NF-κB Subtypes Regulate CCCTC Binding Factor Affecting Corneal Epithelial Cell Fate

Abstract

CCCTC binding factor (CTCF) controls DNA imprinting, insulates important gene expression, and mediates growth factor-and stress-induced cell fate. However, regulatory mechanisms involved in intracellular CTCF activity are largely unknown. In this study, we show that epidermal growth factor (EGF)-induced increase and UV stress-induced decrease in CTCF activities mediate human corneal epithelial cell proliferation and apoptosis, respectively. CTCF is regulated by activation of different NF-B subtypes via stimulation by EGF and UV stress. EGF-induced formation of a p65/p50 heterodimer activated CTCF transcription to promote cellular proliferation. This was accomplished by the heterodimer binding to a B site in the promoter region of CTCF gene. In contrast, UV stress induced formation of a p50/p50 homodimer, which suppressed CTCF expression leading to apoptosis. Thus, CTCF by itself plays a central role in mediating the dichotomous effects of growth factor-and stress-stimulated NF-B activation on cell survival and death. These results suggest that CTCF is a downstream component of the NF-B pathway involved in the core transcriptional network of cell fate.

Epidermal Growth Factor (EGF)-induced Corneal Epithelial Wound Healing through Nuclear Factor κB Subtype-regulated CCCTC Binding Factor (CTCF) Activation

“…Recent studies indicate that CTCF is involved in * This work was supported, in whole or in part, by National Institutes of Grants the regulation of cell migration in cancer cell proliferation, tumor suppression, and apoptosis (29 -31). In corneal epithelial cells, EGF-induced activation of the NF-B pathway regulates cell fate in a subtype-specific fashion through interactions with CTCF that function as a downstream component in the core transcriptional network (14,32). We found that, in corneal epithelial cells, CTCF is a targeted gene of the growth factor-induced pathways, including the Erk, AKT, and NF-B signaling cascades.…”

“…As demonstrated in human corneal epithelial cells, EGF elicits complex responses at early times by inducing specific cellular signaling pathways that transfer the signals to the nucleus and activate the transcription factor at later times (3,14,15,33,38). In previous studies, we found that EGF-induced formations of the NFB p65/p50 heterodimer and p50/50 homodimer activate CTCF transcription by binding to a B site located in the promoter region of the CTCF gene and that an increase in CTCF activity in corneal epithelial cells promotes cell motility and migration (14,17). These results indicate that NFB subtypes interact directly with the CTCF gene in the promoter region.…”

“…Suppression of NF-B p50 Overexpression-induced Acceleration of Wound Healing by Knocking Down CTCF-We reported that expression of CTCF is regulated by the NF-B subtype p50 in human corneal epithelial cells (14). In this study, NF-B p50-specific cDNA and shRNA were used to overexpress and knock down the p50 in these cells, respectively.…”

“…The effect of EGF on suppressing Pax6 expression is through activation of CTCF, 2 an epigenetic CCCTC binding factor and zinc finger protein (16). In corneal epithelial cells, we found that EGF induces NF-B subtype-specific signaling cascades to regulate CTCF activity and to promote cell proliferation (14). Our recent study demonstrates that CTCF is required for the EGF-induced alteration of focal adhesion and increases in cell motility and migration (17).…”

“…We found that, in corneal epithelial cells, CTCF is a targeted gene of the growth factor-induced pathways, including the Erk, AKT, and NF-B signaling cascades. Activation of these signaling pathways by stimulation of EGF, insulin, and other stresses subsequently regulates the expression levels of CTCF to determine the corneal epithelial fate in the process of wound healing (12)(13)(14)32).…”