Identification of virus-coded nonstructural polypeptides in bunyavirus-infected cells

Abstract

Analyses of bunyavirus-infected cell extracts identified at least two virus-induced nonstructural polypeptides. With snowshoe hare (SSH), La Crosse (LAC), and six SSH-LAC reassortant viruses, it was shown that one of these nonstructural polypeptides (NSs, approximate molecular weight, 7.4 X 10(3)) is coded by the SSH small (S)-size viral RNA species. This nonstructural polypeptide was not detected (at least in the same relative abundancies) in LAC virus-infected cells or in cells infected with reassortants having LAC S RNA. For SSH virus, tryptic peptide analyses of either [3H]leucine- or [3H]arginine-labeled NSs indicated that it contains unique sequences not present in the SSH nucleocapsid (N) polypeptide (also coded by the S RNA; J. R. Gentsch and D. H. L. Bishop, J. Virol. 28:417-419, 1978). Analyses of SSH virus-infected cell extracts and extracts of cells infected with SSH-LAC reassortants having SSH medium (M)-size RNA species indicated that a nonstructural polypeptide (NSM; approximate molecular weight, 12 X 10(3)) is coded by the SSH M RNA species. In extracts of LAC virus-infected cells (or cells infected with SSH-LAC reassortants having LAC M RNA), a polypeptide with an electrophoretic mobility slightly faster than that of the SSH NSM polypeptide was observed (approximate molecular weight, 11 X 10(3)); it has been designated LAC NSM. The relationships of the NSM polypeptides to the other M RNA-coded polypeptides (G1 and G2; J. R. Gentsch and D. H. L. Bishop, J. Virol. 30;767-770, 1979) have not been determined. Two additional polypeptides present in both LAC- and SSH-infected cell extracts also appear to be virus induced (one with an approximate molecular weight of 10 X 10(3), p10; the other with an approximate molecular weight of 18 X 10(3), p18). Whether these polypeptides are virus coded has not been determined.