Novel cis-active structures in the coding region mediate CRM1-dependent nuclear export of IFN-α 1 mRNA.
We recently reported the chromosome region maintenance 1 (CRM1)-dependent nuclear export of intron-less human interferon-α1 (IFN-α1) mRNA, which encodes a main effecter of host innate immunity. We show that the coding region of IFN-α1 mRNA forms novel secondary structures that are responsible for the CRM1-dependent export of the transcript. Deletion-mutagenesis, in vivo export assays, and computer analyses of the folding potentials of export-competent fragments revealed the presence of a domain, termed the conserved secondary structure (CSS), comprising two adjacent putative stable stem-loop structures (nt 208-452). Internal deletion-mutagenesis and constitutive export assays of each stem-loop structure demonstrated that subregions 308-322 and 352-434 act as a core element by conferring the export function on the CSS. Leptomycin B (LMB) inhibition of the CRM1 pathway decreased the export of core element RNA, implying that the principal site of CRM1 action for exporting IFN-α1 mRNA resides within the core element. An RNPS1 (RNA-binding protein S1, serine-rich domain) cDNA was isolated by yeast three-hybrid screening, using bait containing two CSS regions. We showed that RNPS1 might recognize IFN-α1 mRNP that includes CRM1. The data demonstrate that interaction between RNA structures in the coding region and CRM1 affects the nucleocytoplasmic translocation of IFN-α1 mRNA.
Kimura
Tominori
T
Laboratory of Microbiology and Cell Biology, Department of Pharmacy, College of Pharmaceutical Sciences, Ritsumeikan University, Kusatsu, Shiga 525-8577, Japan. kimurato@ph.ritsumei.ac.jp
Hashimoto
Iwao
I
Nishizawa
Mikio
M
Ito
Seiji
S
Yamada
Hisao
H
D021581:Active Transport, Cell Nucleus; D001483:Base Sequence; D002467:Cell Nucleus / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D016898:Interferon-alpha / Q000235:genetics*; D028884:Karyopherins / Q000235:genetics*; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D012333:RNA, Messenger / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics*; D012261:Ribonucleoproteins / Q000235:genetics / Q000378:metabolism; D000097606:Exportin 1 Protein
D016898:Interferon-alpha; D028884:Karyopherins; D012333:RNA, Messenger; D018160:Receptors, Cytoplasmic and Nuclear; D012261:Ribonucleoproteins; D000097606:Exportin 1 Protein; C554156:IFNA1 protein, human; C084538:RNPS1 protein, human