The multimerization state of retroviral RNA is modulated by ammonium ions and affects HIV-1 full-length cDNA synthesisin vitro

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Abstract
Genomic human immunodeficiency virus type 1 (HIV-1) RNA fragments containing the dimer linkage structure (DLS) can be dimerized and multimerized in the presence of NH 4 + and in the absence of any other cation and any viral or cellular protein. This effect strongly supports the notion that dimerization and multimerization of genomic RNA occurs via purinequartet formation in quadruple helical RNA structures. The efficiency of RNA dimerization and multimerization in the presence of ammonium ions is about 400 fold increased as compared to alkali metal ions such as potassium. Dimerized retroviral RNA representing a pseudodiploid genome could account for genetic recombination within the virion and during reverse transcription. Application of a novel South-Northern- Blotting procedure with biotinylated RNA and digoxigenin-labelled cDNA in vitro reveals that efficient human- and bovine tRNA Lys3 primed full-length cDNAsynthesis only takes place with a predominantly monomerized RNA template. Dimerization and multimerization of the RNA significantly reduces fulllength cDNA-synthesis. This suggests that monomerization of the dimerized RNA, effected by deionization in vitro , is essential for efficient retroviral reverse transcription in vivo .