Exportin 5 is a RanGTP-dependent dsRNA-binding protein that mediates nuclear export of pre-miRNAs
Abstract
microRNAs (miRNAs) are widespread among eukaryotes, and studies in several systems have revealed that miRNAs can regulate expression of specific genes. Primary miRNA transcripts are initially processed to ≈70-nucleotide (nt) stem–loop structures (pre-miRNAs), exported to the cytoplasm, further processed to yield ≈22-nt dsRNAs, and finally incorporated into ribonucleoprotein particles, which are thought to be the active species. Here we study nuclear export of pre-miRNAs and show that the process is saturable and thus carrier-mediated. Export is sensitive to depletion of nuclear RanGTP and, according to this criterion, mediated by a RanGTP-dependent exportin. An unbiased affinity chromatography approach with immobilized pre-miRNAs identified exportin 5 as the pre-miRNA-specific export carrier. We have cloned exportin 5 fromXenopus and demonstrate that antibodies raised against theXenopus receptor specifically block pre-miRNA export from nuclei ofXenopus oocytes. We further show that exportin 5 interacts with double-stranded RNA in a sequence-independent manner.
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Footnotes
↵3 These authors contributed equally to this work.
Article and publication are athttp://www.rnajournal.org/cgi/doi/10.1261/rna.5167604.
- Accepted October 20, 2003.
- Received August 24, 2003.
- Copyright 2004 by RNA Society
