5' TERMINI OF PICHINDE ARENAVIRUS S-RNAS AND MESSENGER-RNAS CONTAIN NONTEMPLATED NUCLEOTIDES

Primer extension of Pichinde arenavirus purified virion RNA suggests t hat genomes have at least a single nontemplated base at the 5' end whi ch is a G in all cDNA clones having one such single base. On the other hand, the predominant products of primer extension on total virus-inf ected cell RNA are at positions -1 and -2. The primer extension produc t at position -2 is not represented in virion RNA, and neither of thes e products is proportionally represented in mRNA. mRNA is predominantl y 3 or 4 bases longer than genomes and antigenomes, but primer extensi on products as long as 7 bases were observed. The sequence of nontempl ated bases reported here is unambiguous with respect to the 5'-termina l base and supports the view that there is a sequence preference for a G at the 5' termini of mRNAs. Assessment of our sequence data in the context of the sequences of Tacaribe and lymphocytic choriomeningitis viruses suggests that the mechanism of initiation of arenavirus transc ription is fundamentally different from that of members of the familie s Ortho-myxoviridae and Bunyaviridae.