title: A hairpin-like structure within an AU-rich mRNA-destabilizing element regulates trans-factor binding selectivity and mRNA decay kinetics.
abstract: In mammals, rapid mRNA turnover directed by AU-rich elements (AREs) is mediated by selective association of cellular ARE-binding proteins. These trans-acting factors display overlapping RNA substrate specificities and may act to either stabilize or destabilize targeted transcripts; however, the mechanistic features of AREs that promote preferential binding of one trans-factor over another are not well understood. Here, we describe a hairpin-like structure adopted by the ARE from tumor necrosis factor alpha (TNFalpha) mRNA that modulates its affinity for selected ARE-binding proteins. In particular, association of the mRNA-destabilizing factor p37(AUF1) was strongly inhibited by adoption of the higher order ARE structure, whereas binding of the inducible heat shock protein Hsp70 was less severely compromised. By contrast, association of the mRNA-stabilizing protein HuR was only minimally affected by changes in ARE folding. Consistent with the inverse relationship between p37(AUF1) binding affinity and the stability of ARE folding, mutations that stabilized the ARE hairpin also inhibited its ability to direct rapid mRNA turnover in transfected cells. Finally, phylogenetic analyses and structural modeling indicate that TNFalpha mRNA sequences flanking the ARE are highly conserved and may stabilize the hairpin fold in vivo. Taken together, these data suggest that local higher order structures involving AREs may function as potent regulators of mRNA turnover in mammalian cells by modulating trans-factor binding selectivity.
authors.affiliation: Department of Biochemistry and Molecular Biology and Center for Fluorescence Spectroscopy, University of Maryland School of Medicine, 108 N. Greene Street, Baltimore, MD 21201, USA.
authors.forename: Elizabeth J
authors.initials: EJ
authors.lastname: Fialcowitz
authors.forename: Brandy Y
authors.initials: BY
authors.lastname: Brewer
authors.forename: Bridget P
authors.initials: BP
authors.lastname: Keenan
authors.forename: Gerald M
authors.initials: GM
authors.lastname: Wilson
mesh_terms: D001483:Base Sequence; D002412:Cations; D019295:Computational Biology; D018076:DNA, Complementary / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D031541:Fluorescence Resonance Energy Transfer; D005982:Glutathione Transferase / Q000378:metabolism; D018840:HSP70 Heat-Shock Proteins / Q000737:chemistry; D000081035:Heterogeneous Nuclear Ribonucleoprotein D0; D034502:Heterogeneous-Nuclear Ribonucleoprotein D / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D008274:Magnesium / Q000737:chemistry; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D009690:Nucleic Acid Conformation; D010802:Phylogeny; D011485:Protein Binding; D017510:Protein Folding; D012313:RNA / Q000737:chemistry; D012333:RNA, Messenger / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry; D012689:Sequence Homology, Nucleic Acid; D013696:Temperature; D013997:Time Factors; D014162:Transfection; D014409:Tumor Necrosis Factor-alpha / Q000737:chemistry*
chemical_list: D002412:Cations; D018076:DNA, Complementary; C000630986:HNRNPD protein, human; D018840:HSP70 Heat-Shock Proteins; D000081035:Heterogeneous Nuclear Ribonucleoprotein D0; D034502:Heterogeneous-Nuclear Ribonucleoprotein D; D012333:RNA, Messenger; D011994:Recombinant Proteins; D014409:Tumor Necrosis Factor-alpha; D012313:RNA; D005982:Glutathione Transferase; D008274:Magnesium