Bacterial peptidoglycan-induced tnf-alpha transcription is mediated through the transcription factors Egr-1, Elk-1, and NF-kappaB.
Bacteria and their ubiquitous cell wall component peptidoglycan (PGN) activate the innate immune system of the host and induce the release of inflammatory molecules. TNF-alpha is one of the highest induced cytokines in macrophages stimulated with PGN; however, the regulation of tnf-alpha expression in PGN-activated cells is poorly understood. This study was done to identify some of the transcription factors that regulate the expression of the tnf-alpha gene in macrophages stimulated with PGN. Our results demonstrated that PGN-induced expression of human tnf-alpha gene is regulated by sequences proximal to -182 bp of the promoter. Mutations within the binding sites for cAMP response element, early growth response (Egr)-1, and kappaB3 significantly reduced this induction. The transcription factor c-Jun bound the cAMP response element site, Egr-1 bound the Egr-1 motif, and NF-kappaB p50 and p65 bound to the kappaB3 site on the tnf-alpha promoter. PGN rapidly induced transcription of egr-1 gene and this induction was significantly reduced by specific mutations within the serum response element-1 domain of the egr-1 promoter. PGN also induced phosphorylation and activation of Elk-1, a member of the Ets family of transcription factors. Elk-1 and serum response factor proteins bound the serum response element-1 domain on the egr-1 promoter, and PGN-induced expression of the egr-1 was inhibited by dominant-negative Elk-1. These results indicate that PGN induces activation of the transcription factors Egr-1 and Elk-1, and that PGN-induced expression of tnf-alpha is directly mediated through the transcription factors c-Jun, Egr-1, and NF-kappaB, and indirectly through the transcription factor Elk-1.
Xu
Z
Z
Northwest Center for Medical Education, Indiana University School of Medicine, Gary, IN 46408, USA.
Dziarski
R
R
Wang
Q
Q
Swartz
K
K
Sakamoto
K M
KM
Gupta
D
D
D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000235:genetics / Q000502:physiology*; D051766:Early Growth Response Protein 1; D006801:Humans; D017874:Immediate-Early Proteins; D008264:Macrophages / Q000187:drug effects / Q000276:immunology*; D051379:Mice; D008837:Micrococcus / Q000502:physiology; D009154:Mutation; D016328:NF-kappa B / Q000502:physiology*; D010457:Peptidoglycan / Q000494:pharmacology*; D010766:Phosphorylation; D011401:Promoter Regions, Genetic; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000502:physiology*; D016755:Proto-Oncogene Proteins c-jun / Q000502:physiology; D012333:RNA, Messenger / Q000096:biosynthesis; D020218:Response Elements; D014157:Transcription Factors / Q000235:genetics / Q000502:physiology*; D015533:Transcriptional Activation; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics*; D050807:ets-Domain Protein Elk-1
D004268:DNA-Binding Proteins; C497325:EGR1 protein, human; C494112:ELK1 protein, human; D051766:Early Growth Response Protein 1; C486109:Egr1 protein, mouse; C494113:Elk1 protein, mouse; D017874:Immediate-Early Proteins; D016328:NF-kappa B; D010457:Peptidoglycan; D011518:Proto-Oncogene Proteins; D016755:Proto-Oncogene Proteins c-jun; D012333:RNA, Messenger; D014157:Transcription Factors; D014409:Tumor Necrosis Factor-alpha; D050807:ets-Domain Protein Elk-1