A minimal base-pairing region of a bacterial small RNA SgrS required for translational repression of ptsG mRNA

Authors

  • Kimika Maki,

    1. Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa, Nagoya 464-8602, Japan.
    Search for more papers by this author
    • Kimika Maki and Teppei Morita contributed equally to this work.

  • Teppei Morita,

    1. Faculty of Pharmaceutical Sciences, Suzuka University of Medical Sciences, Suzuka, Mie 513-0816, Japan.
    Search for more papers by this author
    • Kimika Maki and Teppei Morita contributed equally to this work.

  • Hironori Otaka,

    1. Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa, Nagoya 464-8602, Japan.
    Search for more papers by this author
  • Hiroji Aiba

    Corresponding author
    1. Faculty of Pharmaceutical Sciences, Suzuka University of Medical Sciences, Suzuka, Mie 513-0816, Japan.
    Search for more papers by this author

E-mail aiba@suzuka-u.ac.jp; Tel. (+81) 59 340 0573; Fax (+81) 59 368 1271.

Summary

Escherichia coli SgrS is an Hfq-binding small RNA that is induced under glucose-phosphate stress to cause translational repression and RNase E-dependent rapid degradation of ptsG mRNA encoding the major glucose transporter. A 31-nt-long stretch in the 3′ region of SgrS is partially complementary to the translation initiation region of ptsG mRNA. We showed previously that SgrS alone causes translational repression when pre-annealed with ptsG mRNA by a high-temperature treatment in vitro. Here, we studied translational repression of ptsG mRNA in vitro by synthetic RNA oligonucleotides (oligos) to define the SgrS region required for translational repression. We first demonstrate that a 31 nt RNA oligo corresponding to the base-pairing region is sufficient for translational inhibition of ptsG mRNA. Then, we show that RNA oligo can be shortened to 14 nt without losing its effect. Evidence shows that the 14 nt base-pairing region is sufficient to inhibit ptsG translation in the context of full-length SgrS in vivo. We conclude that SgrS 168–181 is a minimal base-pairing region for translational inhibition of ptsG mRNA. Interestingly, the 14 nt oligo efficiently inhibited ptsG translation without the high-temperature pre-treatment, suggesting that remodelling of structured SgrS is an important mechanism by which Hfq promotes the base pairing.

Ancillary