THE 5' UNTRANSLATED REGION OF PVY RNA, EVEN LOCATED IN AN INTERNAL POSITION, ENABLES INITIATION OF TRANSLATION

Potato virus Y (PVY) is the type member of the potyvirus group. Potyvi ruses, like picorna-, como-, and nepoviruses, belong to the picornavir us-like supergroup. All these viral RNAs have a VPg at their 5' end, a nd for four picornaviruses and one comovirus internal initiation of tr anslation has been reported. To know if such a translational mechanism holds true for potyviral RNAs, the 5' nontranslated region (NTR) of P VY RNA was placed in an internal position, either by adding 91 bases u pstream of the PVY 5'NTR or by inserting the PVY 5'NTR into an interci stronic region. The addition of extra bases stimulates translation in a rabbit reticulocyte lysate, and the presence of the PVY 5'NTR in the intercistronic region allows the synthesis of the second cistron. The se findings strongly suggest that PVY RNA initiates translation by an internal ribosome-binding mechanism. Furthermore, the use of antisense oligodeoxynucleotides indicates that the entire 5'NTR seems to be inv olved in such a mechanism.