cite journal | vauthors = Novick RP | title = Autoinduction and signal transduction in the regulation of staphylococcal virulence | journal = Molecular Microbiology | volume = 48 | issue = 6 | pages = 1429–49 | date = June 2003 | pmid = 12791129 | doi = 10.1046/j.1365-2958.2003.03526.x | s2cid = 6847208 | doi-access = free }} The RNAIII transcript also encodes the 26 amino acid δ-haemolysin (Staphylococcus aureus delta toxin) peptide (Hld).{{cite journal | vauthors = Benito Y, Kolb FA, Romby P, Lina G, Etienne J, Vandenesch F | title = Probing the structure of RNAIII, the Staphylococcus aureus agr regulatory RNA, and identification of the RNA domain involved in repression of protein A expression | journal = RNA | volume = 6 | issue = 5 | pages = 668–79 | date = May 2000 | pmid = 10836788 | pmc = 1369947 | doi = 10.1017/S1355838200992550 }} RNAIII contains many stem loops, most of which match the Shine-Dalgarno sequence involved in translation initiation of the regulated genes. Some of these interactions are inhibitory, others stimulatory; among the former is the regulatory protein Rot.{{cite journal | vauthors = Geisinger E, Adhikari RP, Jin R, Ross HF, Novick RP | title = Inhibition of rot translation by RNAIII, a key feature of agr function | journal = Molecular Microbiology | volume = 61 | issue = 4 | pages = 1038–48 | date = August 2006 | pmid = 16879652 | doi = 10.1111/j.1365-2958.2006.05292.x | s2cid = 229424 | doi-access = free }}{{cite journal | vauthors = Boisset S, Geissmann T, Huntzinger E, Fechter P, Bendridi N, Possedko M, Chevalier C, Helfer AC, Benito Y, Jacquier A, Gaspin C, Vandenesch F, Romby P | display-authors = 6 | title = Staphylococcus aureus RNAIII coordinately represses the synthesis of virulence factors and the transcription regulator Rot by an antisense mechanism | journal = Genes & Development | volume = 21 | issue = 11 | pages = 1353–66 | date = June 2007 | pmid = 17545468 | pmc = 1877748 | doi = 10.1101/gad.423507 }} In vitro, RNAIII is expressed post exponentially, inhibiting translation of the surface proteins, notably protein A, while stimulating that of the exoproteins, many of which are tissue-degrading enzymes or cytolysins.{{cite journal | vauthors = Dunman PM, Murphy E, Haney S, Palacios D, Tucker-Kellogg G, Wu S, Brown EL, Zagursky RJ, Shlaes D, Projan SJ | display-authors = 6 | title = Transcription profiling-based identification of Staphylococcus aureus genes regulated by the agr and/or sarA loci | journal = Journal of Bacteriology | volume = 183 | issue = 24 | pages = 7341–53 | date = December 2001 | pmid = 11717293 | pmc = 95583 | doi = 10.1128/JB.183.24.7341-7353.2001 }} Among the latter is the important virulence factor, α-hemolysin (or alpha toxin) (Hla), whose translation RNAIII activates by preventing the formation of an inhibitory foldback loop in the hla mRNA leader.{{cite journal | vauthors = Morfeldt E, Taylor D, von Gabain A, Arvidson S | title = Activation of alpha-toxin translation in Staphylococcus aureus by the trans-encoded antisense RNA, RNAIII | journal = The EMBO Journal | volume = 14 | issue = 18 | pages = 4569–77 | date = September 1995 | doi = 10.1002/j.1460-2075.1995.tb00136.x | pmid = 7556100 | pmc = 394549 }}