RNA, but not protein partners, is directly responsible for translational silencing by a bacterial Hfq-binding small RNA.
SgrS is an Hfq-binding small RNA that is induced under glucose phosphate stress in Escherichia coli. It forms a specific ribo nucleo protein complex with Hfq and RNase E resulting in translational repression and rapid degradation of ptsG mRNA, encoding the glucose transporter. Here, we report translational silencing of ptsG mRNA in a defined in vitro system. We demonstrate that SgrS and Hfq are the minimum components for translational silencing to faithfully reproduce the reaction in cells. We show that ptsG-SgrS base pairing is sufficient to cause translational repression when the ptsG mRNA is forced to base pair with SgrS without the help of Hfq. The extent of translational repression correlates with the extent of duplex formation. We conclude that base pairing itself but not Hfq is directly responsible for translational silencing and the major role of Hfq in gene silencing is to stimulate the base pairing between SgrS and ptsG mRNA. This simple mechanism is in striking contrast to miRNA action in eukaryote in which the RNA is believed to act only as a guide of protein partners.
Maki
Kimika
K
Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa, Nagoya 464-8602, Japan.
Uno
Kanako
K
Morita
Teppei
T
Aiba
Hiroji
H
D020029:Base Pairing; D001483:Base Sequence; D004247:DNA / Q000737:chemistry; D004926:Escherichia coli / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000502:physiology; D015964:Gene Expression Regulation, Bacterial; D020868:Gene Silencing; D035001:Host Factor 1 Protein / Q000378:metabolism; D035683:MicroRNAs / Q000378:metabolism; D008969:Molecular Sequence Data; D010957:Plasmids / Q000378:metabolism; D014176:Protein Biosynthesis; D012313:RNA / Q000737:chemistry*; D012333:RNA, Messenger / Q000378:metabolism
D029968:Escherichia coli Proteins; D035001:Host Factor 1 Protein; D035683:MicroRNAs; D012333:RNA, Messenger; C526013:SgrT protein, E coli; D012313:RNA; D004247:DNA