RNA Determinants of Picornavirus Cap-Independent Translation Initiation

Internal ribosome entry was first identified as a translation mechanism used by picornavirus RNAs and has since been shown to be used by other viral and eukaryotic RNAs as well. Cap-independent translation is dependent on complex interactions between eukaryotic factors and picornavirus RNAs in the cytoplasm of the host cell. Determinants for ribosome association lie in the 5′-noncoding region of viral RNAs and consist of several levels of structure including primary sequence, stem-loop structures, and perhaps tertiary folding. Host cell factors involved in this process include some canonical translation factors and additional RNA-binding proteins, of which only a few have been identified. Recent advances in reconstituting translationin vitrohave provided a useful means for deciphering the roles of protein and RNA factors and the steps leading to end-independent protein synthesis.