Fos-related antigen 2 controls protein kinase A-induced CCAAT/enhancer-binding protein beta expression in osteoblasts.
Transcription factor CCAAT/enhancer-binding protein beta (C/EBPbeta) plays an important role in hormone-dependent gene expression. In osteoblasts C/EBPbeta can increase insulin-like growth factor I (IGF-I) transcription following treatment with hormones that activate protein kinase A, but little is known as yet about the expression of C/EBPbeta itself in these cells. We initially showed that prostaglandin E2 (PGE2) rapidly enhances C/EBPbeta mRNA and protein expression, and in this study we identified a 3'-proximal region of the C/EBPbeta promoter containing a 541-bp upstream sequence that could account for this effect. PGE2-dependent activation of C/EBPbeta was blocked by expression of a mutated regulatory subunit of protein kinase A or by mutation of two previously identified cAMP-sensitive cis-acting regulatory elements within the promoter between bp -111 and -61. Nuclear protein binding to these elements was induced by PGE2, required new protein synthesis, and was sensitive to antibody to the transcription factor termed Fos-related antigen 2 (Fra-2). Fra-2 cDNA generated from rat osteoblasts by reverse transcriptase PCR was 95% homologous to human Fra-2, and PGE2 rapidly induced Fra-2 mRNA and protein expression. Consistent with these findings, over-expression of Fra-2 significantly increased C/EBPbeta promoter activity in PGE2-induced osteoblasts, whereas expression of Fra-2 lacking its activation domain had a dominant negative inhibitory effect. Together, these results reveal a significant, hormone-dependent role for Fra-2 in osteoblast function, both directly, through its ability to increase new C/EBPbeta gene expression, and indirectly, through downstream C/EBP sensitive genes.
Section of Plastic Surgery, Department of Surgery, Yale University School of Medicine, New Haven, Connecticut 06520, USA.
Weizhong
W
Chang
Amar
A
Rewari
Michael
M
Centrella
Thomas L
TL
McCarthy
D000595:Amino Acid Sequence; D000818:Animals; D015153:Blotting, Western; D022782:CCAAT-Enhancer-Binding Protein-beta / Q000096:biosynthesis*; D019556:COS Cells; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D016895:Culture Media, Serum-Free; D000242:Cyclic AMP / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D018076:DNA, Complementary / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D051921:Fos-Related Antigen-2; D005786:Gene Expression Regulation; D005799:Genes, Dominant; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D008954:Models, Biological; D008969:Molecular Sequence Data; D009154:Mutation; D010006:Osteoblasts / Q000378:metabolism*; D010957:Plasmids / Q000378:metabolism; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012313:RNA / Q000737:chemistry / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors / Q000378:metabolism / Q000502:physiology*; D014162:Transfection
D022782:CCAAT-Enhancer-Binding Protein-beta; D016895:Culture Media, Serum-Free; D018076:DNA, Complementary; D004268:DNA-Binding Proteins; C497872:FOSL2 protein, human; D051921:Fos-Related Antigen-2; C497874:Fosl2 protein, rat; D012333:RNA, Messenger; D014157:Transcription Factors; D012313:RNA; D007334:Insulin-Like Growth Factor I; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases