title: Evidence for differential ribonucleoprotein complex assembly in vitro on the 5'-untranslated region of the human IGF-IR transcript.
abstract: The type I insulin-like growth factor receptor (IGF-IR) plays a key role in the control of cellular proliferation and survival. The human IGF-IR transcript is characterized by an unusually long 1038 nucleotide 5'-untranslated region (5'-UTR). We hypothesized that the contribution of this complex 5'-untranslated RNA sequence to the post-transcriptional regulation of IGF-IR expression would involve a dynamic interplay between RNA structure and specific RNA-binding proteins. Here we have detected and characterized a diverse series of regulatory proteins binding the IGF-IR 5'-UTR under disparate conditions. One pair of proteins ( approximately 42/38 kDa) binds readily to the intact 5'-UTR, which is predicted to adopt a highly base-paired, highly favorable (dG=-498 kcal/mol) three-domain structure. Another protein(s) (p20*) specifically induces formation of a novel RNA structure from within the initial 209 nucleotides of the nascent IGF-IR transcript, but fails to UV crosslink to this RNA sequence. A third group of proteins recognizes and binds the IGF-IR 5'-UTR under highly stringent conditions, but only after higher-ordered RNA structure has been disrupted. Our in vitro results indicate that the IGF-IR 5'-UTR may exist in at least three distinct states, and we propose that interconversion between these states might take place in vivo and differentially alter IGF-IR transcript utilization.
authors.affiliation: The Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, 35294, USA.
authors.forename: Zheng
authors.initials: Z
authors.lastname: Meng
authors.forename: Richard C
authors.initials: RC
authors.lastname: Snyder
authors.forename: Kedar
authors.initials: K
authors.lastname: Shrestha
authors.forename: Donald M
authors.initials: DM
authors.lastname: Miller
authors.forename: Peter D
authors.initials: PD
authors.lastname: Emanuel
authors.forename: Scott W
authors.initials: SW
authors.lastname: Blume
mesh_terms: D020121:5' Untranslated Regions / Q000737:chemistry / Q000378:metabolism*; D001665:Binding Sites; D006801:Humans; D046911:Macromolecular Substances; D008957:Models, Genetic; D016601:RNA-Binding Proteins / Q000378:metabolism; D017526:Receptor, IGF Type 1 / Q000096:biosynthesis / Q000235:genetics*; D012045:Regulatory Sequences, Nucleic Acid; D012261:Ribonucleoproteins / Q000378:metabolism*
chemical_list: D020121:5' Untranslated Regions; D046911:Macromolecular Substances; D016601:RNA-Binding Proteins; D012261:Ribonucleoproteins; D017526:Receptor, IGF Type 1