p63 maintains keratinocyte proliferative capacity through regulation of Skp2–p130 levels

Abstract

p63 is a master regulator of proliferation and differentiation in stratifying epithelia, and its expression is frequently altered in carcinogenesis. However, its role in maintaining proliferative capacity remains unclear. Here, we demonstrate that hypoproliferation and loss of differentiation in organotypic raft cultures of primary neonatal human foreskin keratinocytes (HFKs) depleted of the α and β isoforms of p63 result from p53–p21-mediated accumulation of retinoblastoma (Rb) family member p130. Hypoproliferation in p63-depleted HFKs can be rescued by depletion of p53, p21CIP1 or p130. Furthermore, we identified the gene encoding S-phase kinase-associated protein 2 (Skp2), the recognition component of the SCFSkp2 E3 ubiquitin ligase, as a novel target of p63, potentially influencing p130 levels. Expression of Skp2 is maintained by p63 binding to a site in intron 2 and mRNA levels are downregulated in p63-depleted cells. Hypoproliferation in p63-depleted cells can be restored by re-expression of Skp2. Taken together, these results indicate that p63 plays a multifaceted role in maintaining proliferation in the mature regenerating epidermis, in addition to being required for differentiation.

Modulation of basal cell fate during productive and transforming HPV-16 infection is mediated by progressive E6-driven depletion of Notch

“…The ablation of p53 resulted in a marginal increase in mini‐chromosome maintenance‐7 (MCM7) levels (Figure C), which might be expected given the increased NIKS cell growth seen following p53 ablation (Figure C, lower panel and supplementary material, Figure S5). Previous studies suggested that expression of the p53 homologue p63 maintains the proliferative capacity of keratinocytes . Consistent with this, the ablation of p63 in NIKS keratinocytes led to a dramatic reduction of their growth rate (supplementary material, Figure S5).…”

Various peroxisome proliferator‐activated receptor (PPAR)‐γ agonists differently induce differentiation of cultured human keratinocytes

“…This discrepancy is probably due to more potent structure-specific PPAR-independent activity ('off-target' effects) of ciglitazone and troglitazone than rosiglitazone and pioglitazone (15). Previous studies suggested that such strong off-target effects can reduce cornification marker expression in keratinocytes during later stages of differentiation via p63-mediated sustained p21 expression (16)(17)(18)(19)(20)(21).…”

Human papillomavirus 16E6 and NFX1-123 potentiate notch signaling and differentiation without activating cellular arrest

“…Values graphed are the mean fold-change in each sample compared to control, and error bars graphed represent the standard deviation for each sample (n=3). Primer sequences for NFX1-123, p21 Waf1/CIP1 and 36B4 were described previously (McDade, Patel et al, 2011; Katzenellenbogen, Egelkrout et al, 2007). Amplification was carried out as previously published (Katzenellenbogen, Egelkrout et al, 2007) using Power Sybr Green Master Mix (Life Technologies, Foster City, CA.…”