The 5' untranslated sequence of the c-sis/platelet-derived growth factor 2 transcript is a potent translational inhibitor.

Abstract

c-sis/platelet-derived growth factor 2 (PDGF-2) is a prototype growth factor with transforming potential. The c-sis/PDGF-2 transcript contains a long 5' untranslated sequence (UTS) that is highly G.C rich. To examine the influence of this sequence on sis/PDGF-2 expression, we localized the c-sis/PDGF-2 promoter and used this promoter or the simian virus 40 early promoter to drive expression of the bacterial chloramphenicol acetyltransferase or sis/PDGF-2 gene. The 5' UTS of c-sis/PDGF-2 mRNA had no effect on RNA expression but was shown to exert a potent inhibitory effect on translation. By deletion analysis, we demonstrated that the 5' UTS inhibited protein expression by as much as 40-fold. The inhibitory effect was independent of reporter gene, cell type, or promoter used. A highly G.C-rich 140-base-pair sequence immediately preceding the c-sis/PDGF-2 initiation codon was shown to be nearly as effective as the entire 5' UTS in translational inhibition. Transfection analysis demonstrated that the 5' UTS significantly reduced the transforming efficiency of the sis/PDGF-2 gene as well. Thus, our findings raise the possibility that changes in regulation at the level of sis/PDGF-2 translation may play a role in development of the neoplastic phenotype.

Normal developing rat brain expresses a platelet-derived growth factor B chain (c-sis) mRNA truncated at the 5′ end

“…The currently determined rat PDGF-B/c-sis cDNA contained a 5' UTS highly homologous with that of human (79.2%, Rao et al, 1988) and mouse (95.4%, Bonthoron et al, 1991). Similar to other species, the rat message contained four ATG translation initiation codons (Figure 1…”

“…The 5' UTS of PDGF-B/c-sis has been reported to strongly inhibit translation (Rao et al, 1988). A recent deletion mutation study demonstrated that a strong stem-loop structure, as well as GC-rich element, were required to block PDGF-B/c-sis mRNA translation (Horvath et al, 1995).…”

“…This transcript possesses an unusual feature, a 1 kb-long 5' untranslated sequence (UTS), which plays an important role in translational inhibition, and is presumed to be important for post-transcriptional control (Rao et al, 1988). Expression of a shorter, 2.8 kb PDGF-B/c-sis transcript, which lacks the 5' UTS, has been described in cultured human umbilical vein endothelial cells (HUVECs;Fen and Daniel, 1991).…”

Regulation of constitutive expression of mouse PTEN by the 5′-untranslated region

“…A transcript with a 5 0 -UTR of only 93 bases is 100-fold more translatable than the transcript with a long 5 0 -UTR of 828 bases. The inhibitory effect of the long 5 0 -UTR is similar to that of the 5 0 -UTR of PDGF, which inhibits translation about 40-fold (Rao et al, 1988). Inhibition of translation by 5 0 -UTR led us to explore other mechanisms such as IRES that may be used for PTEN translation.…”

Structure and organization of the gene encoding a mouse mitochondrial stress‐70 protein

“…Computer-aided analysis of this sequence demonstrates a stable secondary structure, as described above. Other genes for TGF-b1 [31], TGF-B3 [32], ferritin [33,34], and c-.&platelet-derived growth factor 2 [35,36] have been reported to contain the similar sequence with the stable secondary structure in the S-untranslated region, which acts as a translation regulator [37,38]. Thus, further experiments are required to elucidate the regulatory mechanism of expression of the PBP741CSA gene.…”