Identification and functional characterization of two new transcriptional variants of the human p63 gene

Abstract

p63 belongs to a family of transcription factors, which, while demonstrating striking conservation of functional domains, regulate distinct biological functions. Its principal role is in the regulation of epithelial commitment, differentiation and maintenance programs, during embryogenesis and in adult tissues. The p63 gene has a complex transcriptional pattern, producing two subclasses of N-terminal isoforms (TA and ΔN) which are alternatively spliced at the C-terminus. Here, we report the identification of two new C-terminus p63 variants, we named p63 δ and ε, that increase from 6 to 10 the number of the p63 isoforms. Expression analysis of all p63 variants demonstrates a tissue/cell-type-specific nature of p63 alternative transcript expression, probably related to their different cellular functions. We demonstrate that the new p63 variants as ΔN isoforms are active as transcription factors as they have nuclear localization and can modulate the expression of p63 target genes. Moreover, we report that, like ΔNp63α, ΔNp63δ and ε sustain cellular proliferation and that their expression decreases during keratinocyte differentiation, suggesting their involvement in this process. Taken together, our results demonstrate the existence of novel p63 proteins whose expression should be considered in future studies on the roles of p63 in the regulation of cellular functions.

ΔNp63α regulates keratinocyte proliferation by controlling PTEN expression and localization

“…Consistent with earlier reports, we demonstrated that DNp63a is the predominant isoform in both HaCaT and A431 cell lines. 15,16 A faint band corresponding to TAp63g was detected upon immunoblot analysis using a TA-specific antibody (Supplementary Figure S1). To determine the effect of DNp63a on PTEN, we knocked down p63 in both mutant p53 (A431 and HaCaT, Figure 1a) and wild-type p53 (primary human keratinocytes, Figure 1b) backgrounds.…”

p63 is a suppressor of tumorigenesis and metastasis interacting with mutant p53

“…In silico analysis predicted the d isoform (skipping exon [12][13] and the e isoform (premature termination in intron 10 retaining the 5 0 -portion of intron 10 with a stop codon p63 is the most recently discovered but the most ancient member of the p53 family [8][9][10][11][12][13][14][15]28 ( Figure 1). As indicated above, p63 is transcribed from two promoters, giving rise to proteins that may (TAp63 isoforms) or may not (DNp63 isoforms) contain the TA, 1 and alternative splicing at the 3 0 -end produces additional proteins (a-e isoforms), 29 although there is no in vivo evidence for two latter isoforms. Whereas the TAp63 proteins are capable of transactivation, the DNp63 forms can also act in a dominant-negative fashion to counteract the transcriptional activity of the TAp63 isoforms and p53.…”

Regulation of skin aging and heart development by TAp63

“…1 By encoding two different N-termini (TA and DN) and multiple C-termini by alternative splicing, the TP63 gene generates multiple-protein isoforms. 2,3 All p63 isoforms contain identical DNA binding and oligomerization domains and are able to transactivate p53-responsive and specific target genes. 4 Moreover, p53 gene members functions sometimes in an interdependent way.…”