We have analyzed the replication of deletion mutants of defective interfering (DI) RNAs derived from the coronavirus mouse hepatitis virus (MHV)-A59 in the presence of MHV-A59. Using two parental DI RNAs, MIDI and MIDIฮ”H, a twin set of deletion mutants was generated with progressively shorter stretches of 5โ€ฒ sequence colinear with the genomic RNA. All deletion mutants contained in-frame ORFs. We show that in transfected cells and after one passage the DI RNAs were detectable and that their accumulation was positively correlated with the length of 5โ€ฒ sequence they contained. However, accumulation of two twin mutants, ฮ”2, in which sequences from nucleotide position 467 were fused to those from position 801, was undetectable. In passage 4 cells, but not in transfected or in passage 1 cells, recombination with genomic RNA led to the appearance of the parental DI RNAs. The accumulation of these parental RNAs was inversely correlated with the length of 5โ€ฒ sequence on the deletion mutants and was highest in the ฮ”2 samples. In sharp contrast to the data reported for MHV-JHM-derived DI RNAs, we show that MHV-A59-derived mutant RNAs do not require an internal sequence domain for replication. The data suggest that coronavirus replication involves an RNA superstructure at the 5โ€ฒ end of the genome or one comprising both ends of the genomic RNA. We also conclude from the recombination data that in-frame mutants with impaired replication signals are more fit than out-frame mutants with intact replication signals, ยฉ 1995 Academic Press, Inc.
year โฐ 1996
issn ๐Ÿ—„ 00426822
volume 216
number 1
page 174-183
citedbycount 26