Antioxidant-induced nuclear translocation of CCAAT/enhancer-binding protein beta. A critical role for protein kinase A-mediated phosphorylation of Ser299.

Abstract	Alterations in intracellular oxidative status activate several signal transduction pathways resulting in distinct patterns of gene expression. Treatment of colorectal cancer cells with antioxidants can lead to apoptosis by induction of p21 through a mechanism involving CCAAT/enhancer-binding protein beta (C/EBPbeta). Herein, we demonstrate that the antioxidant pyrrolidinedithiocarbamate activates cAMP-dependent protein kinase (PKA) in a colorectal cancer cell line DKO-1. Activation of PKA phosphorylates Ser299 within C/EBPbeta, which is essential for protein translocation to the nucleus. Pharmacological inhibition of PKA and mutation of Ser299 to alanine blocks C/EBPbeta nuclear translocation and induction of p21. Our results indicate that a cAMP-dependent phosphorylation of C/EBPbeta at Ser299 is critical for nuclear translocation of this protein and its subsequent transactivation of genes in response to antioxidant treatment.
Authors	R Chinery, J A Brockman, D T Dransfield, R J Coffey
Journal	The Journal of biological chemistry (J Biol Chem) Vol. 272 Issue 48 Pg. 30356-61 (Nov 28 1997) ISSN: 0021-9258 [Print] United States
PMID	9374525 (Publication Type: Journal Article, Research Support, U.S. Gov't, P.H.S.)
Chemical References	Antioxidants CCAAT-Enhancer-Binding Proteins DNA-Binding Proteins Nuclear Proteins RNA, Messenger Thiocarbamates prolinedithiocarbamate Phosphoserine Colforsin Proline Hydrogen Peroxide Cyclic AMP Cyclic AMP-Dependent Protein Kinases HRAS protein, human Proto-Oncogene Proteins p21(ras)
Topics	Antioxidants (pharmacology) Biological Transport CCAAT-Enhancer-Binding Proteins Cell Compartmentation Colforsin (pharmacology) Cyclic AMP (metabolism) Cyclic AMP-Dependent Protein Kinases (metabolism) DNA-Binding Proteins (metabolism) Humans Hydrogen Peroxide (metabolism) Leucine Zippers Nuclear Proteins (metabolism) Phosphoserine (metabolism) Proline (analogs & derivatives, pharmacology) Protein Processing, Post-Translational (drug effects) Proto-Oncogene Proteins p21(ras) (metabolism) RNA, Messenger (genetics) Thiocarbamates (pharmacology) Tumor Cells, Cultured

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