The DEAD-box Protein Dbp2 Functions with the RNA-Binding Protein Yra1 to Promote mRNP Assembly

• Published in: Journal of molecular biology 2013-10, Vol.425 (20), p.3824-3838
• Main Authors: Ma, Wai Kit, Cloutier, Sara C., Tran, Elizabeth J.
• Format: Article
• Language: English
• Subjects: Adenosine Triphosphate - metabolism; Catalysis; co-transcriptional; DEAD-box RNA Helicases - genetics; DEAD-box RNA Helicases - metabolism; Epistasis, Genetic; eukaryotic cells; gene expression; genes; messenger RNA; metabolism; mRNP remodeling; Nuclear Proteins - genetics; Nuclear Proteins - metabolism; Nucleic Acid Conformation; Nucleocytoplasmic Transport Proteins - genetics; Nucleocytoplasmic Transport Proteins - metabolism; Protein Binding; Ribonucleoproteins - metabolism; RNA annealing; RNA helicases; RNA unwinding; RNA, Fungal - chemistry; RNA, Fungal - genetics; RNA, Fungal - metabolism; RNA, Messenger - genetics; RNA, Messenger - metabolism; RNA-binding proteins; RNA-Binding Proteins - genetics; RNA-Binding Proteins - metabolism; Saccharomyces cerevisiae; Saccharomyces cerevisiae - genetics; Saccharomyces cerevisiae - metabolism; Saccharomyces cerevisiae Proteins - genetics; Saccharomyces cerevisiae Proteins - metabolism
• ISSN: 0022-2836; 1089-8638
• DOI: 10.1016/j.jmb.2013.05.016

Eukaryotic gene expression involves numerous biochemical steps that are dependent on RNA structure and ribonucleoprotein (RNP) complex formation. The DEAD-box class of RNA helicases plays fundamental roles in formation of RNA and RNP structure in every aspect of RNA metabolism. In an effort to explore the diversity of biological roles for DEAD-box proteins, our laboratory recently demonstrated that the DEAD-box protein Dbp2 associates with actively transcribing genes and is required for normal gene expression in Saccharomyces cerevisiae. We now provide evidence that Dbp2 interacts genetically and physically with the mRNA export factor Yra1. In addition, we find that Dbp2 is required for in vivo assembly of mRNA-binding proteins Yra1, Nab2, and Mex67 onto poly(A)+ RNA. Strikingly, we also show that Dbp2 is an efficient RNA helicase in vitro and that Yra1 decreases the efficiency of ATP-dependent duplex unwinding. We provide a model whereby messenger ribonucleoprotein (mRNP) assembly requires Dbp2 unwinding activity and once the mRNP is properly assembled, inhibition by Yra1 prevents further rearrangements. Both Yra1 and Dbp2 are conserved in multicellular eukaryotes, suggesting that this constitutes a broadly conserved mechanism for stepwise assembly of mature mRNPs in the nucleus. [Display omitted] •The DEAD-box RNA helicase Dbp2 from S. cerevisiae efficiently unwinds RNA duplexes.•Loss of DBP2 in yeast cells results in defective assembly of nuclear mRNPs.•Loading of Yra1, Nab2, and Mex67 into mRNPs requires DBP2.•Yra1 interacts directly with Dbp2 and also inhibits RNA-duplex unwinding.•A model for unwinding of structured, nascent mRNA prior to mRNP assembly is shown.