p53 directs conformational change and translation initiation blockade of human fibroblast growth factor 2 mRNA

Abstract

Tumour suppressor p53 has been shown to inhibit ®broblast growth factor 2 expression post-transcriptionally in cultured cells. Here we have investigated the mechanism responsible for this post-transcriptional blockade. Deletion mutagenesis of the FGF-2 mRNA leader revealed the requirement of at least four RNA cisacting elements to mediate the inhibitory e ect of p53 in SK-Hep-1 transfected cells, suggesting the involvement of RNA secondary or tertiary structures. Recombinant wild-type, but not Ala 143 mutant p53, was able to speci®cally repress FGF-2 mRNA translation in rabbit reticulocyte lysate, in a dose dependent manner. Sucrose gradient experiments showed that p53 blocks translation initiation by preventing 80S ribosome formation on an mRNA bearing the FGF-2 mRNA leader sequence. Interaction of wild-type and mutant p53 with di erent RNAs showed no signi®cant correlation between p53 RNA binding activity and its translational inhibiting e ect. However, by checking the accessibility of the FGF-2 mRNA leader to complementary oligonucleotide probes, we showed that the binding to RNA of wild-type, but not mutant p53, induced RNA conformational changes that might be responsible for the translational blockade. This strongly suggests that p53 represses FGF-2 mRNA translation by a direct mechanism involving its nucleic acid unwinding ± annealing activity. Oncogene (2001) 20, 4613 ± 4620.

FGF1 inhibits p53-dependent apoptosis and cell cycle arrest via an intracrine pathway

“…Within the FGF family, p53 has been shown to inhibit fgf2 gene expression at the transcriptional level, but the fgf2 promoter does not contain either a typical TATA box or a p53-DNA-binding consensus sequence (Ueba et al, 1994). It has also been reported that p53 inhibits fgf2 expression at posttranscriptional levels, by blocking the initiation of translation of human fgf2 mRNA (Galy et al, 2001a, b). fgf1 expression is mainly regulated at the transcriptional level: different promoters, alternative splicing and multiple polyadenylation signals generate different fgf1 transcripts (Crumley et al, 1989;Philippe et al, 1992Philippe et al, , 1996Renaud et al, 1992;Chiu et al, 2001).…”

Mapping and characterization of the minimal internal ribosome entry segment in the human c-myc mRNA 5′ untranslated region

“…While viral IRESes participate in a mechanism aimed at the misappropriation of the cellular translational machinery from cellular mRNAs, cellular IRESes allow the expression of certain mRNAs in conditions in which cap-dependent translation initiation is severely impaired. RNA conformation is thought to be critical for the activity of several viral and cellular IRESes (Kaminski et al, 1990;Galy et al, 2001;Mitchell et al, 2003). Here, we show that c-myc P2 mRNA 5 0 UTR is predicted to fold in a Y-shaped secondary structure characteristic of viral IRESes (Le et al, 1996) (Figure 1).…”

“…Moreover, c-myc IRES activity is observed in apoptotic cells, during the G2/M transition of the cell cycle and upon genotoxic stress, conditions in which cap-dependent translation is severely impaired (Pyronnet et al, 2000;Stoneley et al, 2000;Subkhankulova et al, 2001). In vivo, the c-myc IRES is mainly active during embryogenesis, and is downregulated at later stages of development (Cre´ancier et al, 2001).…”

Efficient gene transfer in skeletal muscle with AAV-derived bicistronic vector using the FGF-1 IRES

“…29 In addition, p53, which is able to inhibit the FGF-2 IRES activity, also acts by modifying the RNA structure. 33 Thus, we can hypothesize that ITAFs may also act on mRNA stability: if the mRNA is highly structured, it may presumably render it more resistant to RNAses. p53 is probably not responsible for the FGF-1 IRES inhibition in 911 cells, as these cells express the adenovirus E1 protein that complexes and inactivates p53.…”