Termination-reinitiation in virus systems [9] was first described in the synthesis of the BM2 protein of the orthomyxovirus influenza B virus [10] and subsequently in expression of VP2 of feline calicivirus (FCV) of the genus Vesivirus [11] [12] [13] and VP10 of the calicivirus rabbit haemorrhagic disease virus (RHDV) of the genus Lagovirus [14] . A related phenomenon is also seen in expression of the M2-2 protein [15] [16] of the paramyxovirus respiratory syncytial virus (RSV) and the M2-2 protein [17] of pneumovirus of mice (PVM). In FCV, the stop codon (UGA) of the major capsid stop-start protein VP1 overlaps the start codon of the minor capsid protein VP2 (AUGA) (the stop-start ''window''). Efficient termination-reinitiation depends upon several factors, including the close proximity of the stop and start codons, the transit of ribosomes along the VP1 mRNA up to the stop codon and a stretch of some 70-80 nucleotides (nt) of mRNA upstream of the stop-start window whose primary sequence, rather than the encoded protein, is key. This region of the mRNA, termed the termination upstream ribosomal binding site (TURBS), is needed for the retention of post-termination 40S subunits [11] . A short sequence of the TURBS (termed Motif 1) that is complementary to part of helix 26 of 18S rRNA likely acts to tether the 40S ribosomal subunit to the mRNA post-termination, allowing time for the ribosome to acquire the factors necessary to initiate on the downstream ORF [12, 14, 18] . The TURBS may also act by recruitment of eukaryotic initiation factor 3 (eIF3) or eIF3/40S complexes [13] . Recent studies of termination-reinitiation in the expression of the orthomyxovirus influenza BM2 protein have revealed a requirement for a shorter stretch of mRNA (45 nt) upstream of the stop-start window, but nevertheless, the RNA contains a similar TURBS Motif 1 [19] . From RNA secondary structure probing, it has been proposed that this stretch may be displayed on the apical loop of a stem-loop structure that may form following transit of the ribosome through the region and termination at the upstream ORF stop codon [9, 19] .