MUTATIONS IN A SATELLITE RNA OF TURNIP CRINKLE VIRUS RESULT IN ADDITION OF POLY(U) INVIVO

Turnip crinkle virus (TCV) is associated with many subviral RNAs including satellite (sat-) RNAs which require a helper virus for infectivity. When plants were inoculated with TCV and transcripts of TCV sat-RNA C containing deletions of 3 to 8 nucleotides beginning at position 100 and extending toward the 5′ end, some of the sat-RNA isolated from plants migrated more slowly than expected on denaturing polyacrylamide gels. Cleavage of the sat-RNA into two segments by digestion with RNase H following hybridization to an oligonucleotide complementary to internal sat-RNA sequence indicated that the 5′ one-third of the molecule was involved in the abnormal gel migration. Sat-RNAs derived from transcripts with a deletion of bases in position 96-100 were cloned. Sequencing of the cDNAs revealed that the aberrant migration of the sat-RNAs was due to the presence of variable lengths of poly(U) 10 nucleotides downstream from the deletion at a position which already contained five U residues. Deletions extending toward the 3′ end in the same region did not result in poly(U) additions. Mutations in the original five U residues along with the 5′ deletions also did not lead to poly(U) additions. The insertion of poly(U) in TCV sat-RNA C may be a new example of replicase stuttering with the distinction that it only occurs following specific upstream mutations. © 1991.