PROMINENT ROLE OF THE CONSERVED SINGLE-STRANDED INTERDOMAIN LINKER INTHE 5'-UNTRANSLATED REGION OF POLIOVIRUS RNA

Translation of poliovirus RNA is initiated by a mechanism uncommon for eukaryotes, whereby the small ribosomal subunit interacts with intern al segments of the 5'-untranslated region (5UTR). Here, several mutati ons were engineered into the 5UTR segment 425-449. All of them (includ ing a single C-444-->U transition) were found to suppress in vitro tra nslation approximately 10-fold. Two mutant constructs, pPV12-05 (C-444 -->U) and pPV12K (C-444-->U and an AAUU insert between positions 441 a nd 442), yielded infectious revertants when transfected into primary G reen African monkey kidney cells. All the viruses isolated from the pl aques exhibited a reversion at position 444; the template activities o f the revertant RNAs was restored significantly or completely. These r esults demonstrate the importance of the 5UTR segment examined for the initiation of poliovirus RNA translation.