Delta Np63 alpha functions as both a positive and a negative transcriptional regulator and blocks in vitro differentiation of murine keratinocytes
ABSTRACT 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.
SourceAvailable from: Kotaro Sugimoto[Show abstract] [Hide abstract]
ABSTRACT: In the epidermis, tight junction (TJ) structure is specifically located in the stratum granulosum, where the expression of ΔNp63, a p53 family transcription factor, is attenuated. Since the relationship between ΔNp63 and barrier function has not been fully uncovered, we assessed expression profiles of TJ proteins in skin tissues and cultured keratinocytes. The results showed that expression of ΔNp63 and that of claudin-4 were inversely correlated in healthy human epidermis. In vitro studies using HaCaT keratinocytes revealed functional relevance of ΔNp63 and claudin-4. Curiously, Toll-like receptor (TLR) -3 ligand, which is known to be liberated from damaged cells, suppressed ΔNp63 expression and concomitantly upregulated claudin-4 expression in primary keratinocytes. More interestingly, a broad expression pattern of claudin-4 was found in the epidermis of atopic dermatitis (AD), a barrier defect disorder, which contains ΔNp63-lacking keratinocytes as we reported previously. Therefore, upregulation of claudin-4 expression regulated by ΔNp63 might be associated with complementary or repair responses of damaged keratinocytes with AD.Biochemical and Biophysical Research Communications 11/2014; 455(3-4). DOI:10.1016/j.bbrc.2014.10.148 · 2.28 Impact Factor
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ABSTRACT: p63 is a crucial regulator of epidermal development, but its transcriptional control has remained elusive. Here, we report the identification of a long-range enhancer (p63LRE) that is composed of two evolutionary conserved modules (C38 and C40), acting in concert to control tissue- and layer-specific expression of the p63 gene. Both modules are in an open and active chromatin state in human and mouse keratinocytes and in embryonic epidermis, and are strongly bound by p63. p63LRE activity is dependent on p63 expression in embryonic skin, and also in the commitment of human induced pluripotent stem cells toward an epithelial cell fate. A search for other transcription factors involved in p63LRE regulation revealed that the CAAT enhancer binding proteins Cebpa and Cebpb and the POU domain-containing protein Pou3f1 repress p63 expression during keratinocyte differentiation by binding the p63LRE enhancer. Collectively, our data indicate that p63LRE is composed of additive and partly redundant enhancer modules that act to direct robust p63 expression selectively in the basal layer of the epidermis. © The Author(s) 2015. Published by Oxford University Press on behalf of Nucleic Acids Research.Nucleic Acids Research 01/2015; DOI:10.1093/nar/gku1396 · 8.81 Impact Factor