In vitro processing of the RNA-2-encoded polyprotein of two nepoviruses: tomato black ring virus and grapevine chrome mosaic virus

The nucleotide sequence of RNA-2 of raspberry ringspot nepovirus

“…Cleavage sites for the release of other nepovirus coat proteins from polyprotein precursors are R-A (GCMV; Brault et al, 1989), R-G (GFLV, ArMV; Serghini et al, 1990;Bertioli et al, 1991) and K-A (TBRV; Demangeat et al, 1991). A cleavage site of C-A is unusual in that it has not been reported for any other plant virus or for picornaviruses (Palmenberg, 1987).…”

Immunodetection of the proteins encoded by grapevine chrome mosaic nepovirus RNA2

“…The model derived by Demangeat et al (1991) from in vitro translation/maturation experiments predicts that the polyprotein matures in two steps: (i) cleavage of the C-terminal coat protein leaving a 90K precursor and (ii) cleavage of the 90K precursor to yield two mature products, an N-terminal 44K protein and an internal 46K protein. Antisera were prepared against these two putative non-structural proteins expressed as translational fusion proteins in E. coli.…”

“…As shown in Fig. 1, these two regions were selected to represent most of the putative 44K and 46K maturation products of the polyprotein (Demangeat et al, 1991). Care was taken, when selecting these regions, to allow for some flexibility in the position of the cleavage site between these two products in order to avoid including sequences from one product in the fusion protein corresponding to the other one.…”

“…Indeed, the polyproteins encoded by RNA 1 of different nepoviruses have the characteristic signature sequences of proteins involved in viral RNA replication (Greif et al, 1988;Le Gall et al, 1989;Ritzenthaler et al, 1991). RNA 1 also encodes a proteolytic activity responsible for the maturation of both RNAI-and RNA2-encoded polyproteins (Demangeat et al, , 1991. However, the presence of RNA2 is essential for infection of plants, indicating that this RNA encodes protein(s) involved in the spread of the virus in the plant.…”

“…Recently, Demangeat et al (1991) have used in vitro translation experiments to study the processing of the polyproteins encoded by TBRV and GCMV RNA2. On the basis of their results they have proposed a processing model for both polyproteins.…”