A single base exchange in an intron of the Dictyostelium discoideum alpha-actinin gene inhibits correct splicing of the RNA but allows transport to the cytoplasm and translation.
The genomic structure of the alpha-actinin gene from Dictyostelium discoideum has been determined. The coding region consists of three exons separated by two short introns located at either end of the gene. In an alpha-actinin mutant, HG1130, about 1% of alpha-actinin protein products are found compared to the parent strain AX2. The size of the mutant proteins are 88 and 95 kDa. In HG1130, the second intron is improperly spliced from the primary alpha-actinin transcript resulting from a mutation at the 5' splice site from a GT to an AT. The premature RNA is less efficiently cleaved at the mutated 5' splice site and the following step of the splicing reaction, ligation of exons 2 and 3, is prevented. Thus, two RNA species are generated, one in which intron 2 is not removed and one in which exon 2 is not ligated to exon 3. The two RNA species are stable, transported to the cytoplasm, bound to polysomes and translated. In vitro and in vivo, the partially spliced RNAs are translated into proteins of 88 and 95 kDa which can be immunoprecipitated with an alpha-actinin-specific monoclonal antibody. The in vivo stability of the mutant proteins is comparable to the wild type alpha-actinin.
Witke
W
W
Max-Planck-Institut für Biochemie, Martinsried, Federal Republic of Germany.
Noegel
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AA
D000185:Actinin / Q000235:genetics*; D001483:Base Sequence; D003593:Cytoplasm / Q000378:metabolism; D015342:DNA Probes; D004262:DNA Restriction Enzymes; D004023:Dictyostelium / Q000235:genetics* / Q000378:metabolism; D007438:Introns; D008969:Molecular Sequence Data; D009154:Mutation; D009693:Nucleic Acid Hybridization; D016133:Polymerase Chain Reaction; D011132:Polyribosomes / Q000378:metabolism; D014176:Protein Biosynthesis; D012326:RNA Splicing; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic / Q000235:genetics*
D015342:DNA Probes; D012333:RNA, Messenger; D000185:Actinin; D004262:DNA Restriction Enzymes