EVIDENCE FOR NEW TRANSCRIPTIONAL UNITS ENCODED AT THE 3' END OF THE MOUSE HEPATITIS-VIRUS GENOME

Prior studies have demonstrated that the mouse hepatitis virus (MHV) genome is divided into at least seven coding regions each transcribed into a distinct mRNA. The majority of these mRNAs are synthesized from a highly conserved intergenic start site (UCU/CAAAC), contain a 65-72 nt leader RNA at their 5′ end and form a 3′ co-terminal nested set. In this study, we have used radiolabeling experiments to demonstrate the presence of a small ∼900 nt mRNA and its corresponding RF RNA in MHV-infected cells. Surprisingly, PCR amplification and sequence analysis revealed the presence of not one, but two small leader-containing RNAs that initiate from highly conserved intergenic start sites (UCCAAAC and UCUAAAU) which are located within the 3′-most nucleocapsid gene sequence. These studies provide evidence suggesting that one or two additional small mRNAs are encoded from the 3′ end of the MHV genome. © 1993 Academic Press.