The 3′-Terminal Nucleotide Sequence of Encephalomyocarditis Virus RNA

Poly(A)-containing encephalomyocarditis virus RNA functions as an excellent template for cDNA synthesis in vitro with an RNA-dependent DNA polymerase in the presence of an oligothymidylate primer. Under appropriate conditions, discrete transcripts of increasing chain length were obtained, suitable for sequence analysis. A limited cDNA fragment of 36 nucleotides, primer (dT)10 included, was synthesized when dGTP was omitted from the reaction mixture and its primary structure was elucidated using direct DNA-sequencing methods. The complement corresponds to the 3′ end of encephalomyocarditis RNA. The hexanucleotide (5′-3′)(A-A-U-A-A-A) found in this sequence is also present in all 3′ non-coding regions of poly(A)-containing eukaryotic mRNAs studied until now, in nearly identical positions relative to the poly(A) tail. The possible biological significance of this structural homology is discussed.