cis-acting signals in encapsidation of hantaan virus S-segment viral genomic RNA by its N protein

The nucleocapsid (N) protein encapsidates both viral genomic RNA (vRNA) and the antigenomic RNA (cRNA), but not viral mRNA, Previous work has shown th at the N protein has preference for vRNA, and this suggested the possibilit y of a cis-acting signal that could be used to initiate encapsidation for t he S segment, To map the cis-acting determinants, several deletion RNA deri vatives and synthetic oligoribonucleotides were constructed from the S segm ent of the Hantaan virus (HTNV) VRNA, N protein-RNA interactions were exami ned by UV cross-linking studies, filter-binding assays, and gel electrophor esis mobility shift assays to define the ability of each to bind HTNV N pro tein. The 5' end of the S-segment vRNA was observed to be necessary and suf ficient for the binding reaction. Modeling of the 5' end of the vRNA reveal ed a possible stem-loop structure (SL) with a large single-stranded loop. W e suggest that a specific interaction occurs between the N protein and sequ ences within this region to initiate encapsidation of the vRNAs.