Small RNA-induced differential degradation of the polycistronic mRNA iscRSUA.
Most polycistronic genes are expressed in a single transcript, in which each cistron produces a fixed amount of protein. In this report, we show the first example of differential degradation of a polycistronic gene induced by a small regulatory RNA (sRNA). Our data show that the iron-responsive sRNA, RyhB, binds to the second cistron of the polycistronic mRNA, iscRSUA, which encodes the necessary machinery for biosynthesis of Fe-S clusters, and promotes the cleavage of the downstream iscSUA transcript. This cleavage gives rise to the remaining 5'-section of the transcript encoding IscR, a transcriptional regulator responsible for activation and repression of several genes depending on the cellular Fe-S level. Our data indicate that the iscR transcript is stable and that translation is active. The stability of the iscR transcript depends on a 111-nucleotide long non-translated RNA section located between iscR and iscS, which forms a strong repetitive extragenic palindromic secondary structure and may protect against ribonucleases degradation. This novel regulation shows how sRNAs and mRNA structures can work together to modulate the transcriptional response to a specific stress.
Desnoyers
Guillaume
G
Département de Biochimie, Groupe ARN, Université de Sherbrooke, Sherbrooke, Québec, Canada.
Morissette
Audrey
A
Prévost
Karine
K
Massé
Eric
E
D004926:Escherichia coli / Q000502:physiology; D029968:Escherichia coli Proteins / Q000096:biosynthesis*; D015964:Gene Expression Regulation, Bacterial; D007501:Iron / Q000378:metabolism*; D008954:Models, Biological; D008958:Models, Molecular; D009690:Nucleic Acid Conformation; D020871:RNA Stability; D034741:RNA, Small Interfering / Q000378:metabolism*; D013455:Sulfur / Q000378:metabolism*; D014157:Transcription Factors / Q000096:biosynthesis*
D029968:Escherichia coli Proteins; C499695:IscR protein, E coli; D034741:RNA, Small Interfering; D014157:Transcription Factors; D013455:Sulfur; D007501:Iron