DsrA RNA is a non-coding RNA that regulates both transcription, by overcoming transcriptional silencing by the nucleoid-associated H-NS protein, and translation, by promoting efficient translation of the stress sigma factor, RpoS. These two activities of DsrA can be separated by mutation: the first of three stem-loops of the 85 nucleotide RNA is necessary for RpoS translation but not for anti-H-NS action, while the second stem-loop is essential for antisilencing and less critical for RpoS translation. The third stem-loop, which behaves as a transcription terminator, can be substituted by the trp transcription terminator without loss of either DsrA function. The sequence of the first stem-loop of DsrA is complementary with the upstream leader portion of RpoS messenger RNA, suggesting that pairing of DsrA with the RpoS message might be important for translational regulation. The structures of DsrA and DsrA/rpoS complex were studied by NMR. The study concluded that the sRNA contains a dynamic conformational equilibrium for its second stem–loop which might be an important mechanism for DsrA to regulate the translations of its multiple target mRNAs.
The gcvB RNA gene encodes a small non-coding RNA involved in the regulation of a number of amino acid transport systems as well as amino acid biosynthetic genes. The GcvB gene is found in enteric bacteria such as Escherichia coli. GcvB regulates genes by acting as an antisense binding partner of the mRNAs for each regulated gene. This binding is dependent on binding to a protein called Hfq. Transcription of the GcvB RNA is activated by the adjacent GcvA gene and repressed by the GcvR gene. A deletion of GcvB RNA from Y. pestis changed colony shape as well as reducing growth. It has been shown by gene deletion that GcvB is a regulator of acid resistance in E. coli. GcvB enhances the ability of the bacterium to survive low pH by upregulating the levels of the alternate sigma factor RpoS. A polymeric form of GcvB has recently been identified. Interaction of GcvB with small RNA SroC triggers the degradation of GcvB by RNase E, lifting the GcvB-mediated mRNA repression of its target genes.
The OmrA-B RNA gene family is a pair of homologous OmpR-regulated small non-coding RNA that was discovered in E. coli during two large-scale screens. OmrA-B is highly abundant in stationary phase, but low levels could be detected in exponentially growing cells as well. RygB is adjacent to RygA a closely related RNA. These RNAs bind to the Hfq protein and regulate gene expression by antisense binding. They negatively regulate the expression of several genes encoding outer membrane proteins, including cirA, CsgD, fecA, fepA and ompT by binding in the vicinity of the Shine-Dalgarno sequence, suggesting the control of these targets is dependent on Hfq protein and RNase E. Taken together, these data suggest that OmrA-B participates in the regulation of outer membrane composition, responding to environmental conditions.
The MicC non-coding RNA is located between the ompN and ydbK genes in E. coli. This Hfq-associated RNA is thought to be a regulator of the expression level of the OmpC porin protein, with a 5′ region of 22 nucleotides potentially forming an antisense interaction with the ompC mRNA. Along with MicF RNA this family may act in conjunction with EnvZ-OmpR two-component system to control the OmpF/OmpC protein ratio in response to a variety of environmental stimuli. The expression of micC was shown to be increased in the presence of beta-lactam antibiotics.
OxyS RNA is a small non-coding RNA which is induced in response to oxidative stress in Escherichia coli. This RNA acts as a global regulator to activate or repress the expression of as many as 40 genes, by an antisense mechanism, including the fhlA-encoded transcriptional activator and the rpoS-encoded sigma(s) subunit of RNA polymerase. OxyS is bound by the Hfq protein, that increases the OxyS RNA interaction with its target messages. Binding to Hfq alters the conformation of OxyS. The 109 nucleotide RNA is thought to be composed of three stem-loops.
The RprA RNA gene encodes a 106 nucleotide regulatory non-coding RNA. Translational regulation of the stationary phase sigma factor RpoS is mediated by the formation of a double-stranded RNA stem-loop structure in the upstream region of the rpoS messenger RNA, occluding the translation initiation site.
RydC is a bacterial non-coding RNA. RydC is thought to regulate a mRNA, yejABEF, which encodes an ABC transporter protein. RydC is known to bind the Hfq protein, which causes a conformational change in the RNA molecule. The Hfq/RydC complex is then thought to bind to the target mRNA and induce its degradation.
The SdsR/RyeB RNA is a non-coding RNA that was identified in a large scale screen of E. coli. The exact 5′ and 3′ ends of this RNA are uncertain. This RNA overlaps the SraC/RyeA RNA on the opposite strand suggesting that the two may act in a concerted manner. It is transcribed by general stress factor σs and is most highly expressed in stationary phase. SdsR/RyeB RNA interacts with Hfq.
The CyaR RNA non-coding RNA was identified in a large scale screen of Escherichia coli and was called candidate 14. The exact 5′ and 3′ ends of this RNA are uncertain. This gene lies between yegQ and orgK in E. coli. This small RNA was shown to be bound by the Hfq protein. This RNA has been renamed as CyaR for. It has been shown that the CyaR RNA acts as a repressor of the porin OmpX. It has also been shown that cyaR expression is tightly controlled by the cyclic AMP receptor protein, CRP.
RyhB RNA is a 90 nucleotide RNA that down-regulates a set of iron-storage and iron-using proteins when iron is limiting; it is itself negatively regulated by the ferric uptake repressor protein, Fur.
The MicA RNA is a small non-coding RNA that was discovered in E. coli during a large scale screen. Expression of SraD is highly abundant in stationary phase, but low levels could be detected in exponentially growing cells as well.
In molecular biology the ArcZ RNA is a small non-coding RNA (ncRNA). It is the functional product of a gene which is not translated into protein. ArcZ is an Hfq binding RNA that functions as an antisense regulator of a number of protein coding genes.
The sroB RNA is a non-coding RNA gene of 90 nucleotides in length. sroB is found in several Enterobacterial species but its function is unknown. SroB is found in the intergenic region on the opposite strand to the ybaK and ybaP genes. SroB is expressed in stationary phase. Experiments have shown that SroB is a Hfq binding sRNA.
The GlmY RNA family consists of a number of bacterial RNA genes of around 167 bases in length. The GlmY RNA gene is present in Escherichia coli, Shigella flexneri, Yersinia pestis and Salmonella species, where it is found between the yfhK and purL genes. It was originally predicted in a bioinformatic screen for novel ncRNAs in E. coli.
The Hfq protein encoded by the hfq gene was discovered in 1968 as an Escherichia coli host factor that was essential for replication of the bacteriophage Qβ. It is now clear that Hfq is an abundant bacterial RNA binding protein which has many important physiological roles that are usually mediated by interacting with Hfq binding sRNA.
Invasion gene associated RNA is a small non-coding RNA involved in regulating one of the major outer cell membrane porin proteins in Salmonella species.
An Hfq binding sRNA is an sRNA that binds the bacterial RNA binding protein called Hfq. A number of bacterial small RNAs which have been shown to bind to Hfq have been characterised . Many of these RNAs share a similar structure composed of three stem-loops. Several studies have expanded this list, and experimentally validated a total of 64 Hfq binding sRNA in Salmonella Typhimurium. A transcriptome wide study on Hfq binding sites in Salmonella mapped 126 Hfq binding sites within sRNAs. Genomic SELEX has been used to show that Hfq binding RNAs are enriched in the sequence motif 5′-AAYAAYAA-3′. Genome-wide study identified 40 candidate Hfq-dependent sRNAs in plant pathogen Erwinia amylovora. 12 of them were confirmed by Northern blot.
MicX sRNA is a small non-coding RNA found in Vibrio cholerae. It was given the name MicX as it has a similar function to MicA, MicC and MicF in E. coli. MicX sRNA negatively regulates an outer membrane protein and also a component of an ABC transporter. These interactions were predicted and then confirmed using a DNA microarray.
Bacterial small RNAs (bsRNA) are small RNAs produced by bacteria; they are 50- to 500-nucleotide non-coding RNA molecules, highly structured and containing several stem-loops. Numerous sRNAs have been identified using both computational analysis and laboratory-based techniques such as Northern blotting, microarrays and RNA-Seq in a number of bacterial species including Escherichia coli, the model pathogen Salmonella, the nitrogen-fixing alphaproteobacterium Sinorhizobium meliloti, marine cyanobacteria, Francisella tularensis, Streptococcus pyogenes, the pathogen Staphylococcus aureus, and the plant pathogen Xanthomonas oryzae pathovar oryzae. Bacterial sRNAs affect how genes are expressed within bacterial cells via interaction with mRNA or protein, and thus can affect a variety of bacterial functions like metabolism, virulence, environmental stress response, and structure.
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.
