title: The mRNA export factor Dbp5 is associated with Balbiani ring mRNP from gene to cytoplasm.
abstract: The DEAD box RNA helicase Dbp5 is essential for nucleocytoplasmic transport of mRNA-protein (mRNP) complexes. Dbp5 is present mainly in the cytoplasm and is enriched at the cytoplasmic side of nuclear pore complexes (NPCs), suggesting that it acts in the late part of mRNP export. Here, we visualize the assembly and transport of a specific mRNP particle, the Balbiani ring mRNP in the dipteran Chironomus tentans, and show that a Dbp5 homologue in C.tentans, Ct-Dbp5, binds to pre-mRNP co-transcriptionally and accompanies the mRNP to and through the nuclear pores and into the cytoplasm. We also demonstrate that Ct-Dbp5 accumulates in the nucleus and partly disappears from the NPC when nuclear export of mRNA is inhibited. The fact that Ct-Dbp5 is present along the exiting mRNP fibril extending from the nuclear pore into the cytoplasm supports the view that Ct-Dbp5 is involved in restructuring the mRNP prior to translation. Finally, the addition of the export factor Dbp5 to the growing transcript highlights the importance of the co-transcriptional loading process in determining the fate of mRNA.
authors.affiliation: Department of Cell and Molecular Biology, Medical Nobel Institute, Karolinska Institutet, SE-17177 Stockholm, Sweden.
authors.forename: Jian
authors.initials: J
authors.lastname: Zhao
authors.forename: Shao-Bo
authors.initials: SB
authors.lastname: Jin
authors.forename: Birgitta
authors.initials: B
authors.lastname: Björkroth
authors.forename: Lars
authors.initials: L
authors.lastname: Wieslander
authors.forename: Bertil
authors.initials: B
authors.lastname: Daneholt
mesh_terms: D000251:Adenosine Triphosphatases / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D001692:Biological Transport; D002467:Cell Nucleus / Q000378:metabolism*; D002683:Chironomidae / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D002875:Chromosomes / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism*; D053487:DEAD-box RNA Helicases; D005690:Galactose / Q000494:pharmacology; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects; D006358:Hot Temperature; D006801:Humans; D019476:Insect Proteins / Q000235:genetics / Q000378:metabolism*; D007814:Larva; D008969:Molecular Sequence Data; D022022:Nuclear Pore / Q000378:metabolism; D029543:Nucleocytoplasmic Transport Proteins; D011485:Protein Binding; D020365:RNA Helicases; D012333:RNA, Messenger / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D012261:Ribonucleoproteins / Q000235:genetics / Q000378:metabolism*; D012469:Salivary Glands / Q000187:drug effects / Q000378:metabolism; D012471:Salivary Proteins and Peptides / Q000235:genetics / Q000378:metabolism*; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013045:Species Specificity; D013312:Stress, Physiological / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects
chemical_list: D019476:Insect Proteins; D029543:Nucleocytoplasmic Transport Proteins; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D012261:Ribonucleoproteins; D012471:Salivary Proteins and Peptides; C026452:messenger ribonucleoprotein; D000251:Adenosine Triphosphatases; C121148:DDX19B protein, human; D053487:DEAD-box RNA Helicases; D020365:RNA Helicases; D005690:Galactose