RSK-Mediated Phosphorylation in the C/EBPβ Leucine Zipper Regulates DNA Binding, Dimerization, and Growth Arrest Activity

被引:59
|
作者
Lee, Sook [1 ]
Shuman, Jon D. [1 ]
Guszczynski, Tad [2 ]
Sakchaisri, Krisada [1 ]
Sebastian, Thomas [1 ]
Copeland, Terry D. [2 ]
Miller, Maria [3 ]
Cohen, Michael S. [4 ,5 ]
Taunton, Jack [4 ,5 ]
Smart, Robert C. [6 ]
Xiao, Zhen [7 ]
Yu, Li-Rong [7 ]
Veenstra, Timothy D. [7 ]
Johnson, Peter F. [1 ]
机构
[1] NCI, Lab Canc Prevent, Ctr Canc Res, Frederick, MD 21702 USA
[2] NCI, Lab Cell & Dev Signaling, Ctr Canc Res, Frederick, MD 21702 USA
[3] NCI, Macromol Crystallog Lab, Ctr Canc Res, Frederick, MD 21702 USA
[4] Univ Calif San Francisco, Program Chem & Chem Biol, San Francisco, CA 94143 USA
[5] Univ Calif San Francisco, Dept Cellular & Mol Pharmacol, San Francisco, CA 94143 USA
[6] N Carolina State Univ, Dept Environm & Mol Toxicol, Raleigh, NC 27695 USA
[7] SAIC Frederick Inc, Adv Technol Program, Lab Prote & Analyt Technol, Frederick, MD 21702 USA
关键词
MITOTIC CLONAL EXPANSION; ONCOGENE-INDUCED SENESCENCE; PROTEIN-BETA; TRANSCRIPTIONAL ACTIVATOR; HEPATOCYTE PROLIFERATION; CELL PROLIFERATION; NUCLEAR FACTOR; MAMMARY-GLAND; DIFFERENTIATION; ADIPOGENESIS;
D O I
10.1128/MCB.00782-09
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
The bZIP transcription factor C/EBP beta is a target of Ras signaling that has been implicated in Ras-induced transformation and oncogene-induced senescence (OIS). To gain insights into Ras-C/EBP beta signaling, we investigated C/EBP beta activation by oncogenic Ras. We show that C/EBP beta DNA binding is autorepressed and becomes activated by the Ras-Raf-MEK-ERK-p90(RSK) cascade. Inducible phosphorylation by RSK on Ser273 in the leucine zipper was required for DNA binding. In addition, three other modifications (phosphorylation on Tyr109 [p-Tyr109], p-Ser111, and monomethylation of Arg114 [me-Arg114]) within an N-terminal autoinhibitory domain were important for Ras-induced C/EBP beta activation and cytostatic activity. Apart from its role in DNA binding, Ser273 phosphorylation also creates an interhelical g <-> e ' salt bridge with Lys268 that increases attractive electrostatic interactions between paired leucine zippers and promotes homodimerization. Mutating Ser273 to Ala or Lys268 to Glu decreased C/EBP beta homodimer formation, whereas heterodimerization with C/EBP gamma was relatively unaffected. The S273A substitution also reduced the antiproliferative activity of C/EBP beta in Ras(V12)-expressing fibroblasts and decreased binding to target cell cycle genes, while a phosphomimetic substitution (S273D) maintained growth arrest function. Our findings identify four novel C/EBP beta-activating modifications, including RSK-mediated phosphorylation of a bifunctional residue in the leucine zipper that regulates DNA binding and homodimerization and thereby promotes cell cycle arrest.
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页码:2621 / 2635
页数:15
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