p53 Acts as a Co-Repressor to Regulate Keratin 14 Expression during Epidermal Cell Differentiation

Abstract

During epidermal cell differentiation, keratin 14 (K14) expression is down-regulated, p53 expression varies, and the expression of the p53 target genes, p21 and 14-3-3σ, increases. These trends suggest that the relative transcriptional activity of p53 is increased during epidermal cell differentiation. To determine the relationship between K14 and p53, we constructed K14 promoters of various sizes and found that wild-type p53 could repress the promoter activity of all of the K14 promoter constructs in H1299 cells. K14-p160 contains an SP1 binding site mutation that prevents p53 from repressing K14 expression. Using a DNA affinity precipitation assay, we confirmed that p53 forms a complex with SP1 at the SP1 binding site between nucleotides -48 and -43 on the K14 promoter. Thus, our data indicate that p53 acts as a co-repressor to down-regulate K14 expression by binding to SP1. Next, we used a 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced epidermal cell differentiation model to examine the inhibition of K14 expression caused by increased p53 activity. Human ovarian teratocarcinoma C9 cells were treated with TPA to induce differentiation. Over-expression of the dominant negative p53 mutant ΔTAp53, which inhibits p53 activity, prevented the TPA-induced K14 down-regulation in C9 cells. Furthermore, treatment of normal primary human foreskin keratinocytes (PHFK) with the p53 inhibitor pifithrin-α (PFT-α) showed that the inhibition of p53 activity relieves K14 repression during epidermal cell differentiation. Finally, we found that TPA induces the phosphorylation of p53 at residue 378, which enhances the affinity of p53 to bind to Sp1 and repress K14 expression.

FoxO1 enhances differentiation and apoptosis in human primary keratinocytes

“…Based on indirect translational evidence, Melnik predicted that isotretinoin may increase nuclear levels of p53 and FoxO1, but direct evidence has not been provided. p53 is a tumor suppressor gene that regulates cell proliferation, but its expression level is dependent on the cell line in calcium‐induced differentiation models of human keratinocytes . HPKs were treated with different doses of isotretinoin for 24 hour.…”

A/T gap tolerance in the core sequence and flanking sequence requirements of non-canonical p53 response elements

“…5A). We previous found that keratin 14 promoter could be activated by p63 but repressed by p53 (10,48). p53 repressed K14 promoter through indirect binding to SP1 transcription factor (48), and it had been reported that SV40 promoter have several SP1 binding sites (49).…”

“…We previous found that keratin 14 promoter could be activated by p63 but repressed by p53 (10,48). p53 repressed K14 promoter through indirect binding to SP1 transcription factor (48), and it had been reported that SV40 promoter have several SP1 binding sites (49). p53 interacts with SP1 through its C-terminal domain but not DNA binding domain which interacts with SV40 Large T antigen (50,51), and this maybe the reason why p53 still could repress SV40 T antigens expression in 293T cells.…”

A Synthetic Interaction Screen Identifies Factors Selectively Required for Proliferation and TERT Transcription in p53-Deficient Human Cancer Cells

“…In p53+ HCT116 cells there was increased binding of SP1 (Figure S15C) and, most notably, there was substantial binding of p53 to the TERT promoter (Figure S15D). Interestingly, a number of previous studies have reported physical and functional interactions between SP1 and p53 (see, for example, [37]–[41]). Our ChIP results reveal substantial differences between the composition of proteins associated with the TERT promoter in p53+ and p53− HCT116 cells, which may be related to the differential requirement for ETV1.…”