Studies on the FCV signal have revealed that the reinitiation process occurs in the standard fashion by the criterion of sensitivity to edeine, but it is distinct in being completely independent of eIF4G or the eIF4F complex [13] . Analysis of the MNV signal here provides further evidence that the process deviates from the standard mechanism. First, like BM2 [19] , there appears to be efficient use of non-AUG codons to reinitiate translation, indicating a relaxed requirement for the full complement of initiation factors, which would include eIF1 and eIF1A, thought to play important roles in locating and correct recognition of the AUG start codon [22] [23] . Secondly, in contrast to what has been observed with FCV and BM2, the MNV signal is more resistant to treatment with edeine. Edeine does not inhibit binding of the eIF2/GTP/Met-tRNAi ternary complex to the 40S ribosomal subunit, nor Met-tRNAi/40S complex scanning, but there is a complete failure of AUG codon recognition, so that scanning continues past all AUG codons, and, probably as a secondary consequence, there is no ribosomal subunit joining [24] [25] . The relative insensitivity of the MNV signal to edeine suggests that recognition of the AUG start codon during reinitiation may not require a scanning ternary complex. It is not clear why the FCV and BM2 signals respond differently to edeine, especially as the organisation of the BM2 signal (with regard to the position of Motif 1 and the primary sequence of the stop-start window) is so similar to that of MNV. Another observation that hints at nonstandard reinitiation mechanisms relates to the the translation pattern seen with the MNV49.8 transcript. In this mRNA, the two termination-reinitiation windows (the natural UAAUG and the fortuitous downstream UGAUG) were mutated to eliminate the stop codon in each case. In translations of this mRNA, where termination occurs 30 amino acids downstream of the authentic site, very little termination-reinitiation product was seen, but an additional product was synthesised whose size is consistent with that of a fusion of the two reporter ORFs (asterisked in Figure 6 ). The origin of this protein is uncertain. It could have arisen through a ribosomal frameshift event, although no obvious conventional frameshift signals are present in the region of overlap between the two ORFs [26] [27] . It could also represent the outcome of a failed attempt to terminate and subsequent resumption of translation by ribosomes on the downstream ORF. Further work will be required to elucidate the nature and origin of this product and how it relates to the mechanism of termination-reinitiation.