Structural highlights
Publication Abstract from PubMedThe 5'-untranslated regions of all gammaretroviruses contain a conserved "double-hairpin motif" (Psi(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 ([Psi(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 Ax45 Ax25 A). The global structure was confirmed by cryo-electron tomography (cryo-ET), making [Psi(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, [Psi(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. Structure of a Conserved Retroviral RNA Packaging Element by NMR Spectroscopy and Cryo-Electron Tomography.,Miyazaki Y, Irobalieva RN, Tolbert B, Smalls-Mantey A, Iyalla K, Loeliger K, D'Souza V, Khant H, Schmid MF, Garcia E, Telesnitsky A, Chiu W, Summers MF J Mol Biol. 2010 Oct 8. PMID:20933521[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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