C/EBPbeta serine 64, a phosphoacceptor site, has a critical role in LPS-induced IL-6 and MCP-1 transcription.
C/EBPbeta is a member of the CCAAT/enhancer binding protein family of transcription factors and has been shown to be a critical transcriptional regulator of various proinflammatory genes, including IL-6 and MCP-1. Serine 64 in the transactivation domain of C/EBPbeta has recently been identified as a Ras-induced phosphoacceptor site. The integrity of serine 64 along with threonine 189 is important for the Ha-ras(V12)-induced transformation of NIH3T3 cells, however no target genes dependent upon serine 64 for their expression have been reported. In order to evaluate a potential role of serine 64 in C/EBPbeta-regulated cytokine expression, we expressed a form of C/EBPbeta with an alanine substitution at serine 64 (C/EBPbeta(S64A)) in P388 murine B lymphoblasts, which lack endogenous C/EBPbeta expression and are normally unresponsive to LPS for expression of IL-6 and MCP-1. In comparison to wild type C/EBPbeta, which robustly supports the LPS-induced expression of IL-6 and MCP-1, C/EBPbeta(S64A) was severely impaired in its ability to support the LPS-induced transcription of IL-6 and MCP-1. Furthermore, LPS stimulation increased the level of phosphorylation detected at serine 64. Thus, serine 64, probably through its phosphorylation, is a critical determinant of C/EBPbeta activity in the transcription of IL-6 and MCP-1.
Spooner
Chauncey J
CJ
Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI 48824, USA.
Sebastian
Thomas
T
Shuman
Jon D
JD
Durairaj
Srinivasan
S
Guo
Xiangrong
X
Johnson
Peter F
PF
Schwartz
Richard C
RC
D000818:Animals; D022782:CCAAT-Enhancer-Binding Protein-beta / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D018932:Chemokine CCL2 / Q000235:genetics / Q000378:metabolism*; D017930:Genes, Reporter; D015850:Interleukin-6 / Q000235:genetics / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000276:immunology*; D051379:Mice; D010766:Phosphorylation; D011401:Promoter Regions, Genetic; D012694:Serine / Q000378:metabolism*; D014158:Transcription, Genetic
D022782:CCAAT-Enhancer-Binding Protein-beta; C491768:Ccl2 protein, mouse; D018932:Chemokine CCL2; D015850:Interleukin-6; D008070:Lipopolysaccharides; D012694:Serine