Nuclear Export of MicroRNA Precursors

MicroRNAs (miRNAs), which function as regulators of gene expression in eukaryotes, are processed from larger transcripts by sequential action of nuclear and cytoplasmic ribonuclease III–like endonucleases. We show that Exportin-5 (Exp5) mediates efficient nuclear export of short miRNA precursors (pre-miRNAs) and that its depletion by RNA interference results in reduced miRNA levels. Exp5 binds correctly processed pre-miRNAs directly and specifically, in a Ran guanosine triphosphate–dependent manner, but interacts only weakly with extended pre-miRNAs that yield incorrect miRNAs when processed by Dicer in vitro. Thus, Exp5 is key to miRNA biogenesis and may help coordinate nuclear and cytoplasmic processing steps.

[1]  V. Ambros,et al.  The C. elegans heterochronic gene lin-4 encodes small RNAs with antisense complementarity to lin-14 , 1993, Cell.

[2]  B. Cullen,et al.  Sequence requirements for micro RNA processing and function in human cells. , 2003, RNA.

[3]  U. Kutay,et al.  Nucleocytoplasmic transport: taking an inventory , 2003, Cellular and Molecular Life Sciences CMLS.

[4]  V. Ambros,et al.  An Extensive Class of Small RNAs in Caenorhabditis elegans , 2001, Science.

[5]  F. Slack,et al.  Control of developmental timing by small temporal RNAs: a paradigm for RNA‐mediated regulation of gene expression , 2002, BioEssays : news and reviews in molecular, cellular and developmental biology.

[6]  A. Pasquinelli,et al.  A Cellular Function for the RNA-Interference Enzyme Dicer in the Maturation of the let-7 Small Temporal RNA , 2001, Science.

[7]  D. Dykxhoorn,et al.  Killing the messenger: short RNAs that silence gene expression , 2003, Nature Reviews Molecular Cell Biology.

[8]  E. Moss,et al.  MicroRNAs: Something New Under the Sun , 2002, Current Biology.

[9]  C. Grimm,et al.  In vivo selection of RNAs that localize in the nucleus , 1997, The EMBO journal.

[10]  M. Terns,et al.  3'-end-dependent formation of U6 small nuclear ribonucleoprotein particles in Xenopus laevis oocyte nuclei , 1992, Molecular and cellular biology.

[11]  G. Hannon,et al.  C . elegans involved in developmental timing in Dicer functions in RNA interference and in synthesis of small RNA , 2001 .

[12]  U. Kutay,et al.  The asymmetric distribution of the constituents of the Ran system is essential for transport into and out of the nucleus , 1997, The EMBO journal.

[13]  M. Mann,et al.  miRNPs: a novel class of ribonucleoproteins containing numerous microRNAs. , 2002, Genes & development.

[14]  U. Kutay,et al.  Exportin‐5‐mediated nuclear export of eukaryotic elongation factor 1A and tRNA , 2002, The EMBO journal.

[15]  T. Berardini,et al.  HASTY, the Arabidopsis ortholog of exportin 5/MSN5, regulates phase change and morphogenesis , 2003, Development.

[16]  Edouard Bertrand,et al.  Exportin-5 Mediates Nuclear Export of Minihelix-containing RNAs* , 2003, The Journal of Biological Chemistry.

[17]  Blanche Schwappach,et al.  Exp5 exports eEF1A via tRNA from nuclei and synergizes with other transport pathways to confine translation to the cytoplasm , 2002, The EMBO journal.

[18]  Michael Q. Zhang,et al.  The Argonaute family: tentacles that reach into RNAi, developmental control, stem cell maintenance, and tumorigenesis. , 2002, Genes & development.

[19]  W. Filipowicz,et al.  Human Dicer preferentially cleaves dsRNAs at their termini without a requirement for ATP , 2002, The EMBO journal.

[20]  L. Lim,et al.  An Abundant Class of Tiny RNAs with Probable Regulatory Roles in Caenorhabditis elegans , 2001, Science.

[21]  I. Macara,et al.  Exportin-5, a novel karyopherin, mediates nuclear export of double-stranded RNA binding proteins , 2002, The Journal of cell biology.

[22]  A. Pasquinelli,et al.  Control of developmental timing by micrornas and their targets. , 2002, Annual review of cell and developmental biology.

[23]  C. Kidner,et al.  Macro effects of microRNAs in plants. , 2003, Trends in genetics : TIG.

[24]  T. Tuschl,et al.  Identification of Novel Genes Coding for Small Expressed RNAs , 2001, Science.

[25]  V. Ambros,et al.  Role of MicroRNAs in Plant and Animal Development , 2003, Science.

[26]  V. Kim,et al.  MicroRNA maturation: stepwise processing and subcellular localization , 2002, The EMBO journal.

[27]  V. Kim,et al.  The nuclear RNase III Drosha initiates microRNA processing , 2003, Nature.