The precise mechanism of termination-reinitiation is not known, but the sensitivity of FCV VP2 protein expression to the translation initiation inhibitor edeine suggests that the reinitiation process bears at least some similarity to standard initiation at AUG codons [13] . To ascertain whether edeine sensitivity is a general feature of termination-reinitiation, we analysed the effect of the peptide on the activity of the MNV and BM2 signals (with FCV as a control) using translation time-courses (Figure 7 ). Reactions were programmed with the relevant mRNA and at various times an aliquot was removed, edeine added (to 5 mM) and the aliquot reincubated such that the total time of translation was 60 minutes. To determine the time of first appearance of the termination and reinitiation products, identical reactions were also performed in which the elongation inhibitor cycloheximide replaced edeine. In the edeine experiments, it was evident that for FCV and BM2, only a trace of ''stop-start'' product was synthesised at the early time points. In these experiments, the vast majority of ribosomes did not reach the stop-start window until at least 7.5 minutes had passed (as shown in the cycloheximide time course experiments [data not shown; see legend to Figure 7 ]), thus the trace of VP2fluc seen likely corresponds to the product of infrequent internal initiation at the VP2fluc AUG or is derived from those few ribosomes that had reached the stop-start window prior to edeine addition. At later time points, however, the termination-reinitiation product steadily accumulated, with the ratio of the upstream and downstream ORFs stabilising after 30 minutes (at a reinitiation frequency of ,4%). Thus for the FCV and BM2 signals, when edeine is present prior to arrival of ribosomes at the stop-start signal, it greatly inhibits termination-reinitiation, but has little effect on translation post-reinitiation. Unexpectedly, the MNV signal responded differently, with the termination-reinitiation product being more evident at early times post-edeine addition (in comparison to FCV and BM2). At these early time points, few ribosomes would have reached the stop-start window prior to edeine addition, thus the MNV signal shows increased resistance to the effects of edeine. Examination of the kinetics of synthesis of the two ORFs (Figure 7d ) reveals that in all cases, the frequency of termination-reinitiation at early time points was higher than that seen at the steady state. This is indicative of a titration effect; early in the time course, when fewer ribosomes have loaded onto the mRNA (due to the earlier addition of edeine), the greater frequency of reinitiation may reflect the increased relative abundance of a necessary factor. The molecular basis of the resistance to edeine seen with the MNV signal is difficult to explain. It may be that recognition of the stop-start motif is indeed blocked by edeine but somehow, a proportion of initiation complexes still recognise the AUG present in the second pentanucleotide motif (UGAUG; see above) on the mRNA.