Expression of human fibroblast growth factor 2 mRNA is post-transcriptionally controlled by a unique destabilizing element present in the 3'-untranslated region between alternative polyadenylation sites.
Fibroblast growth factor 2 (FGF-2) belongs to a family of 18 genes coding for either mitogenic differentiating factors or oncogenic proteins, the expression of which must be tightly controlled. We looked for regulatory elements in the 5823-nucleotide-long 3'-untranslated region of the FGF-2 mRNA that contains eight potential alternative polyadenylation sites. Quantitative reverse transcription-polymerase chain reaction revealed that poly(A) site utilization was cell type-dependent, with the eighth poly(A) site being used (95%) in primary human skin fibroblasts, whereas proximal sites were used in the transformed cell lines studied here. We used a cell transfection approach with synthetic reporter mRNAs to localize a destabilizing element between the first and second poly(A) sites. Although AU-rich, the FGF-2-destabilizing element had unique features: it involved a 122-nucleotide direct repeat, with both elements of the repeat being required for the destabilizing activity. These data show that short stable FGF-2 mRNAs are present in transformed cells, whereas skin fibroblasts contain mostly long unstable mRNAs, suggesting that FGF-2 mRNA stability cannot be regulated in transformed cells. The results also provide evidence of a multilevel post-transcriptional control of FGF-2 expression; such a stringent control prevents FGF-2 overexpression and permits its expression to be enhanced only in relevant physiological situations.
INSERM U397, Endocrinologie et Communication Cellulaire, Institut Louis Bugnard, Centre Hospitalier Universitaire de Rangueil, Avenue Jean Poulhès, 31403 Toulouse Cedex 04, France.
C
C
Touriol
A
A
Morillon
M C
MC
Gensac
H
H
Prats
A C
AC
Prats
D020413:3' Untranslated Regions / Q000235:genetics; D000249:Adenosine Monophosphate; D000818:Animals; D001483:Base Sequence; D019556:COS Cells; D016222:Fibroblast Growth Factor 2 / Q000096:biosynthesis* / Q000235:genetics; D006367:HeLa Cells; D006801:Humans; D008969:Molecular Sequence Data; D010957:Plasmids; D011499:Protein Processing, Post-Translational; D012333:RNA, Messenger / Q000096:biosynthesis* / Q000235:genetics; D014162:Transfection
D020413:3' Untranslated Regions; D012333:RNA, Messenger; D016222:Fibroblast Growth Factor 2; D000249:Adenosine Monophosphate