CRM1-dependent, but not ARE-mediated, nuclear export of IFN-alpha1 mRNA.
While the bulk of cellular mRNA is known to be exported by the TAP pathway, export of specific subsets of cellular mRNAs may rely on chromosome region maintenance 1 (CRM1). One line of evidence supporting this hypothesis comes from the study of mRNAs of certain early response genes (ERGs) containing the adenylate uridylate-rich element (ARE) in their 3' untranslated regions (3' UTRs). It was reported that HuR-mediated nuclear export of these mRNAs was CRM1-dependent under certain stress conditions. To further examine potential CRM1 pathways for other cellular mRNAs under stress conditions, the nuclear export of human interferon-alpha1 (IFN-alpha1) mRNA, an ERG mRNA induced upon viral infection, was studied. Overproduction of human immunodeficiency virus type 1 Rev protein reduced the expression level of the co-transfected IFN-alpha1 gene. This inhibitory effect, resulting from nuclear retention of IFN-alpha1 mRNA, was reversed when rev had a point mutation that made its nuclear export signal unable to associate with CRM1. Leptomycin B sensitivity experiments revealed that the cytoplasmic expression of IFN-alpha1 mRNA was arrested upon inhibition of CRM1. This finding was further supported by overexpression of DeltaCAN, a defective form of the nucleoporin Nup214/CAN that inhibits CRM1 in a dominant-negative manner, which resulted in the effective inhibition of IFN-alpha1 gene expression. Subsequent RNA fluorescence in situ hybridisation and immunocytochemistry demonstrated that the IFN-alpha1 mRNA was colocalised with CRM1, but not with TAP, in the nucleus. These results therefore imply that the nuclear export of IFN-alpha1 mRNA is mediated by CRM1. However, truncation of the 3' UTR did not negatively affect the nuclear export of IFN-alpha1 mRNA that lacked the ARE, unexpectedly indicating that this CRM1-dependent mRNA export may not be mediated via the ARE.
Kimura
Tominori
T
Department of Microbiology, Kansai Medical University, Moriguchi, Osaka 570-8506, Japan.
Hashimoto
Iwao
I
Nagase
Takahiro
T
Fujisawa
Jun-Ichi
J
D020413:3' Untranslated Regions / Q000235:genetics / Q000378:metabolism; D018528:ATP-Binding Cassette Transporters; D021581:Active Transport, Cell Nucleus / Q000187:drug effects; D000225:Adenine; D002467:Cell Nucleus / Q000235:genetics / Q000378:metabolism*; D003593:Cytoplasm / Q000235:genetics / Q000378:metabolism; D005231:Fatty Acids, Unsaturated / Q000494:pharmacology; D015694:Gene Products, rev / Q000235:genetics / Q000378:metabolism; D006367:HeLa Cells; D015395:Histocompatibility Antigens Class I / Q000378:metabolism; D006801:Humans; D016898:Interferon-alpha / Q000235:genetics*; D028884:Karyopherins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D009154:Mutation; D028861:Nuclear Pore Complex Proteins / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D034443:RNA Transport / Q000187:drug effects; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism*; D018160:Receptors, Cytoplasmic and Nuclear / Q000037:antagonists & inhibitors / Q000378:metabolism*; D038621:Regulatory Sequences, Ribonucleic Acid / Q000235:genetics*; D014162:Transfection; D014529:Uridine; D000097606:Exportin 1 Protein
D020413:3' Untranslated Regions; D018528:ATP-Binding Cassette Transporters; D000225:Adenine; D005231:Fatty Acids, Unsaturated; D015694:Gene Products, rev; D015395:Histocompatibility Antigens Class I; D016898:Interferon-alpha; D028884:Karyopherins; D028861:Nuclear Pore Complex Proteins; D012333:RNA, Messenger; D018160:Receptors, Cytoplasmic and Nuclear; D038621:Regulatory Sequences, Ribonucleic Acid; D014529:Uridine; D000097606:Exportin 1 Protein; C085914:NUP214 protein, human; C477327:transporter associated with antigen processing (TAP); C038753:leptomycin B