Molecular cloning of Lassa virus RNA: nucleotide sequence and expression of the nucleocapsid protein gene.

Lassa virus RNA isolated from purified virus particles was polyadenylated and reverse transcripts were cloned into the PstI site of plasmid pUC9. Clones containing sequences of the smaller (S) segment of the Lassa virus genome were identified by hybridization with purified S RNA. They were characterized by their ability to hybridize with fragments of 3'-labeled Lassa virus S RNA and with each other, and by restriction mapping. The largest insert was 1830 bp long and began with the 3'-terminal 19-base sequence characteristic of all arenavirus S RNAs so far analyzed. The virus complementary strand contained a single large open reading frame, beginning at the ATG nearest its 5' end (nucleotides 103-5) and terminating with a TGA triplet at position 1813-15, that encodes a protein of 570 amino acids. A recombinant was constructed which expressed the gene as a fusion protein in Escherichia coli. The product was a 60-kDa polypeptide which reacted with monoclonal antibodies specific for the nucleocapsid protein. Comparison of the predicted amino acid sequence with the corresponding sequences deduced from the nucleotide sequences of the other arenavirus S RNAs, lymphocytic choriomeningitis (LCM) and Pichinde, reveals a considerable degree of similarity between Old and New World arenaviruses.