Download MendeleySolution Structure and Thermodynamic Investigation of the HIV-1 Frameshift Inducing Element.
Staple, D.W., Butcher, S.E.(2005) J Mol Biol 349: 1011-1023
- PubMed: 15927637
- DOI: https://doi.org/10.1016/j.jmb.2005.03.038
- Primary Citation of Related Structures:
1Z2J - PubMed Abstract:
Expression of the HIV reverse transcriptase and other essential viral enzymes requires a -1 translational frameshift. The frameshift event is induced by two highly conserved RNA elements within the HIV-1 mRNA: a UUUUUUA heptamer known as the slippery sequence, and a downstream RNA structure. Here, we report structural and thermodynamic evidence that the HIV-1 frameshift site RNA forms a stem-loop and lower helix separated by a three-purine bulge. We have determined the structure of the 45 nucleotide frameshift site RNA using multidimensional heteronuclear nuclear magnetic resonance (NMR) methods. The upper helix is highly thermostable (T(m)>90 degrees C), forming 11 Watson-Crick base-pairs capped by a stable ACAA tetraloop. The eight base-pair lower helix was found to be only moderately stable (T(m)=47 degrees C). A three-purine bulge separates the highly stable upper helix from the lower helix. Base stacking in the bulge forms a wedge, introducing a 60 degrees bend between the helices. Interestingly, this bend is similar to those seen in a number of frameshift inducing pseudoknots for which structures have been solved. The lower helix must denature to allow the ribosome access to the slippery site, but likely functions as a positioning element that enhances frameshift efficiency.
Organizational Affiliation:
Department of Biochemistry, University of Wisconsin-Madison, WI 53706, USA.
