Viruses have evolved a number of translational control mechanisms to regulate 
the levels of expression of viral proteins on polycistronic mRNAs, including 
programmed ribosomal frameshifting and stop codon readthrough. More recently, 
another unusual mechanism has been described, that of termination-dependent 
re-initiation (also known as stop-start). Here, the AUG start codon of a 3' ORF 
(open reading frame) is proximal to the termination codon of a uORF (upstream 
ORF), and expression of the two ORFs is coupled. For example, segment 7 mRNA of 
influenza B is bicistronic, and the stop codon of the M1 ORF and the start codon 
of the BM2 ORF overlap in the pentanucleotide UAAUG (stop codon of M1 is shown 
in boldface and start codon of BM2 is underlined). This short review aims to 
provide some insights into how this translational coupling process is regulated 
within different viral systems and to highlight some of the differences in the 
mechanism of re-initiation on prokaryotic, eukaryotic and viral mRNAs.