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Cellular junctions are essential to the normal functioning of the endothelium and control angiogenesis, tissue leak, and inflammation. From a screen of micro RNAs (miRNAs) altered in in vitro angiogenesis, we selected a subset predicted to target junctional molecules. MiR-27a was rapidly downregulated upon stimulation of in vitro angiogenesis, and its level of expression is reduced in neovessels in vivo. The downregulation of miR-27a was essential for angiogenesis because ectopic expression of miR-27a blocked capillary tube formation and angiogenesis. MiR-27a targets the junctional, endothelial-specific cadherin, VE-cadherin. Consistent with this, vascular permeability to vascular endothelial growth factor in mice is reduced by administration of a general miR-27 inhibitor. To determine that VE-cadherin was the dominant target of miR-27a function, we used a novel technology with "Blockmirs," inhibitors that bind to the miR-27 binding site in VE-cadherin. The Blockmir CD5-2 demonstrated specificity for VE-cadherin and inhibited vascular leak in vitro and in vivo. Furthermore, CD5-2 reduced edema, increased capillary density, and potently enhanced recovery from ischemic limb injury in mice. The Blockmir technology offers a refinement in the use of miRNAs, especially for therapy. Further, targeting of endothelial junctional molecules by miRNAs has clinical potential, especially in diseases associated with vascular leak.

Internal Ribosome Entry Sites (IRES) are cis-acting RNA sequences able to mediate internal entry of the 40S ribosomal subunit on some eukaryotic and viral messenger RNAs upstream of a translation initiation codon. These sequences are very diverse and are present in a growing list of mRNAs. Novel IRES sequences continue to be added to public databases every year and the list of unknown IRESes is certainly still very large. The IRES database is a comprehensive WWW resource for internal ribosome entry sites and presents currently available general information as well as detailed data for each IRES. It is a searchable, periodically updated collection of IRES RNA sequences. Sequences are presented in FASTA form and hotlinked to NCBI GenBank files. Several subsets of data are classified according to the viral taxon (for viral IRESes), to the gene product function (for cellular IRESes), to the possible cellular regulation or to the trans-acting factor that mediates IRES function. This database is accessible at http://ifr31w3.toulouse.inserm.fr/IRESdatabase/.

Tumour suppressor p53 has been shown to inhibit fibroblast 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 cis-acting elements to mediate the inhibitory effect 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 specifically 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 different RNAs showed no significant correlation between p53 RNA binding activity and its translational inhibiting effect. 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.