The ABC-F protein Uup, Rescues Stalled Ribosomal Termination Complexes to Modulate DNA Maintenance

The cytosolic ATP-binding cassette F (ABC-F) family modulates ribosomal activity in eukaryotes and prokaryotes. Although they all bind to the E site of the ribosome, some bacterial ABC-Fs confer resistance to ribosome-targeting antibiotics, while housekeeping members have poorly defined roles. Interestingly, in Escherichia coli, which possesses four ABC-F (EttA, Uup, YbiT and YheS), Uup has been rather implicated in DNA recombination. Using an unbiased approach, we reconcile this apparent discrepancy by showing that Uup's involvement in DNA recombination is indirect and is dictated by Uup-mediated regulation of the last steps of translation that rescues problematic translation of genes involved in DNA maintenance such as ssb and dnaX. Accordingly, the elongated cell phenotype observed in uup deletion background is reverted by expressing a ssb variant that no longer depends on Uup. Unlike its paralog EttA, which helps ribosomes in translating proteins with repeats of negatively charged residues in the N-terminal 30 amino acids, Uup instead facilitates the rescue of stalled translation termination events that, in its absence, are handled by the tmRNA pathway.