RNase E action at a distance: degradation of target mRNAs mediated by an Hfq-binding small RNA in bacteria

Model for RNase E action at a distance. (A) Hfq binds to the C-terminal scaffold region of RNase E. When RyhB is induced, it associates with Hfq and therefore RNase E, resulting in a specific ribonucleoprotein complex. (B) The ribonucleoprotein complex acts on the target mRNAs: Hfq facilitates the pairing and RNase E is tethered at the pairing region. The pairing inhibits new ribosome loading, while translating ribosomes protect the downstream RNase E site (shown in red line) from the attack by RNase E. (C) RNase E tethered at the pairing region, but not freestanding RNase E/degradosome, efficiently attacks the RNase E site after the translating ribosomes have passed through. Whether RNase E tethered at the base-pairing region directly attacks the paired RyhB remains to be studied.