Induction of Disease-associated Keratin 16 Gene Expression by Epidermal Growth Factor Is Regulated through Cooperation of Transcription Factors Sp1 and c-Jun

Abstract

Overexpression of keratin 16 has been observed in keratinocytes in those skin diseases characterized by hyperproliferation such as psoriasis. Therefore, keratin 16 is usually referred to as a disease-associated keratin. In the present study, we found that epidermal growth factor (EGF) increased the expression of keratin 16 mRNA and protein synthesis in a time-dependent manner in HaCaT cells. Reporter assays revealed that the EGF response region was in the range of ؊162 to ؊114 bp. Disruption of the Sp1 site (؊127 to ؊122 bp) and the AP1 site (؊148 to ؊142 bp) of the keratin 16 promoter by site-directed mutagenesis significantly inhibited keratin 16 promoter activity induced by EGF. Furthermore, keratin 16 gene expression induced by Ras activation was also regulated in the same manner as the EGF response. By using the DNA affinity precipitation assay in HaCaT and SL2 cells, Sp1 directly interacted with the Sp1 site of the promoter, and c-Jun and c-Fos precipitated with the Sp1 oligonucleotide was attributable to the interaction between the Sp1 and AP1 proteins. Moreover, cotransfection assays revealed that Sp1 acted synergistically with c-Jun to activate keratin 16. The coactivators p300/CBP could collaborate with Sp1 and c-Jun in the activation of keratin 16 promoter, and EGF-induced promoter activation was blocked by the viral oncoprotein E1A. Taken together, these results suggest that Sp1 and AP1 sites in the essential promoter region are critical for EGF response, and Sp1 showed a functional cooperation with c-Jun and coactivators p300/ CBP in driving the transcriptional regulation of EGFinduced keratin 16 gene expression.

Direct interaction of C/EBPδ and Sp1 at the GC-enriched promoter region synergizes the IL-10 gene transcription in mouse macrophage

“…Since both the C/EBP and Sp1 binding sites on the gene promoter are required for the LPS-induced gene expression of IL-10 in mouse macrophage cells [45], our present results indicate that C/EBPd acts on both the C/EBP and Sp1 binding sites on the gene promoter of IL-10 to activate the gene transcription. A transcription factor acting through its own response element and also through its interaction with Sp1, followed by the binding of the latter formed complex to the Sp1 response element on a gene promoter was also observed in our previous study examining the functional role of c-Jun and Sp1 in epidermal growth factor (EGF)-induced gene activation of disease-associated keratin 16 in human keratinocytes [48]. In the study of keratin 16 gene expression, we found that both AP1 and Sp1 binding elements on the gene promoter are required for the EGF-induced gene expression.…”

Activation of Extracellular Signal-Regulated Kinase Signaling by Epidermal Growth Factor Mediates c-Jun Activation and p300 Recruitment in Keratin 16 Gene Expression

“…We have provided a proposed model for the transcriptional regulation of the keratin 16 gene, indicating that Sp1 recruits c-Jun to the promoter through the binding of Sp1 to the Sp1 site and coactivators p300/CBP interact with Sp1 and AP1 proteins and participate in the transcriptional regulation for EGF induction of keratin 16 gene expression in keratinocytes (Wang and Chang, 2003). The aim of the present work is to further investigate the signaling pathway and the regulatory mechanism of these nuclear factors involved in the transcriptional control of keratin 16 upon EGF treatment.…”

Wound Repair Studies Reveal New Insights to Psoriasis

“…Keratinocytes in wound sites and psoriatic lesions are also similarly differentiated; both express keratin 6 (K6), keratin 16 (K16) and keratin 17 (K17) instead of the standard keratin 1 (K1) and keratin 10 (K10) expressed by normal differentiating suprabasal keratinocytes (de Jong et al, 1991;Mommers et al, 2000;Wang & Chang, 2003). This suggests that transcriptional regulation responsible for both wound healing and psoriasis are similar.…”