SUMMARYThe dicistronic genomic RNA 3 of brome mosaic virus (BMV) was used in experiments on site-specific cleavage by RNase H and subsequent religation of large BMV RNA 3 fragments with T4 RNA ligase. BMV RNA 3 was cleaved at the intercistronic poly(A) tract into two fragments: a long (L-BMV 3) Y-terminal fragment (Mr 0.40 x 106) containing the 3a gene, and a short (Sh-BMV 3) fragment (Mr 0.28 x 106) containing the coat protein gene and the Y-terminal tRNA-like tyrosineaccepting structure. Two or three adenylate residues were present at the 5' end of Sh-BMV 3 and one adenylate at the Y end of L-BMV 3. After religation of these RNA fragments BMV RNA 3 was constructed with a deletion including the entire intercistronic poly(A) tract but not the flanking sequences. The religated RNA 3 replicated in wheat plants co-inoculated with BMV RNA 1 and RNA 2. The normal poly(A) tract was restored in progeny BMV RNA 3 during the course of replication.

The TMV RNA molecule can be cleaved at a single site by RNase H directed by chimeric oligo(deoxyribo-ribo)nucleotide with an internucleotide pyrophosphate bond Site specificity; RNA cleavage; RNase H; Oligo(deoxyribo-ribo)nucleotide