Evidence for Interstrand Quadruplex Formation in the Dimerization of Human Immunodeficiency Virus 1 Genomic RNA
Retroviruses package two homologous single-stranded RNA genomes within a gag protein-RNA complex. In mature virion particles, the two RNA strands are thought to associate primarily through direct RNA-RNA interactions, although the structural basis for this stable association is unknown. We now repor...
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Veröffentlicht in: | Proceedings of the National Academy of Sciences - PNAS 1993-04, Vol.90 (8), p.3393-3397 |
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Zusammenfassung: | Retroviruses package two homologous single-stranded RNA genomes within a gag protein-RNA complex. In mature virion particles, the two RNA strands are thought to associate primarily through direct RNA-RNA interactions, although the structural basis for this stable association is unknown. We now report that a 127-nucleotide (nt) HIV-1NL4-3RNA fragment (positions 732-858) encompassing the 5' end of the gag gene dimerizes spontaneously under high ionic strength conditions in the absence of any protein cofactor. The HIV-1 RNA dimer is dramatically and specifically stabilized by the monovalent cation potassium. Thermal dissociation of the dimer occurs at 80⚬C in 100 mM K+(5 mM Mg2+) but at significantly lower temperatures in the presence of either smaller or larger monovalent cations (100 mM Li+, 40⚬C; 100 mM Na+, 55⚬C; 100 mM Cs+, 30⚬C). Deletion analyses of the 3' end of the 127-nt fragment reveal that an HIV-1 RNA fragment as short as 94 nt (732-825) can dimerize spontaneously, but a further 9-base deletion of the purine-rich sequence, GGGGGAGAA from positions 817 through 825, eliminates dimerization. These experimental results support a model in which HIV-1 RNA dimerizes by forming an interstrand quadruple helix stabilized by guanine (and/or purine)-base tetrads in analogy to the well-known dimerization of telomeric DNA. We speculate that this structure may also mediate the association of genomic HIV-1 RNA in vivo, revealing how RNA itself can achieve the self-recognition required for subsequent genetic recombination. |
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ISSN: | 0027-8424 1091-6490 |
DOI: | 10.1073/pnas.90.8.3393 |