Gene-protein assignments within the yeast Yarrowia lipolytica dsRNA viral genome

Summary Some strains of the yeast Yarrowia lipolytica possess virus-like particles (VLPs) which encapsidate a double-stranded RNA (dsRNA) genome designated L_y. We report here that these VLPs have two associated polypeptides of molecular weights 83 kd (VL_y-P1) and 77 kd (VL_y-P2). Denatured Ly-dsRNA was used to program a cell-free rabbit reticulocyte translation system, resulting in the appearance of four major products, viz. Ly-P1 (83 kd); L_y-P2 (77 kd); L_y-P3 (74 kd) and L_y-P4 (68 kd). The in vivo viral-associated protein VL_y-P1 co-migrated on SDS-polyacrylamide gels with the in vitro product L_y-P1 and, similarly, VL_y-P2 co-migrated with L_y-P2. Peptide mapping data confirm the identity of the in vivo products (VL_y-P1 and VL_y-P2) and their in vitro counterparts. The conclusion made is that VL_y-P1 and VL_yP2 are almost identical primary translation products of the L_y genome, derived from a single or multiple species of L_y-dsRNA. RNA blot hybridizations using L_1A M₁ and separately, L_2A M₂ probes prepared from appropriate K1 and K2 Saccharomyces cerevisiae killer strains, failed to show any detectable homology to L_y-dsRNA, substantiating the uniqueness of the Ly genome with respect to the K1 and K2 S. cerevisiae dsRNA killer systems.