title: Constitutive translation of human α-synuclein is mediated by the 5'-untranslated region.
abstract: Genetic and biochemical studies have established a central role for α-synuclein (SNCA) accumulation in the pathogenesis of Parkinson's disease. Uncovering and subsequently interfering with physiological mechanisms that control SNCA expression is one approach to limit disease progression. To this end, the long and GC-rich 5'-untranslated region (UTR) of SNCA, which is predicted to fold into stable hairpin and G-quadruplex RNA motifs, was investigated for its role in mRNA translation. Inclusion of SNCA 5'-UTR significantly induced expression of both SNCA and luciferase ORF constructs. This effect was not associated with a change in mRNA levels or differential nucleocytoplasmic shuttling. Further, the presence of the 5'-UTR enhanced SNCA synthesis when cap-dependent translation was attenuated with rapamycin treatment. Analysis using multiple methodologies revealed that the 5'-UTR harbours an internal ribosome entry site (IRES) element that spans most of its nucleotide sequence. Signals such as plasma-membrane depolarization, serum starvation and oxidative stress stimulated SNCA protein translation via its 5'-UTR as well as enhanced its IRES activity. Taken together, these data support the idea that the 5'-UTR is an important positive regulator of SNCA synthesis under diverse physiological and pathological conditions, explaining in part the abundance of SNCA in healthy neurons and its accumulation in degenerative cells.
authors.affiliation: Division of Basic Sciences, Biomedical Research Foundation, Academy of Athens, Athens, Attiki 11527, Greece.
authors.forename: Pelagia
authors.initials: P
authors.lastname: Koukouraki
authors.affiliation: Division of Basic Sciences, Biomedical Research Foundation, Academy of Athens, Athens, Attiki 11527, Greece edoxakis@bioacademy.gr.
authors.forename: Epaminondas
authors.initials: E
authors.lastname: Doxakis
mesh_terms: D020121:5' Untranslated Regions / Q000235:genetics*; D001483:Base Sequence; D002467:Cell Nucleus / Q000378:metabolism; D019295:Computational Biology; D054856:G-Quadruplexes; D017930:Genes, Reporter; D057809:HEK293 Cells; D006801:Humans; D000067556:Internal Ribosome Entry Sites / Q000235:genetics; D008156:Luciferases / Q000378:metabolism; D016366:Open Reading Frames / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000235:genetics; D014176:Protein Biosynthesis; D021381:Protein Transport; D012315:RNA Caps / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012270:Ribosomes / Q000378:metabolism; D013312:Stress, Physiological / Q000235:genetics; D051844:alpha-Synuclein / Q000235:genetics* / Q000378:metabolism
chemical_list: D020121:5' Untranslated Regions; D000067556:Internal Ribosome Entry Sites; D012315:RNA Caps; D012333:RNA, Messenger; C497604:SNCA protein, human; D051844:alpha-Synuclein; D008156:Luciferases
keywords: 5′-UTR; G-quadruplex; Parkinson's disease; internal ribosome entry site; iron-responsive element; α-synuclein