The genomic RNA in Ty1 virus-like particles is dimeric

Abstract

The yeast retrotransposon Ty1 resembles retroviruses in a number of important respects but also shows several fundamental differences from them. We now report that, as in retroviruses, the genomic RNA in Ty1 virus-like particles is dimeric. The Ty1 dimers also resemble retroviral dimers in that they are stabilized during the proteolytic maturation of the particle. The stabilization of the dimer suggests that one of the cleavage products of TyA1 possesses nucleic acid chaperone activity.

FIG. 1

Thermal dissociation of Ty1 dimeric RNA. VLPs were isolated after induction of Ty1 expression in strain GRY458 (13), using an established protocol (6). After isolation from the VLP pellets (11) and treatment with DNase, RNA was incubated for 10 min at the indicated temperatures. It was then analyzed by Northern blotting under nondenaturing conditions (11), using a ³²P-labeled riboprobe complementary to nucleotides 241 to 493 of Ty1H3 (GenBank accession no. M18706).

FIG. 2

Thermal dissociation of dimeric RNAs from wild-type and PR⁻ VLPs. RNAs were isolated from VLPs after induction of Ty1 expression in strains GRY458 (WT [wild type]) and GM035 (4, 23). RNAs from the two preparations were incubated in parallel at the indicated temperatures and analyzed as described for Fig. 1.