Solution structure of the HIV-1 frameshift inducing stem–loop RNA

AUTOR(ES)

Staple, David W.

FONTE

Oxford University Press

RESUMO

The translation of reverse transcriptase and other essential viral proteins from the HIV-1 Pol mRNA requires a programmed –1 ribosomal frameshift. This frameshift is induced by two highly conserved elements within the HIV-1 mRNA: a slippery sequence comprised of a UUUUUUA heptamer, and a downstream stem–loop structure. We have determined the structure of the HIV-1 frameshift inducing RNA stem–loop, using multidimensional heteronuclear nuclear magnetic resonance (NMR) methods. The 22 nucleotide RNA solution structure [root mean squared deviation (r.m.s.d.) = 1.2 Å] was determined from 475 nuclear Overhauser effect (NOE)-derived distance restrains, 20 residual dipolar couplings and direct detection of hydrogen bonds via scalar couplings. We find that the frameshift inducing stem–loop is an A-form helix capped by a structured ACAA tetraloop. The ACAA tetraloop is stabilized by an equilateral 5′ and 3′ stacking pattern, a sheared A–A pair and a cross-strand hydrogen bond. Unexpectedly, the ACAA tetraloop structure is nearly identical to a known tetraloop fold, previously identified in the RNase III recognition site from Saccharomyces cerevisiae.

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