Translating Polyproline: Translation of messenger RNA into protein is carried out by the ribosome, together with a variety of accessory factors, which offer the potential for regulation of this critical step in gene expression (see the Perspective by Buskirk and Green ). Ude et al. (p. 82 , published online 13 December), using bacterial genetics and an in vitro reconstituted translation system, and Doerfel et al. (p. 85 , published online 13 December), using a model assay for peptide bond formation, find that the universally conserved bacterial elongation factor P (EF-P) (which is orthologous to the archaeal and eukaryotic initiation factor 5A) is required for the efficient translation of polyproline-containing polypeptides. Such short polyproline stretches (with runs of two, three, or more proline residues) would otherwise cause ribosomal stalling.