Termination-Reinitiation of MNV VP2 Synthesis Is Dependent upon an mRNA Sequence with Complementarity to 18S rRNA In FCV, RHDV and influenza B, it has been shown that termination-reinitiation requires a closely conserved primary sequence element (referred to as Motif 1) that is complementary to a region of helix 26 of 18S rRNA [11] [12] 14] ). The position of Motif 1 varies somewhat, with the 59 base 73 nt (RHDV), 63 nt (FCV) or 34 nt (influenza B) upstream of the stop codon of the first ORF. Mutational analysis has revealed that this sequence is essential for the stop-start process [12] [13] [14] [18] [19] . Within the ,43 nt minimal region of the MNV VP1 RNA required for VP2 expression, a stretch of bases with a similar level of complementarity to 18S rRNA is also found (Figure 2a , complementary bases are shown in italics). To investigate whether this region plays a role in termination-reinitiation in VP2 expression, two point mutations were made to disrupt potential mRNA:rRNA pairs ( Figure 2a ). In the first, the A at -31 was mutated to a G (p2luc-MNV GU), creating a presumably slightly weaker putative U-G base pair between the rRNA and mRNA. In the second, the G at -32 was changed to a C (p2luc-MNV CC), which would act to disrupt the interaction between 18S rRNA and mRNA. As can be seen in Figure 2b , the latter mutation greatly reduced expression of the VP2fluc product, supporting the idea that an interaction between the 18S rRNA and the mRNA just upstream of the termination-reinitiation site is required. In the mutant where pairing was predicted to be maintained (p2luc-MNV GU) termination-reinitiation was clearly detectable, although the efficiency was reduced somewhat compared to that of wild-type mRNA.