conserved and distinct modes of crebatf transcription factor regulation by pp2ab56γ and genotoxic stress守恒和不同模式由pp2ab56γcrebatf转录因子调控,基因毒性压力.pdf

Conserved and Distinct Modes of CREB/ATF Transcription Factor Regulation by PP2A/B56c and Genotoxic Stress Naval P. Shanware, Lihong Zhan, John A. Hutchinson, Sang Hwa Kim, Leah M. Williams, Randal S. Tibbetts* Department of Pharmacology, Program in Molecular and Cellular Pharmacology and Molecular and Environmental and Toxicology Center, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, United States of America Abstract Activating transcription factor 1 (ATF1) and the closely related proteins CREB (cyclic AMP resonse element binding protein) and CREM (cyclic AMP response element modulator) constitute a subfamily of bZIP transcription factors that play critical roles in the regulation of cellular growth, metabolism, and survival. Previous studies demonstrated that CREB is phosphorylated on a cluster of conserved Ser residues, including Ser-111 and Ser-121, in response to DNA damage through the coordinated actions of the ataxia-telangiectasia-mutated (ATM) protein kinase and casein kinases 1 and 2 (CK1/2). Here, we show that DNA damage-induced phosphorylation by ATM is a general feature of CREB and ATF1. ATF1 harbors a conserved ATM/CK cluster that is constitutively and stoichiometrically phosphorylated by CK1 and CK2 in asynchronously growing cells. Exposure to DNA damage further induced ATF1 phosphorylation on Ser-51 by ATM in a manner that required prior phosphorylation of the upstream CK residues. Hyperphosphorylated ATF1 showed a 4-fold reduced affinity for CREB- binding protein. We further show that PP2A, in conjunction with its targeting subunit B56c, antagonized ATM and CK1/2- dependent phosphorylation of CREB and ATF1 in cellulo. Finally, we show that CK sites in CREB are phosphorylated during cellular growth and that phosphorylation of these residues reduces the threshold of D