A single internal ribosome entry site containing a G quartet RNA structure drives fibroblast growth factor 2 gene expression at four alternative translation initiation codons.
The 484-nucleotide (nt) alternatively translated region (ATR) of the human fibroblast growth factor 2 (FGF-2) mRNA contains four CUG and one AUG translation initiation codons. Although the 5'-end proximal CUG codon is initiated by a cap-dependent translation process, the other four initiation codons are initiated by a mechanism of internal entry of ribosomes. We undertook here a detailed analysis of the cis-acting elements defining the FGF-2 internal ribosome entry site (IRES). A thorough deletion analysis study within the 5'-ATR led us to define a 176-nt region as being necessary and sufficient for IRES function at four codons present in a downstream 308-nt RNA segment. Unexpectedly, a single IRES module is therefore responsible for translation initiation at four distantly localized codons. The determination of the FGF-2 5'-ATR RNA secondary structure by enzymatic and chemical probing experiments showed that the FGF-2 IRES contained two stem-loop regions and a G quartet motif that constitute novel structural determinants of IRES function.
Bonnal
Sophie
S
INSERM U589, Institut Louis Bugnard, Centre Hôpitalier Universitaire Rangueil, 31403 Toulouse cedex 04, France.
Schaeffer
Céline
C
Créancier
Laurent
L
Clamens
Simone
S
Moine
Hervé
H
Prats
Anne-Catherine
AC
Vagner
Stéphan
S
D017398:Alternative Splicing; D001483:Base Sequence; D002460:Cell Line; D018387:Codon, Initiator / Q000235:genetics; D018076:DNA, Complementary / Q000235:genetics; D016222:Fibroblast Growth Factor 2 / Q000235:genetics*; D015870:Gene Expression; D006801:Humans; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D010442:Peptide Chain Initiation, Translational; D012333:RNA, Messenger / Q000737:chemistry* / Q000235:genetics*; D012270:Ribosomes / Q000378:metabolism*; D017384:Sequence Deletion; D014162:Transfection
D018387:Codon, Initiator; D018076:DNA, Complementary; D012333:RNA, Messenger; D016222:Fibroblast Growth Factor 2