Not Lost In Translation

Science's STKE  04 Sep 2007:
Vol. 2007, Issue 402, pp. tw322
DOI: 10.1126/stke.4022007tw322

Protein synthesis by ribosomes normally requires that the messenger RNA (mRNA) template be capped at its 5′ end with a modified nucleotide. Starved yeast can undergo a developmental switch to an invasive phenotype, during which most mRNAs are decapped, which prevents their translation by ribosomes. The genes responsible for the switch must therefore be translated in a cap-independent manner. Gilbert et al. now show that invasive growth-specific genes have internal ribosome entry sites (IRESs) in the unusually long 5′ untranslated regions of their mRNAs that allow their translation. Unlike viral IRESs, these cellular IRESs seem to consist of an unstructured sequence of adenosines that recruits the poly-A binding protein, a configuration that can substitute for the 5′ cap.

W. V. Gilbert, K. Zhou, T. K. Butler, J. A. Doudna, Cap-independent translation is required for starvation-induced differentiation in yeast. Science 317, 1224-1227 (2007). [Abstract] [Full Text]