AP-2 transcription factor family member expression, activity, and regulation in human epidermal keratinocytes in vitro.
The AP-2 transcription factor family is presumed to play an important role in the regulation of the keratinocyte squamous differentiation program; however, limited functional data are available to support this. In the present study, the activity and regulation of AP-2 were examined in differentiating human epidermal keratinocytes. We report that (1) AP-2 transcriptional activity decreases in differentiated keratinocytes but remains unchanged in differentiation-insensitive squamous cell carcinoma cell lines, (2) diminished AP-2 transcriptional activity is associated with a loss of specific DNA-bound AP-2 complexes, and (3) there is an increase in the ability of cytoplasmic extracts, derived from differentiated keratinocytes, to phosphorylate AP-2 alpha and AP-2 beta when cells differentiate. In contrast, extracts from differentiation-insensitive squamous cell carcinoma cells are unable to phosphorylate AP-2 proteins. Finally, the phosphorylation of recombinant AP-2 alpha by cytosolic extracts from differentiated keratinocytes is associated with decreased AP-2 DNA-binding activity. Combined, these data indicate that AP-2 trans-activation and DNA-binding activity decrease as keratinocytes differentiate, and that this decreased activity is associated with an enhanced ability to phosphorylate AP-2 alpha and beta.
Popa
Claudia
C
Epithelial Pathobiology Group, Cancer Biology Program, Centre for Immunology and Cancer Research, University of Queensland, Building 1, R Wing, Level 4, Princess Alexandra Hospital, Brisbane, Queensland, Australia.
Dahler
Alison L
AL
Serewko-Auret
Magdalena M
MM
Wong
Chung F
CF
Smith
Louise
L
Barnes
Liam M
LM
Strutton
Geoff M
GM
Saunders
Nicholas A
NA
D015153:Blotting, Western; D002454:Cell Differentiation / Q000502:physiology; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D024202:Electrophoretic Mobility Shift Assay; D006801:Humans; D007150:Immunohistochemistry; D015603:Keratinocytes / Q000166:cytology / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D050656:Transcription Factor AP-2; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism
D004268:DNA-Binding Proteins; D012333:RNA, Messenger; C493677:TFAP2B protein, human; D050656:Transcription Factor AP-2; D014157:Transcription Factors