exportin-5 (Exp5, Ran-binding protein 21, XPO5, KIAA1291, RANBP21)
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Function
- mediates the nuclear export of proteins bearing a double-stranded RNA binding domain & double-stranded RNAs (cargo)
- XPO5 in the nucleus binds cooperatively to RNA & to the GTPase Ran in its active GTP-bound form (trimeric complex)
- proteins containing double-stranded RNA binding domains can associate with this trimeric complex through RNA
- docking of this complex to the nuclear pore complex is mediated through binding to nucleoporins
- upon transit of a nuclear export complex into cytoplasm, hydrolysis of Ran-GTP to Ran-GDP (induced by RANBP1 & RANGAP1, respectively) cause disassembly of the complex & release of the cargo from the export receptor
- XPO5 then returns to the nuclear compartment by diffusion through the nuclear pore complex, to mediate another round of transpor
- directionality of nuclear export is thought to be conferred by an asymmetric distribution of the GTP- & GDP-bound forms of Ran between cytoplasm & nucleus
- overexpression may in some circumstances enhance RNA-mediated gene silencing (RNAi).
- mediates nuclear export of micro-RNA precursors, which form short hairpins
- also mediates the nuclear export of synthetic short hairpin RNAs used for RNA interference
- mediates nuclear export of deacylated & aminoacylated tRNAs
- recognizes dsRNAs that lack a 5' overhang (sequence- independent), have only a short 3' overhang, & that have a double-stranded length of at least 15 base-pairs (Ran-GTP-dependent)
- component of nuclear export receptor complexes
- interacts with EEF1A1, ILF3, NUP153, NUP214 & ZNF346
- interacts with Ran & cargo proteins (GTP-dependent)
Structure
- belongs to the exportin family
Compartment
Alternative splicing
named isoforms=2
Expression
- expressed in heart, brain, placenta, lung, skeletal muscle, kidney, pancreas
Pathology
- mediates the nuclear export of adenovirus VA1 dsRNA