rev
Domain
The RNA-binding motif binds to the RRE, a 240 bp stem-and-loop structure present in incompletely spliced viral pre-mRNAs. This region also contains the NLS which mediates nuclear localization via KPNB1 binding and, when the N-terminal sequence is present, nucleolar targeting. These overlapping functions prevent Rev bound to RRE from undesirable return to the nucleus. When Rev binds the RRE, the NLS becomes masked while the NES remains accessible. The leucine-rich NES mediates binding to human XPO1.
Function
Escorts unspliced or incompletely spliced viral pre-mRNAs (late transcripts) out of the nucleus of infected cells. These pre-mRNAs carry a recognition sequence called Rev responsive element (RRE) located in the env gene, that is not present in fully spliced viral mRNAs (early transcripts). This function is essential since most viral proteins are translated from unspliced or partially spliced pre-mRNAs which cannot exit the nucleus by the pathway used by fully processed cellular mRNAs. Rev itself is translated from a fully spliced mRNA that readily exits the nucleus. Rev's nuclear localization signal (NLS) binds directly to KPNB1/Importin beta-1 without previous binding to KPNA1/Importin alpha-1. KPNB1 binds to the GDP bound form of RAN (Ran-GDP) and targets Rev to the nucleus. In the nucleus, the conversion from Ran-GDP to Ran-GTP dissociates Rev from KPNB1 and allows Rev's binding to the RRE in viral pre-mRNAs. Rev multimerization on the RRE via cooperative assembly exposes its nuclear export signal (NES) to the surface. Rev can then form a complex with XPO1/CRM1 and Ran-GTP, leading to nuclear export of the complex. Conversion from Ran-GTP to Ran-GDP mediates dissociation of the Rev/RRE/XPO1/RAN complex, so that Rev can return to the nucleus for a subsequent round of export. Beside KPNB1, also seems to interact with TNPO1/Transportin-1, RANBP5/IPO5 and IPO7/RANBP7 for nuclear import. The nucleoporin-like HRB/RIP is an essential cofactor that probably indirectly interacts with Rev to release HIV RNAs from the perinuclear region to the cytoplasm.
Post-translational modifications
Asymmetrically arginine dimethylated at one site by host PRMT6. Methylation impairs the RNA-binding activity and export of viral RNA from the nucleus to the cytoplasm.
Phosphorylated by protein kinase CK2. Presence of, and maybe binding to the N-terminus of the regulatory beta subunit of CK2 is necessary for CK2-mediated Rev's phosphorylation.
Sequence Similarities
Belongs to the HIV-1 REV protein family.
Cellular localization
- Host nucleus
- Host nucleolus
- Host cytoplasm
- The presence of both nuclear import and nuclear export signals leads to continuous shuttling between the nucleus and cytoplasm.
Alternative names
Protein Rev, ART/TRS, Anti-repression transactivator, Regulator of expression of viral proteins, rev