title: Functional role of CCCTC binding factor (CTCF) in stress-induced apoptosis.
abstract: CTCF, a nuclear transcriptional factor, is a multifunctional protein and involves regulation of growth factor- and cytokine-induced cell proliferation/differentiation. In the present study, we investigated the role of CTCF in protecting stress-induced apoptosis in various human cell types. We found that UV irradiation and hyper-osmotic stress induced human corneal epithelial (HCE) and hematopoietic myeloid cell apoptosis detected by significantly increased caspase 3 activity and decreased cell viability. The stress-induced apoptotic response in these cells requires down-regulation of CTCF at both mRNA and protein levels, suggesting that CTCF may play an important role in downstream events of stress-induced signaling pathways. Inhibition of NFkappaB activity prevented stress-induced down-regulation of CTCF and increased cell viability against stress-induced apoptosis. The anti-apoptotic effect of CTCF was further studied by manipulating CTCF activities in HCE and hematopoietic cells. Transient transfection of cDNAs encoding full-length human CTCF markedly suppressed stress-induced apoptosis in these cells. In contrast, knocking down of CTCF mRNA using siRNA specific to CTCF significantly promoted stress-induced apoptosis. Thus, our results reveal that CTCF is a down stream target of stress-induced signaling cascades and it plays a significant anti-apoptotic role in regulation of stress-induced cellular responses in HCE and hematopoietic myeloid cells.
authors.affiliation: Department of Medicine, HMC, David Geffen School of Medicine, University of California-Los Angeles, Torrance, CA 90502, USA.
authors.forename: Tie
authors.initials: T
authors.lastname: Li
authors.forename: Luo
authors.initials: L
authors.lastname: Lu
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D000076246:CCCTC-Binding Factor; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D019573:Epithelium, Corneal / Q000166:cytology; D006412:Hematopoietic Stem Cells / Q000166:cytology / Q000502:physiology; D006801:Humans; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000378:metabolism; D018384:Oxidative Stress; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology; D014466:Ultraviolet Rays
chemical_list: D000076246:CCCTC-Binding Factor; C000619697:CTCF protein, human; D004268:DNA-Binding Proteins; D016328:NF-kappa B; D034741:RNA, Small Interfering; D012097:Repressor Proteins