Limits...
p53 acts as a co-repressor to regulate keratin 14 expression during epidermal cell differentiation.

Cai BH, Hsu PC, Hsin IL, Chao CF, Lu MH, Lin HC, Chiou SH, Tao PL, Chen JY - PLoS ONE (2012)

Bottom Line: 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.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.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology and Anatomy, National Defense Medical Center, Taipei, Taiwan, Republic of China.

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.

Show MeSH

Related in: MedlinePlus

p53 and p63 are involved in the regulation of epidermal differentiation.p63 is used as a stem cell maker because it is persistently expressed in the basal layer of the epidermis and is inhibited during epidermal differentiation. Because p63 only expresses a dominant negative isoform, ΔNp63α, within the epidermal cell basal layer, p53 activity is up-regulated after p63 withdrawn as a result of epidermal differentiation, and p53 downstream targets such as p21 become induced. K14 is a basal layer-expressed keratin subtype and can be up-regulated by p63. During epidermal differentiation, K14 expression is down-regulated by the loss of p63 and is repressed by the activity of p53.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC3404013&req=5

pone-0041742-g009: p53 and p63 are involved in the regulation of epidermal differentiation.p63 is used as a stem cell maker because it is persistently expressed in the basal layer of the epidermis and is inhibited during epidermal differentiation. Because p63 only expresses a dominant negative isoform, ΔNp63α, within the epidermal cell basal layer, p53 activity is up-regulated after p63 withdrawn as a result of epidermal differentiation, and p53 downstream targets such as p21 become induced. K14 is a basal layer-expressed keratin subtype and can be up-regulated by p63. During epidermal differentiation, K14 expression is down-regulated by the loss of p63 and is repressed by the activity of p53.

Mentions: p63 is a key regulator of epidermal development and differentiation [6], [7], [33], [34], but the role of p53 in epidermal differentiation remains unclear. One study suggests that functional p53 over-expression in HaCat cells promotes differentiation faster than control cells [30]. Another study suggests that the HPV E6 oncoprotein is able to degrade p53 and inhibit the differentiation of human keratinocytes [35]. The other study shows that ultraviolet (UV) light induces mouse epidermis differentiation, but this effect is lost in p53 epidermal tissue [36]. Our results suggest that p53 activation promotes the expression of p21 and the repression of K14 during epidermal differentiation. In addition, the down-regulation of p63 led to a loss of activation function on K14 (Fig. 9). These results suggest a mechanism whereby the replacement of the basal layer expressing K14 with the supra-basal layer containing keratin during the epidermal differentiation is cooperatively mediated by both p53 and p63. Other examples of p53 and p63 cooperation in the epidermis include Notch1 and Hsp70. Notch 1 is primarily distributed in the supra-basal layer of the epidermis [37]. ΔNp63α suppresses Notch1 activity in keratinocytes within the basal layer [38], and p53 can enhance Notch 1 expression after keratinocyte differentiation [36]. Hsp70 is most highly concentrated in the basal layer of the epidermis. [39]. ΔNp63α enhances Hsp70 expression [40], and p53 represses Hsp70 expression. [41]. Based on our data and previous studies, we predict that many keratinocyte-specific markers that are regulated by p53 and p63 during epidermal differentiation will be identified.


p53 acts as a co-repressor to regulate keratin 14 expression during epidermal cell differentiation.

Cai BH, Hsu PC, Hsin IL, Chao CF, Lu MH, Lin HC, Chiou SH, Tao PL, Chen JY - PLoS ONE (2012)

p53 and p63 are involved in the regulation of epidermal differentiation.p63 is used as a stem cell maker because it is persistently expressed in the basal layer of the epidermis and is inhibited during epidermal differentiation. Because p63 only expresses a dominant negative isoform, ΔNp63α, within the epidermal cell basal layer, p53 activity is up-regulated after p63 withdrawn as a result of epidermal differentiation, and p53 downstream targets such as p21 become induced. K14 is a basal layer-expressed keratin subtype and can be up-regulated by p63. During epidermal differentiation, K14 expression is down-regulated by the loss of p63 and is repressed by the activity of p53.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3404013&req=5

pone-0041742-g009: p53 and p63 are involved in the regulation of epidermal differentiation.p63 is used as a stem cell maker because it is persistently expressed in the basal layer of the epidermis and is inhibited during epidermal differentiation. Because p63 only expresses a dominant negative isoform, ΔNp63α, within the epidermal cell basal layer, p53 activity is up-regulated after p63 withdrawn as a result of epidermal differentiation, and p53 downstream targets such as p21 become induced. K14 is a basal layer-expressed keratin subtype and can be up-regulated by p63. During epidermal differentiation, K14 expression is down-regulated by the loss of p63 and is repressed by the activity of p53.
Mentions: p63 is a key regulator of epidermal development and differentiation [6], [7], [33], [34], but the role of p53 in epidermal differentiation remains unclear. One study suggests that functional p53 over-expression in HaCat cells promotes differentiation faster than control cells [30]. Another study suggests that the HPV E6 oncoprotein is able to degrade p53 and inhibit the differentiation of human keratinocytes [35]. The other study shows that ultraviolet (UV) light induces mouse epidermis differentiation, but this effect is lost in p53 epidermal tissue [36]. Our results suggest that p53 activation promotes the expression of p21 and the repression of K14 during epidermal differentiation. In addition, the down-regulation of p63 led to a loss of activation function on K14 (Fig. 9). These results suggest a mechanism whereby the replacement of the basal layer expressing K14 with the supra-basal layer containing keratin during the epidermal differentiation is cooperatively mediated by both p53 and p63. Other examples of p53 and p63 cooperation in the epidermis include Notch1 and Hsp70. Notch 1 is primarily distributed in the supra-basal layer of the epidermis [37]. ΔNp63α suppresses Notch1 activity in keratinocytes within the basal layer [38], and p53 can enhance Notch 1 expression after keratinocyte differentiation [36]. Hsp70 is most highly concentrated in the basal layer of the epidermis. [39]. ΔNp63α enhances Hsp70 expression [40], and p53 represses Hsp70 expression. [41]. Based on our data and previous studies, we predict that many keratinocyte-specific markers that are regulated by p53 and p63 during epidermal differentiation will be identified.

Bottom Line: 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.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.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology and Anatomy, National Defense Medical Center, Taipei, Taiwan, Republic of China.

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.

Show MeSH
Related in: MedlinePlus