Coupling of translation initiation and termination does not depend on the mode of initiation

Recently we described a novel phenomenon observed during eukaryotic translation in a cell-free system: the coupling of initiation and termination on different mRNA molecules. Here we show that the phenomenon does not depend on a special mode of initiation. The mRNAs with certain leader sequences known to require different determinants for successful initiation were examined. Even in a case of using the intergenic internal ribosome entry site (IRES) of cricket paralysis virus RNA as the leader sequence, while no initiation factors are required, the effect of coupling is well expressed, including trials in the presence of hippuristanol as an inhibitor of eIF4A. Thus, the effect persists in the absence of scanning and does not depend on initiator tRNA and eIF2. The results suggest that the initiation factors are not involved in the coupling mechanism.