Translational regulation of platelet-derived growth factor B chain (c-sis) mRNA by short open reading frames in the 5'-untranslated region.
Platelet-derived growth factor B chain (PDGF-B/c-SIS), the product of c-sis proto-oncogene, is a potent mitogen and chemoattractant for cells of mesenchymal origin. Expression of PDGF-B/c-SIS is regulated at the translational level, in addition to at the transcriptional level. The 5'-untranslated region (5'-UTR) of PDGF-B/c-sis mRNA is known to inhibit translation of the downstream coding sequences. The 5'-UTR contains putative influential elements, such as GC-rich elements, stem-loop structures and short open reading frames (SORFs). To clarify the inhibition mechanism of PDGF-B/c-sis mRNA translation, effects of three SORFs in the 5'-UTR on the translational regulation were investigated in transient expression assays. Introducing point mutation(s) in the initiation codons of SORFs affected the reporter gene expression in several cell lines (COS-1, U-2, JEG-3). Abrogation of three SORFs resulted in an increase of the reporter gene expression both in beta-galactosidase assay and Western blot analysis. These results suggest that SORFs in the 5'-UTR sequences have inhibitory effects on the translation of the downstream coding sequences.
Laboratory of Animal Experiments, Hokkaido University, Sapporo, Japan.
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H
Nikami
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T
Kobayashi
T
T
Tasaki
S
S
Yoshino
S
S
Taharaguchi
E
E
Ono
D020121:5' Untranslated Regions / Q000235:genetics*; D000818:Animals; D019556:COS Cells; D015536:Down-Regulation / Q000235:genetics*; D017930:Genes, Reporter / Q000235:genetics; D006801:Humans; D016366:Open Reading Frames / Q000235:genetics*; D010982:Platelet-Derived Growth Factor / Q000235:genetics*; D014176:Protein Biosynthesis / Q000235:genetics*; D000090063:Proto-Oncogene Mas; D020574:Proto-Oncogene Proteins c-sis / Q000235:genetics*; D012333:RNA, Messenger / Q000378:metabolism*; D014162:Transfection; D014407:Tumor Cells, Cultured; D001616:beta-Galactosidase / Q000235:genetics
D020121:5' Untranslated Regions; C000715470:MAS1 protein, human; D010982:Platelet-Derived Growth Factor; D000090063:Proto-Oncogene Mas; D020574:Proto-Oncogene Proteins c-sis; D012333:RNA, Messenger; D001616:beta-Galactosidase