![]() dos Chelysheva, Irina Ignatova, Zoya Arraiano, Cecília M. "Genomic SELEX for Hfq-binding RNAs identifies genomic aptamers predominantly in antisense transcripts". ^ Lorenz C, Gesell T, Zimmermann B, Schoeberl U, Bilusic I, Rajkowitsch L, Waldsich C, von Haeseler A, Schroeder R (2010)."Photorhabdus-nematode symbiosis is dependent on hfq-mediated regulation of secondary metabolites". ^ Tobias NJ, Heinrich AK, Eresmann H, Wright PR, Neubacher N, Backofen R, Bode HB (2016)."Global RNA recognition patterns of post-transcriptional regulators Hfq and CsrA revealed by UV crosslinking in vivo". ^ Holmqvist E, Wright PR, Li L, Bischler T, Barquist L, Reinhardt R, Backofen R, Vogel J (2016)."Loss of Hfq activates the sigmaE-dependent envelope stress response in Salmonella enterica". ^ Figueroa-Bossi N, Lemire S, Maloriol D, Balbontín R, Casadesús J, Bossi L (November 2006)."The RNA chaperone Hfq is essential for the virulence of Salmonella typhimurium". ^ Sittka A, Pfeiffer V, Tedin K, Vogel J (January 2007)."RNase E-dependent processing stabilizes MicX, a Vibrio cholerae sRNA". "Efficient translation of the RpoS sigma factor in Salmonella typhimurium requires host factor I, an RNA-binding protein encoded by the hfq gene". "Hfq modulates the sigmaE-mediated envelope stress response and the sigma32-mediated cytoplasmic stress response in Escherichia coli". ^ Guisbert E, Rhodius VA, Ahuja N, Witkin E, Gross CA (March 2007)."The RNA-binding protein HF-I, known as a host factor for phage Qbeta RNA replication, is essential for rpoS translation in Escherichia coli". ^ Muffler A, Fischer D, Hengge-Aronis R (May 1996)."Characterization of broadly pleiotropic phenotypes caused by an hfq insertion mutation in Escherichia coli K-12". ^ Tsui HC, Leung HC, Winkler ME (July 1994)."Phage-specific and host proteins in the replication of bacteriophage RNA". ^ August JT, Eoyang L, De Fernandez MT, et al.jannaschii ( 2QTX).Īll six structures confirm the hexameric ring-shape of a Hfq protein complex. aureus with bound RNA ( 1KQ2) and without ( 1KQ1), and the Hfq(-like) protein from M. aeruginosa Hfq in a low salt condition ( 1U1S) and a high salt condition ( 1U1T), Hfq from S. Six crystallographic structures of 4 different Hfq proteins have been published so far E. Įlectron microscopy imaging reveals that, in addition to the expected localization of this protein in cytoplasmic regions and in the nucleoid, an important fraction of Hfq is located in close proximity to the membrane. This function on the bacterial ribosome could also account for the pleiotropic effect typical of Hfq deletion strains. Hfq mutants accumulate higher levels of immature small subunits and decreased translation accuracy. Hfq was also found to act on ribosome biogenesis in E. Genomic SELEX has been used to show that Hfq binding RNAs are enriched in the sequence motif 5'-AAYAAYAA-3'. It also acts independently to modulate mRNA decay (directing mRNA transcripts for degradation) and also acts as a repressor of mRNA translation. It interacts with regulatory sRNA and facilitates their antisense interaction with their targets. Hfq mediates its pleiotropic effects through several mechanisms. In Photorhabdus luminescens, a deletion of the hfq gene causes loss of secondary metabolite production. The majority of these binding sites was found in mRNAs and sRNAs. A CLIP-Seq study of Hfq in Salmonella has revealed 640 binding sites across the Salmonella transcriptome. In Salmonella, Hfq deletion mutants are also non motile and exhibit chronic activation of the sigma mediated envelope stress response. In Salmonella typhimurium, Hfq has been shown to be an essential virulence factor as its deletion attenuates the ability of S.typhimurium to invade epithelial cells, secrete virulence factors or survive in cultured macrophages. It also regulates sRNA in Vibrio cholerae, a specific example being MicX sRNA. The Hfq protein is now known to regulate the translation of two major stress transcription factors ( σS (RpoS) and σE (RpoE) ) in Enterobacteria. coli, Hfq mutants show multiple stress response related phenotypes. 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. The Hfq protein (also known as HF-I 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.
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