Gene products and expression strategy of the M segment of the phlebovirus rift valley fever virus

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genome. 42 GENE PRODUCTSAM) EXPRESSION STRATEGY OF THE M SEGMENT OF THE PHLEBOVIRUS RIFT VALLEY FEVER VIRUS

MARC S. COLLETT, LAURA TQRBORG KAKACH, JOANN A. SUZICH, and TERRI WASMOEN, Molecular Genetics, Inc., 10320 Bren Road East, Minnetonka, MN 55343, U.S.A. We have studied in detail the coding capacity and expression strategy of the Rift Vall.ey fever virus (RVFV) M segment RNA. Using sequence-specific antibody reagents, we have shown that the single large open reading frame (ORF) of the viral-complementary RNA encodes four gene products: the two viral glycoproteins G2. 14kd and Gl, a glycosylated 78kd protein, and a nonglycosylated protein. Using recombinant vaccinia virus technology and a cell-free transcription-translation system, we have further dissected M segment expression. From the cell-free system, the primary translation product of mRNA-like M segment transcripts was a polypeptide encompassing the entire ORF. This precursor polypeptide, which was not observed in RVFV-infected or recombinant RVFV-vaccinia virus-infected cells. was co-translationally processed in vitro in the presence of Further data showed the microsomes to yield the maturFp=ns. 78kd protein was initiated at the first initiation codon Of the ORF and encompassed the entire preglycoprotein and glycoprotein G2 coding sequences. me 14kd protein began from, and required, the second in-phase ATC, and was composed of only preglycoprotein G2 and Gl, each seauences. Concerning the mature qlycoproteins of the five in-phase k?G codons within the pregiycoprotein region are being evaluated for their role in translation initiation for glycoprotein biogenesis. The results to date will be incorporated into a discussion of the mode of gene expression and protein biogenesis by this Phlebovirus M segment. 4~

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