Reciprocal regulation of p63 by C/EBP delta in human keratinocytes.
BACKGROUND
Genetic experiments have clarified that p63 is a key transcription factor governing the establishment and maintenance of multilayered epithelia. Key to our understanding of p63 strategy is the identification of target genes. We perfomed an RNAi screening in keratinocytes for p63, followed by profiling analysis.


RESULTS
C/EBPdelta, member of a family with known roles in differentiation pathways, emerged as a gene repressed by p63. We validated C/EBPdelta as a primary target of DeltaNp63alpha by RT-PCR and ChIP location analysis in HaCaT and primary cells. C/EBPdelta is differentially expressed in stratification of human skin and it is up-regulated upon differentiation of HaCaT and primary keratinocytes. It is bound to and activates the DeltaNp63 promoter. Overexpression of C/EBPdelta leads to alteration in the normal profile of p63 isoforms, with the emergence of DeltaNp63beta and gamma, and of the TA isoforms, with different kinetics. In addition, there are changes in the expression of most p63 targets. Inactivation of C/EBPdelta leads to gene expression modifications, in part due to the concomitant repression of DeltaNp63alpha. Finally, C/EBPdelta is found on the p63 targets in vivo by ChIP analysis, indicating that coregulation is direct.


CONCLUSIONS
Our data highlight a coherent cross-talk between these two transcription factors in keratinocytes and a large sharing of common transcriptional targets.
Borrelli
Serena
S
Dipartimento di Scienze Biomolecolari e Biotecnologie, U, di Milano, Via Celoria 26, 20133 Milano, Italy. serena.borrelli@unimi.it
Testoni
Barbara
B
Callari
Maurizio
M
Alotto
Daniela
D
Castagnoli
Carlotta
C
Romano
Rose-Anne
RA
Sinha
Satrajit
S
Viganò
Alessandra M
AM
Mantovani
Roberto
R
D051743:CCAAT-Enhancer-Binding Protein-delta / Q000235:genetics / Q000378:metabolism*; D002454:Cell Differentiation / Q000502:physiology*; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D005260:Female; D017353:Gene Deletion; D020869:Gene Expression Profiling; D006801:Humans; D015603:Keratinocytes / Q000166:cytology / Q000378:metabolism*; D020411:Oligonucleotide Array Sequence Analysis; D011401:Promoter Regions, Genetic / Q000502:physiology*; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012867:Skin / Q000166:cytology / Q000378:metabolism*; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000378:metabolism*
D004268:DNA-Binding Proteins; D020033:Protein Isoforms; C115051:TP63 protein, human; D015534:Trans-Activators; D014157:Transcription Factors; D025521:Tumor Suppressor Proteins; D051743:CCAAT-Enhancer-Binding Protein-delta