HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1 RNA OUTSIDE THE PRIMARY ENCAPSIDATION AND DIMER LINKAGE REGION AFFECTS RNA DIMER STABILITY IN-VIVO

To characterize the cis-acting determinants that function in RNA dimer formation and maintenance, we examined the stability of RNA dimers is olated from virus particles containing mutations in the encapsidation region of human immunodeficiency virus type 1 (HIV-1). The genomic RNA s of all mutants containing lesions in elements required for in vitro dimerization exhibited thermal stability similar to that of wild-type (WT) HIV-1. These data indicate that the eventual formation of stable dimeric RNA in vivo is not absolutely dependent on the elements that p romote dimer formation in vitro. Surprisingly, mutants that lacked a l arge segment of the middle portion of the genome, outside the likely p rimary dimer linkage region, formed RNA dimers that were measurably mo re stable than WT. In addition, the insertion of one or multiple copie s of a foreign gene, which resulted in a series of vectors that approa ched RNA length similar to that of WT RNA, still exhibited augmented d imer stability. These results suggest that there are regions in the HI V-1 genome outside the primary dimer initiation and dimer linkage regi ons that can negatively affect dimer stability.