Dataset Information

Protein kinase C (PKC) delta suppresses keratinocyte proliferation by increasing p21(Cip1) level by a KLF4 transcription factor-dependent mechanism.

ABSTRACT: PKC? increases keratinocyte differentiation and suppresses keratinocyte proliferation and survival. However, the mechanism of proliferation suppression is not well understood. The present studies show that PKC? overexpression increases p21(Cip1) mRNA and protein level and promoter activity and that treatment with dominant-negative PKC?, PKC?-siRNA, or rottlerin inhibits promoter activation. Analysis of the p21(Cip1) promoter upstream regulatory region reveals three DNA segments that mediate PKC?-dependent promoter activation. The PKC? response element most proximal to the transcription start site encodes six GC-rich DNA elements. Mutation of these sites results in a loss of PKC?-dependent promoter activation. Gel mobility supershift and chromatin immunoprecipitation reveal that these DNA elements bind the Kruppel-like transcription factor KLF4. PKC? increases KLF4 mRNA and protein level and KLF4 binding to the GC-rich elements in the p21(Cip1) proximal promoter. In addition, KLF4-siRNA inhibits PKC?-dependent p21(Cip1) promoter activity. PKC? increases KLF4 expression leading to enhanced KLF4 interaction with the GC-rich elements in the p21(Cip1) promoter to activate transcription.

SUBMITTER: Chew YC

PROVIDER: S-EPMC3190685 | biostudies-literature | 2011 Aug

REPOSITORIES: biostudies-literature

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Protein kinase C (PKC) delta suppresses keratinocyte proliferation by increasing p21(Cip1) level by a KLF4 transcription factor-dependent mechanism.

Chew Yap Ching YC Adhikary Gautam G Wilson Gerald M GM Reece E Albert EA Eckert Richard L RL

The Journal of biological chemistry 20110607 33

PKCδ increases keratinocyte differentiation and suppresses keratinocyte proliferation and survival. However, the mechanism of proliferation suppression is not well understood. The present studies show that PKCδ overexpression increases p21(Cip1) mRNA and protein level and promoter activity and that treatment with dominant-negative PKCδ, PKCδ-siRNA, or rottlerin inhibits promoter activation. Analysis of the p21(Cip1) promoter upstream regulatory region reveals three DNA segments that mediate PKCδ ...[more]

PMID: 21652709

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Project description:The Ets family of transcription factors control a myriad of cellular processes and contribute to the underlying genetic loss of cellular homeostasis resulting in cancer. PDEF (prostate-derived Ets factor) has been under investigation for its role in tumor development and progression. However, the role of PDEF in cancer development has been controversial. Some reports link PDEF to tumor promoter, and others show tumor-suppressing functions in various systems under different conditions. So far, there has been no conclusive evidence from in vivo experiments to prove the role of PDEF. We have used both in vitro and in vivo systems to provide a conclusive role of PDEF in the progression process. PDEF-expressing cells block the cell growth rate, and this retardation was reversible when PDEF expression was silenced with PDEF-specific small interfering RNA. When these PDEF-expressing cells were orthotopically implanted into the mouse mammary gland, tumor incidence and growth rate were significantly retarded. Cell cycle analysis revealed that PDEF expression partially blocked cell cycle progression at G(1)/S without an effect on apoptosis. PDEF overexpression resulted in an increase in p21/CIP1 at both the mRNA and protein levels, resulting in decreased Cdk2 activity. Promoter deletion analysis, electrophoresis mobility shift assays, and chromatin immunoprecipitation studies identified the functional Ets DNA binding site at -2118 bp of the p21/CIP1 gene promoter. This site is capable of binding and responding to PDEF. Furthermore, we silenced p21/CIP1 expression in PDEF-overexpressing cells by small interfering RNA. p21-silenced PDEF cells exhibited significantly increased cell growth in vitro and in vivo, demonstrating the p21 regulation by PDEF as a key player. These experiments identified PDEF as a new transcription factor that directly regulates p21/CIP1 expression under non-stressed conditions. This study conclusively proves that PDEF is a breast tumor suppressor for the first time using both in vitro and in vivo systems. PDEF can be further developed as a target for designing therapeutic intervention of breast cancer.

Dataset Information

Protein kinase C (PKC) delta suppresses keratinocyte proliferation by increasing p21(Cip1) level by a KLF4 transcription factor-dependent mechanism.

Publications

Protein kinase C (PKC) delta suppresses keratinocyte proliferation by increasing p21(Cip1) level by a KLF4 transcription factor-dependent mechanism.

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