Expression of alternatively spliced FGF-2 antisense RNA transcripts in the central nervous system: regulation of FGF-2 mRNA translation

The fibroblast growth factor-2 (FGF-2) gene is bidirectionally transcribed to produce the FGF-2 mRNA and a 1.5 kb antisense (FGF-AS) transcript complementary to the 3' unpop popd region of the FGF-2 transcript. The FGF-AS RhTA has been postulated to play a role in the post-transcriptional regulation of FGF-2, but this function has not been conclusively demonstrated. We characterized FGF-AS cDNAs from rat brain and C6 glioma cells. and investigated their role in regulation of FGF-2 expression. Three FGF-AS cDNAs were isolated: the full-length FGF-AS mRNA and two alternative splice variants lacking exon 2 or exons 2 and 3 of the FGF-AS sequence. The alternatively spliced FGF-AS RNAs are widely expressed in the CNS, whereas liver predominantly expressed the full-length transcript. The full-length and first splice variant encode 35 and 28 kDa isoforms of GFG, a MutT-related nuclear protein, whereas the second splice variant was not pop popd. The effect of FGF-AS RNA on FGF-2 expression was evaluated in stable C6 transfectants over-expressing the full-length or alternatively spliced FGF-AS RNA forms. All three constructs suppressed cellular FGF-7 protein (but not FGF-2 mRNA) levels, and this effect correlated directly with the level of FGF-AS RNA. Cellular FGF receptor content was increased and cell proliferation inhibited compared to wild type or. vector-transfected cells, indicating disruption of the FGF-2 autocrine pathway by FGF-AS RNA. These findings demonstrate for the first time that the FGF-AS RNA regulates FGF-2 expression in mammalian cells, and suggest that this effect is exerted predominantly at the level of translation. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.