TNF and phorbol esters induce lymphotoxin-beta expression through distinct pathways involving Ets and NF-kappa B family members.
Lymphotoxin-beta (LT-beta) is a transmembrane protein expressed mainly on cells of the lymphoid lineage. It associates with LT-alpha on the cell surface to form the heterotrimeric LTalpha1,beta2 complex, which binds the LT-beta receptor. Membrane lymphotoxin is a crucial signal for the appropriate development of lymph nodes and Peyer's patches, and in the formation of B and T cell compartments in the spleen. In this study we report the characterization of mechanisms governing both basal as well as PMA- and TNF-inducible regulation of the human LT-beta promoter. Using a Jurkat T cell line, induction with either PMA or TNF resulted in an increase in mRNA levels compared with uninduced values. This induction corresponded to an increase in transcriptional activity of the human LT-beta promoter. Mutational and deletion analysis demonstrated the importance of Ets and NF-kappaB motifs in the regulation of basal transcription. Furthermore, the ability of PMA to induce activity was lost in the Ets mutant constructs. Interestingly, the same mutation had little effect on the ability of TNF to induce transcription of the LT-beta promoter. TNF inducibility was localized to the NF-kappaB site positioned at -83 of the promoter sequence. Thus, it appears that the Ets site, although playing a major role in PMA induction, did not mediate TNF inducibility. Therefore, our study suggests that alternative signaling pathways may be present to induce the expression of LT-beta in response to different immunological or inflammatory stimuli.
Voon
Dominic C
DC
Biochemistry and Molecular Biology, School of Biomedical and Chemical Sciences and the Center for Medical Research, University of Western Australia, Crawley, Western Australia, Australia.
Subrata
Lily S
LS
Karimi
Mahdad
M
Ulgiati
Daniela
D
Abraham
Lawrence J
LJ
D001483:Base Sequence; D018983:DNA Footprinting; D003850:Deoxyribonuclease I / Q000235:genetics; D005786:Gene Expression Regulation / Q000187:drug effects / Q000276:immunology; D006801:Humans; D019169:Jurkat Cells; D008233:Lymphotoxin-alpha / Q000037:antagonists & inhibitors / Q000096:biosynthesis* / Q000235:genetics; D053308:Lymphotoxin-beta; D008565:Membrane Proteins / Q000037:antagonists & inhibitors / Q000096:biosynthesis* / Q000235:genetics; D008969:Molecular Sequence Data; D005810:Multigene Family / Q000276:immunology; D016297:Mutagenesis, Site-Directed; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D011401:Promoter Regions, Genetic / Q000187:drug effects / Q000276:immunology; D011518:Proto-Oncogene Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D050783:Proto-Oncogene Proteins c-ets; D012333:RNA, Messenger / Q000096:biosynthesis; D034741:RNA, Small Interfering / Q000494:pharmacology; D017384:Sequence Deletion / Q000276:immunology; D016329:Sp1 Transcription Factor / Q000235:genetics / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D051996:Transcription Factor RelA; D014157:Transcription Factors / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D014409:Tumor Necrosis Factor-alpha / Q000037:antagonists & inhibitors / Q000502:physiology*; D015854:Up-Regulation / Q000187:drug effects / Q000276:immunology
C505886:LTB protein, human; D008233:Lymphotoxin-alpha; D053308:Lymphotoxin-beta; D008565:Membrane Proteins; D016328:NF-kappa B; D011518:Proto-Oncogene Proteins; D050783:Proto-Oncogene Proteins c-ets; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D016329:Sp1 Transcription Factor; D051996:Transcription Factor RelA; D014157:Transcription Factors; D014409:Tumor Necrosis Factor-alpha; D003850:Deoxyribonuclease I; D013755:Tetradecanoylphorbol Acetate