Submitted to: American Society for Virology Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 4/16/1999
Publication Date: N/A
Technical Abstract: Rhopalosiphum padi virus (RhPV) is an insect-infecting virus with a 10 kb ssRNA genome that contains two large open reading frames (ORFs). ORF1 and ORF2 encode the nonstructural and structural polyproteins, respectively. Both ORFs are preceded by noncoding regions of over 500 nt that presumably function as internal ribosome entry sequences (IRESs). To investigate the sequence requirements for translation initiation of ORF2, a series of point and deletion mutations were constructed and transcribed and translated in vitro. Deletions of sequences more than 300 nt upstream of the initiation codon had no effect on translation initiation. Deletions extending upstream from 220 and 120 nt upstream of the initiation codon greatly reduced and abolished translation initiation, respectively. Deletions that included the putative CCU initiation codon failed to initiate protein synthesis. Deletions that started with the second codon and extended downstream showed reduced, but significant levels of translation initiation. Deletions that started with the seventh codon translated normally. These results suggest that the sequences necessary for translation initiation of the RhPV ORF2 include the putative initiation codon and extend about 300 nt upstream. Sequences downstream of the initiation codon were not required.