The presence in the mRNA of premature
stop codons (PTCs) results
in protein truncation responsible for several inherited (genetic)
diseases. A well-known example of these diseases is cystic fibrosis
(CF), where approximately 10% (worldwide) of patients have nonsense
mutations in the CF transmembrane regulator (CFTR) gene. PTC124 (3-(5-(2-fluorophenyl)-1,2,4-oxadiazol-3-yl)-benzoic
acid), also known as Ataluren, is a small molecule that has been suggested
to allow PTC readthrough even though its target has yet to be identified.
In the lack of a general consensus about its mechanism of action,
we experimentally tested the ability of PTC124 to promote the readthrough
of premature termination codons by using a new reporter. The reporter
vector was based on a plasmid harboring the H2B histone coding sequence
fused in frame with the green fluorescent protein (GFP) cDNA, and
a TGA stop codon was introduced in the H2B-GFP gene by site-directed
mutagenesis. Additionally, an unprecedented computational study on
the putative supramolecular interaction between PTC124 and an 11-codon
(33-nucleotides) sequence corresponding to a CFTR mRNA fragment containing
a central UGA nonsense mutation showed a specific interaction between
PTC124 and the UGA codon. Altogether, the H2B-GFP-opal based assay
and the molecular dynamics (MD) simulation support the hypothesis
that PTC124 is able to promote the specific readthrough of internal
TGA premature stop codons.