The interaction between cap-binding complex and RNA export factor is required for intronless mRNA export.
RNA export factor (REF) is a component of the exon junction complex (EJC) that is deposited on mRNA in a splicing-dependent manner, and targets spliced mRNA for export. In this study, analysis of the RNA-binding protein complexes revealed that REF associates with beta-globin mRNA at the region other than the EJC deposition site. Comparison between RNA polymerase II and T7 transcription and further analysis showed that the deposition of REF apart from the EJC is dependent on the 5' cap structure, but not splicing. Excess amounts of m(7)GpppG cap analog reduced REF binding to intronless mRNA, and a co-immunoprecipitation experiment revealed that REF interacts with the cap-binding protein CBP20. The export of Cy3-labeled intronless beta-globin mRNA from nuclei of HeLa cells was enhanced by co-injection of CBP20 and REF. Thus, REF recruited by CBP20 may play a stimulatory role to export the capped intronless mRNAs.
Nojima
Takayuki
T
Laboratory of Gene Expression, School of Biomedical Science, Tokyo Medical and Dental University, Yushima 1-5-45, Bunkyo-ku, Japan.
Hirose
Tetsuro
T
Kimura
Hiroshi
H
Hagiwara
Masatoshi
M
D012321:DNA-Directed RNA Polymerases / Q000737:chemistry / Q000378:metabolism; D015226:Dinucleoside Phosphates / Q000737:chemistry / Q000378:metabolism; D005914:Globins; D006801:Humans; D039502:Nuclear Cap-Binding Protein Complex / Q000737:chemistry / Q000378:metabolism*; D029543:Nucleocytoplasmic Transport Proteins / Q000737:chemistry / Q000378:metabolism*; D012315:RNA Caps / Q000737:chemistry / Q000378:metabolism*; D012319:RNA Polymerase II / Q000737:chemistry / Q000378:metabolism; D012326:RNA Splicing / Q000502:physiology; D034443:RNA Transport / Q000502:physiology*; D014158:Transcription, Genetic; D014764:Viral Proteins / Q000737:chemistry / Q000378:metabolism
D015226:Dinucleoside Phosphates; D039502:Nuclear Cap-Binding Protein Complex; D029543:Nucleocytoplasmic Transport Proteins; D012315:RNA Caps; D014764:Viral Proteins; C062229:7-methyl-diguanosine triphosphate; D005914:Globins; D012319:RNA Polymerase II; C062210:bacteriophage T7 RNA polymerase; D012321:DNA-Directed RNA Polymerases