title: An RNA electrophoretic mobility shift and mutational analysis of rnp-4f 5'-UTR intron splicing regulatory proteins in Drosophila reveals a novel new role for a dADAR protein isoform.
abstract: Alternative splicing greatly enhances the diversity of proteins encoded by eukaryotic genomes, and is also important in gene expression control. In contrast to the great depth of knowledge as to molecular mechanisms in the splicing pathway itself, relatively little is known about the regulatory events behind this process. The 5'-UTR and 3'-UTR in pre-mRNAs play a variety of roles in controlling eukaryotic gene expression, including translational modulation, and nearly 4000 of the roughly 14,000 protein coding genes in Drosophila contain introns of unknown functional significance in their 5'-UTR. Here we report the results of an RNA electrophoretic mobility shift analysis of Drosophila rnp-4f 5'-UTR intron 0 splicing regulatory proteins. The pre-mRNA potential regulatory element consists of an evolutionarily-conserved 177-nt stem-loop arising from pairing of intron 0 with part of adjacent exon 2. Incubation of in vitro transcribed probe with embryo protein extract is shown to result in two shifted RNA-protein bands, and protein extract from a dADAR null mutant fly line results in only one shifted band. A mutated stem-loop in which the conserved exon 2 primary sequence is changed but secondary structure maintained by introducing compensatory base changes results in diminished band shifts. To test the hypothesis that dADAR plays a role in intron splicing regulation in vivo, levels of unspliced rnp-4f mRNA in dADAR mutant were compared to wild-type via real-time qRT-PCR. The results show that during embryogenesis unspliced rnp-4f mRNA levels fall by up to 85% in the mutant, in support of the hypothesis. Taken together, these results demonstrate a novel role for dADAR protein in rnp-4f 5'-UTR alternative intron splicing regulation which is consistent with a previously proposed model.
authors.affiliation: Department of Zoology, Cell Molecular and Structural Biology Program, Miami University, Oxford, OH 45056, USA.
authors.forename: G Girija
authors.initials: GG
authors.lastname: Lakshmi
authors.forename: Sushmita
authors.initials: S
authors.lastname: Ghosh
authors.forename: Gabriel P
authors.initials: GP
authors.lastname: Jones
authors.forename: Roshni
authors.initials: R
authors.lastname: Parikh
authors.forename: Bridgette A
authors.initials: BA
authors.lastname: Rawlins
authors.forename: Jack C
authors.initials: JC
authors.lastname: Vaughn
mesh_terms: D020121:5' Untranslated Regions; D000243:Adenosine Deaminase / Q000502:physiology*; D000818:Animals; D001483:Base Sequence; D029721:Drosophila Proteins / Q000502:physiology*; D004331:Drosophila melanogaster / Q000235:genetics*; D024202:Electrophoretic Mobility Shift Assay / Q000379:methods*; D007438:Introns; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D020033:Protein Isoforms / Q000502:physiology*; D012313:RNA / Q000737:chemistry / Q000235:genetics; D012326:RNA Splicing; D060888:Real-Time Polymerase Chain Reaction; D012689:Sequence Homology, Nucleic Acid
chemical_list: D020121:5' Untranslated Regions; D029721:Drosophila Proteins; D020033:Protein Isoforms; D012313:RNA; C567956:Adar protein, Drosophila; D000243:Adenosine Deaminase