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.
Touriol
C
C
INSERM U397, Endocrinologie et Communication Cellulaire, Institut Louis Bugnard, Centre Hospitalier Universitaire de Rangueil, Avenue Jean Poulhès, 31403 Toulouse Cedex 04, France.
Morillon
A
A
Gensac
M C
MC
Prats
H
H
Prats
A C
AC
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