RNA RECOMBINATION IN TURNIP CRINKLE VIRUS - ITS SOLE IN FORMATION OF CHIMERIC RNAS, MULTIMERS, AND IN 3'-END REPAIR

RNA recombination is well documented for an increasing number of virus es and it is thought to have affected viral evolution and adaptation. However, molecular mechanisms mediating crossover events have been stu died in only a few viral systems due to difficulties such as the low f requency of the event, and the scattered distribution of junction site s. Therefore, the uniquely high recombination frequency and nonrandom crossover site distribution for recombination among turnip crinkle car movirus (TCV) RNAs make TCV an excellent model recombination system. C haracterization of large numbers of junction sites between two species of TCV satellite RNAs and between the TCV genomic RNA and one of the satellite RNAs revealed for the first time the role of specific sequen ces and structures in recombination. Also, recombination was found to play a role in formation of novel chimeric RNAs, multimeric forms of s atellite RNAs as well in 3' end repair of mutated satellite RNAs. A re plicase-driven template-switching model is presented to explain many c ommon features occurring during recombination in TCV infections. (C) 1 996 Academic Press Ltd.