Opposing activities of c-Fos and Fra-2 on AP-1 regulated transcriptional activity in mouse keratinocytes induced to differentiate by calcium and phorbol esters.
The major differentiation products of maturing keratinocytes contain AP-1 regulatory motifs, and AP-1 DNA binding activity increases in cultured keratinocytes induced to differentiate by calcium. Here, we have analysed AP-1 transcriptional activity in mouse keratinocytes treated with calcium and 12-O-tetradecanoyl phorbol-13-acetate (TPA), two agents that induce terminal differentiation of keratinocytes with different phenotypic consequences. Reporter constructs representing multimers of AP-1 sequences found in keratinocyte marker genes demonstrated that the calcium-induced AP-1 DNA binding activity does not correlate with transcriptional activation. Moreover, expression from active subunits of the profilaggrin and spr 1 promoters increased in calcium-treated keratinocytes when the AP-1 sites were disrupted, indicating that AP-1 may negatively regulate certain promoters in these cells. In contrast, AP-1 reporter activity was increased in keratinocytes treated with TPA. This induction was dependent upon the expression of c-Fos since AP-1 transcriptional activity was not increased in TPA-treated keratinocytes derived from c-fos null mice. Analysis of AP-1 protein expression in calcium- and TPA-treated keratinocytes demonstrated that only TPA increased the expression of c-Jun, while Jun B and Jun D were induced by both of these agents. c-Fos was expressed only in TPA treated keratinocytes, Fra-2 was expressed only in calcium-treated cells, and Fra-1 was expressed in both. Exogenous expression of Fra-2 repressed AP-1 transcriptional activity in TPA-treated keratinocytes, while c-Fos expression activated the AP-1 sequence in calcium-treated keratinocytes. These data indicate that Fra-2 and c-Fos play opposing roles in regulating AP-1 activity in keratinocytes and that multiple inducer-dependent regulatory pathways may exist for the expression of keratinocyte differentiation markers.
Rutberg
S E
SE
Laboratory of Cellular Carcinogenesis and Tumor Promotion, National Cancer Institute, Bethesda, Maryland 20892, USA.
Saez
E
E
Lo
S
S
Jang
S I
SI
Markova
N
N
Spiegelman
B M
BM
Yuspa
S H
SH
D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D002118:Calcium / Q000494:pharmacology; D002454:Cell Differentiation / Q000187:drug effects* / Q000235:genetics; D004268:DNA-Binding Proteins / Q000187:drug effects / Q000235:genetics*; D000091344:Filaggrin Proteins; D051921:Fos-Related Antigen-2; D005786:Gene Expression Regulation; D016762:Genes, fos; D007381:Intermediate Filament Proteins / Q000235:genetics / Q000378:metabolism; D015603:Keratinocytes / Q000187:drug effects / Q000378:metabolism*; D051379:Mice; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D011498:Protein Precursors / Q000235:genetics / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D018808:Transcription Factor AP-1 / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000187:drug effects / Q000235:genetics*; D015533:Transcriptional Activation
D004268:DNA-Binding Proteins; D000091344:Filaggrin Proteins; D051921:Fos-Related Antigen-2; C497873:Fosl2 protein, mouse; D007381:Intermediate Filament Proteins; D011498:Protein Precursors; D018808:Transcription Factor AP-1; D014157:Transcription Factors; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium