deltaNp63alpha functions as both a positive and a negative transcriptional regulator and blocks in vitro differentiation of murine keratinocytes.
deltaNp63 is overexpressed in squamous carcinomas where it is associated with proliferation and is believed to enhance cell growth by blocking p53-mediated transactivation. In normal epithelium, deltaNp63alpha protein expression is abundant in basal cells and decreases with differentiation. To explore the biological consequences of deltaNp63alpha overexpression in relation to squamous carcinogenesis, we evaluated its effect on normal squamous differentiation and p53 transactivation function in keratinocytes. Forced overexpression of deltaNp63alpha in primary murine keratinocytes in vitro inhibits morphological differentiation induced by elevated extracellular [Ca(2+)], abrogates Ca(2)(+)-induced growth arrest, and blocks expression of maturation-specific proteins keratin 10 and filaggrin. This suggests that deltaNp63 overexpression in squamous carcinomas may serve to maintain the basal cell phenotype and promote cell survival. deltaNp63alpha blocks transactivation of p53 responsive reporter constructs mediated by endogenous or exogenous p53 at 17 h postinfection, as expected. However, at 41 h, when p53-mediated transactivation is diminished, deltaNp63alpha enhances transactivation of these reporter constructs by 2.2-12-fold over control. Maximal deltaNp63alpha-induced transactivation requires intact p53 responsive elements, but is independent of cellular p53 status. This positive transcriptional function of deltaNp63alpha appears to be cell-type specific, as it is not observed in primary dermal fibroblasts or Saos-2 cells. These findings support deltaNp63alpha as a master regulator of keratinocyte differentiation, and suggest a novel function of this protein in the maintenance of epithelial homeostasis.
King
Kathryn E
KE
Center for Biologics Evaluation and Research, FDA, Bethesda, MD 20892, USA.
Ponnamperuma
Roshini M
RM
Yamashita
Toshiharu
T
Tokino
Takashi
T
Lee
Lela A
LA
Young
Marian F
MF
Weinberg
Wendy C
WC
D000256:Adenoviridae / Q000235:genetics; D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D000818:Animals; D001665:Binding Sites; D001859:Bone Neoplasms / Q000235:genetics / Q000473:pathology; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology; D002454:Cell Differentiation / Q000502:physiology*; D002478:Cells, Cultured; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism*; D005347:Fibroblasts / Q000166:cytology / Q000187:drug effects; D000091344:Filaggrin Proteins; D017930:Genes, Reporter; D016147:Genes, Tumor Suppressor; D006801:Humans; D015603:Keratinocytes / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D009928:Organ Specificity; D012516:Osteosarcoma / Q000235:genetics / Q000473:pathology; D010750:Phosphoproteins; D020033:Protein Isoforms; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D015534:Trans-Activators; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism; D025521:Tumor Suppressor Proteins
D000590:Amino Acid Chloromethyl Ketones; D015853:Cysteine Proteinase Inhibitors; D004268:DNA-Binding Proteins; C000717249:FLG protein, human; D000091344:Filaggrin Proteins; D010750:Phosphoproteins; D020033:Protein Isoforms; D011994:Recombinant Proteins; C115051:TP63 protein, human; D015534:Trans-Activators; D014157:Transcription Factors; C486419:Trp63 protein, mouse; D016159:Tumor Suppressor Protein p53; D025521:Tumor Suppressor Proteins; C096713:benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone; D002118:Calcium