Induction of the CTLA-4 gene in human lymphocytes is dependent on NFAT binding the proximal promoter.
CTLA-4 is a member of the costimulatory family, has homology to CD28, and binds the B7 family of ligands. Unlike CD28, CTLA-4 ligation transmits a negative signal in T cells. CTLA-4 expression, while inducible in most T cells, is expressed constitutively on T cells with a regulatory phenotype. The mechanism controlling CTLA-4 expression in human T cells is poorly characterized, thus we sought to better understand the mechanism of activation of the CTLA-4 gene. By cloning the 5' upstream promoter and creating promoter-deletion reporter constructs, we show that the proximal promoter is critical for activating the CTLA-4 gene. Within this region, we identify a NFAT consensus sequence that binds NFAT with high affinity that differs from other NFAT sequences and does not recruit AP-1. Analysis of the chromatin proteins in the native CTLA-4 gene shows that this promoter region becomes associated with acetylated histones by chromatin immunoprecipitation assays. In addition, NFAT1 binds to the promoter of the CTLA-4 gene after stimulation by chromatin immunoprecipitation. The functional requirement of the NFAT site for CTLA-4 transcription was demonstrated by mutations in the NFAT site that abolished the activity of the promoter. Furthermore, inhibitors of NFAT suppressed CTLA-4 gene expression, indicating that NFAT plays a critical role in regulating the induction of the CTLA-4 gene in lymphocytes. The identification of NFAT as a critical regulator of the CTLA-4 gene suggests that targeting NFAT function may lead to novel approaches to modulate the CTLA-4 gene to control the immune response.
Gibson
Heather M
HM
Department of Dermatology, Henry Ford Hospital, Detroit, MI 48202, USA.
Hedgcock
Carrie J
CJ
Aufiero
Barbara M
BM
Wilson
Adam J
AJ
Hafner
Mikehl S
MS
Tsokos
George C
GC
Wong
Henry K
HK
D020121:5' Untranslated Regions / Q000276:immunology / Q000378:metabolism; D015703:Antigens, CD / Q000096:biosynthesis* / Q000235:genetics* / Q000378:metabolism; D000943:Antigens, Differentiation / Q000096:biosynthesis* / Q000235:genetics* / Q000378:metabolism; D060908:CTLA-4 Antigen; D002478:Cells, Cultured; D016384:Consensus Sequence / Q000235:genetics / Q000276:immunology; D005786:Gene Expression Regulation / Q000276:immunology*; D006801:Humans; D050778:NFATC Transcription Factors / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D011401:Promoter Regions, Genetic / Q000276:immunology; D011485:Protein Binding / Q000235:genetics / Q000276:immunology; D012333:RNA, Messenger / Q000096:biosynthesis; D016176:T-Lymphocyte Subsets / Q000276:immunology* / Q000378:metabolism*; D015854:Up-Regulation / Q000276:immunology