A free leader RNA generated from the genomic RNA of mouse hepatitis virus may participate in the replication of DI RNA, requiring a specific 9-nucleotide sequence for leader sequence switching.
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Highlights sequence requirement for MHV leader switching in animal models; leaves open extension to human coronaviruses or therapeutic targeting.
A system was developed that exploited defective interfering (DI) RNAs of coronavirus to study the role of free leader RNA in RNA replication. A cDNA copy of mouse hepatitis virus DI RNA was placed downstream of the T7 RNA polymerase promoter to generate DI RNAs capable of extremely efficient replication in the presence of a helper virus. We demonstrated that, in the DI RNA-transfected cells, the leader sequence of these DI RNAs was switched to that of the helper virus during one round of replication. This high-frequency leader sequence exchange was not observed if a nine-nucleotide stretch of sequence (UUUAUAAAC) at the junction between the leader and the remaining DI sequence was deleted. This observation suggests that a free leader RNA generated from the genomic RNA of mouse hepatitis virus may participate in the replication of DI RNA.
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Makino et al. (1989) studied this question.
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