Translation of the second gene of peanut clump virus RNA 2 occurs by leaky scanning in vitro.

The two 5'-proximal open reading frames of peanut clump virus RNA 2, which encode the coat protein of 23 kDa and a protein of 39 kDa (P39), are both translated in vitro from genomic RNA 2. We have studied the translational strategy involved in the initiation at the second AUG of RNA 2, which is the initiation codon of P39. Mutation experiments with synthetic transcripts corresponding to the 5'-half of RNA 2 ruled out mechanisms of P39 translation initiation involving termination-reinitiation and internal ribosomes entry. The results were consistent, however, with a leaky scanning mechanism for P39 initiation, in which about one-third of the ribosomes fail to initiate translation of coat protein and scan along the template to initiate translation at the AUG of the P39 gene, more than 1000 residues in from the 5'-terminus of the RNA 2.