HARC Center: HIV Accessory and Regulatory Complexes

University Of California, San Francisco, San Francisco CA

Investigators

Linked publications, trials & patents

Abstract

Rev functions primarily to export unspliced viral RNAs to the cytoplasm by interacting with the Crmi nuclear export receptor, a process that requires Rev assembly into an oligomenc complex on the RRE [81, 82]. The arrangement of the oligomer is interesting in that individual subunits of Rev bind cooperatively to different sites on the RNA using distinct faces of its helical ARM (arginine-rich motif). An important aim is to define how the protein-protein interfaces direct the placement of binding sites on the RNA scaffold [83]. Aside from the NMR structure of a Rev ARM peptide bound to the high affinity RRE IIB hairpin [84], little is known about how Rev recognizes the RRE and how the higher order complex is assembled. We recently took an important step in this direction by solving the 2.5-A-resolufion crystal structure of dimeric Rev. Dimers were arranged in higher-order oligomers in the crystal [5] via a second interface identical to that observed in a Rev-Fab complex [85]. These structures supported our jellyfish model in which six Rev subunits bound to the 250nt RRE form a bridge to Crml/RanGTP nuclear export complexes by interactions with Rev NES (nuclear export sequence) peptides. Going forward, we will build on our substantial progress in visualizing the entire Rev/RRE/export complex. Rev bound to the large, full-length RRE forms discrete particles by EM [83], and we have established conditions to purify complete, well-defined export complexes with Crml/RanGTP that suggest one receptor binds to each Rev-RRE oligomer. The Rev-RRE cargo appears located on the outside of the Crmi toroid, consistent with how the NES binds to the complex [86]. We are poised to discover the full molecular architecture of the Rev/RRE RNP and export complexes. In addition, there is evidence that Rev also may function after RNA export and may influence translation or RNA packaging [87-90]. Our characterization of several provocative Rev partners identified in our proteomics work as candidates for post-export activities in the cytoplasm has the potential to expand current models of Rev function.