Studies on functional interaction between brome mosaic virus replicase proteins during RNA recombination, using combined mutants in vivo and in vitro

Two viral proteins, 1a and 2a, direct replication of brome mosaic bromoviru s (BMV) RNAs as well as they participate in BMV RNA recombination. To study the relationship between replication and recombination, double BMV variant s that carried mutations in la and 2a genes were tested. The observed effec ts revealed that the la helicase and 2a N-terminal or core domains were fun ctionally linked during both processes in vivo. The use of a series of muta nt BMV replicase (RdRp) preparations demonstrated in vitro the participatio n of the 1a and 2a domains in BMV RNA copying and in template switching dur ing minus-strand synthesis. The observed effects support previous observati ons that the characteristics of homologous and nonhomologous recombination can be modified separately by mutations at different sites on BMV replicase proteins. (C) 2001 Academic Press.