Structure of a conserved retroviral RNA packaging element by NMR spectroscopy and cryo-electron tomography.Miyazaki, Y., Irobalieva, R.N., Tolbert, B.S., Smalls-Mantey, A., Iyalla, K., Loeliger, K., D'Souza, V., Khant, H., Schmid, M.F., Garcia, E.L., Telesnitsky, A., Chiu, W., Summers, M.F.
(2010) J.Mol.Biol. 404: 751-772
- PubMed: 20933521
- DOI: 10.1016/j.jmb.2010.09.009
- PubMed Abstract:
The 5'-untranslated regions of all gammaretroviruses contain a conserved "double-hairpin motif" (Ψ(CD)) that is required for genome packaging. Both hairpins (SL-C and SL-D) contain GACG tetraloops that, in isolated RNAs, are capable of forming "kissi ...
The 5'-untranslated regions of all gammaretroviruses contain a conserved "double-hairpin motif" (Ψ(CD)) that is required for genome packaging. Both hairpins (SL-C and SL-D) contain GACG tetraloops that, in isolated RNAs, are capable of forming "kissing" interactions stabilized by two intermolecular G-C base pairs. We have determined the three-dimensional structure of the double hairpin from the Moloney murine leukemia virus ([Ψ(CD)](2), 132 nt, 42.8 kDa) using a (2)H-edited NMR-spectroscopy-based approach. This approach enabled the detection of (1)H-(1)H dipolar interactions that were not observed in previous studies of isolated SL-C and SL-D hairpin RNAs using traditional (1)H-(1)H correlated and (1)H-(13)C-edited NMR methods. The hairpins participate in intermolecular cross-kissing interactions (SL-C to SL-D' and SLC' to SL-D) and stack in an end-to-end manner (SL-C to SL-D and SL-C' to SL-D') that gives rise to an elongated overall shape (ca 95 Å×45 Å×25 Å). The global structure was confirmed by cryo-electron tomography (cryo-ET), making [Ψ(CD)](2) simultaneously the smallest RNA to be structurally characterized to date by cryo-ET and among the largest to be determined by NMR. Our findings suggest that, in addition to promoting dimerization, [Ψ(CD)](2) functions as a scaffold that helps initiate virus assembly by exposing a cluster of conserved UCUG elements for binding to the cognate nucleocapsid domains of assembling viral Gag proteins.
Howard Hughes Medical Institute and Department of Chemistry and Biochemistry, University of Maryland Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250, USA.