title: Transcriptional repression of Kruppel like factor-2 by the adaptor protein p66shc.
abstract: The adaptor protein p66shc promotes cellular oxidative stress and apoptosis. Here, we demonstrate a novel mechanistic relationship between p66shc and the kruppel like factor-2 (KLF2) transcription factor and show that this relationship has biological relevance to p66shc-regulated cellular oxidant level, as well as KLF2-induced target gene expression. Genetic knockout of p66shc in mouse embryonic fibroblasts (MEFs) stimulates activity of the core KLF2 promoter and increases KLF2 mRNA and protein expression. Similarly, shRNA-induced knockdown of p66shc increases KLF2-promoter activity in HeLa cells. The increase in KLF2-promoter activity in p66shc-knockout MEFs is dependent on a myocyte enhancing factor-2A (MEF2A)-binding sequence in the core KLF2 promoter. Short-hairpin RNA-induced knockdown of p66shc in endothelial cells also stimulates KLF2 mRNA and protein expression, as well as expression of the endothelial KLF2 target gene thrombomodulin. MEF2A protein and mRNA are more abundant in p66shc-knockout MEFs, resulting in greater occupancy of the KLF2 promoter by MEF2A. In endothelial cells, the increase in KLF2 and thrombomodulin protein by shRNA-induced decrease in p66shc expression is partly abrogated by knockdown of MEF2A. Finally, knockdown of KLF2 abolishes the decrease in the cellular reactive oxygen species hydrogen peroxide observed with knockdown of p66shc, and KLF2 overexpression suppresses cellular hydrogen peroxide levels, independent of p66shc expression. These findings illustrate a novel mechanism by which p66shc promotes cellular oxidative stress, through suppression of MEF2A expression and consequent repression of KLF2 transcription.
authors.affiliation: Cardiovascular Institute, University of Pittsburgh Medical Center, 623S Scaife Hall, 200 Lothrop St., Pittsburgh, PA 15213, USA. kumara@upmc.edu
authors.forename: Ajay
authors.initials: A
authors.lastname: Kumar
authors.forename: Timothy A
authors.initials: TA
authors.lastname: Hoffman
authors.forename: Jeremy
authors.initials: J
authors.lastname: Dericco
authors.forename: Asma
authors.initials: A
authors.lastname: Naqvi
authors.forename: Mukesh K
authors.initials: MK
authors.lastname: Jain
authors.forename: Kaikobad
authors.initials: K
authors.lastname: Irani
mesh_terms: D000818:Animals; D015536:Down-Regulation; D042783:Endothelial Cells / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D051741:Kruppel-Like Transcription Factors / Q000235:genetics / Q000378:metabolism*; D026161:MADS Domain Proteins / Q000235:genetics / Q000378:metabolism; D064326:MEF2 Transcription Factors; D051379:Mice; D018006:Myogenic Regulatory Factors / Q000235:genetics / Q000378:metabolism; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism; D017382:Reactive Oxygen Species; D055765:Shc Signaling Adaptor Proteins / Q000235:genetics / Q000378:metabolism*; D000071425:Src Homology 2 Domain-Containing, Transforming Protein 1; D014158:Transcription, Genetic
chemical_list: C096161:KLF2 protein, human; D051741:Kruppel-Like Transcription Factors; D026161:MADS Domain Proteins; D064326:MEF2 Transcription Factors; C578035:MEF2A protein, human; D018006:Myogenic Regulatory Factors; D016328:NF-kappa B; D017382:Reactive Oxygen Species; C528024:SHC1 protein, human; D055765:Shc Signaling Adaptor Proteins; D000071425:Src Homology 2 Domain-Containing, Transforming Protein 1
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