In Vivo and in Vitro Transcription of Small mRNAs Containing a Leader Sequence from Mouse Hepatitis Virus Strain JHM
Mouse hepatitis virus (MHV) genomes are divided into at least seven coding regions. Recently, it has been shown that one or two additional small mRNAs (mRNA8 and 9) are synthesized in DBT cells infected with MHV strains A59, -1 and -SI. It is suggested that the transcription may occur via a leader-priming mechanism whereby a trans-acting leader RNA binds to highly conserved intergenic sequences, UC(U/C)AAAC, on the full-length negative-stranded template to prime transcription of subgenomic mRNAs2,3. mRNA8 is initiated from a perfectly conserved intergenic sequence, UCCAAAC, at 828 nt of the nucleocapsid (N) protein gene of MHV-A59. mRNA9 is initiated from a nearly perfect sequence, UCUAAAU, at 982 nt. However, whether mRNA8 and 9 are synthesized in MHV-infected mice and whether the products from mRNA8 and 9 play a biological role in infected cells remain unknown. In this experiment we studied the course of synthesis of these two small mRNAs in DBT cells and in mouse organs.
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