Expression of the MHC class II transactivator (CIITA) type IV promoter in B lymphocytes and regulation by IFN-gamma.
The MHC class II transactivator (CIITA), the master regulator of MHC class II (MHC II) expression, is a co-activator that controls MHC II transcription. Human B lymphocytes express MHC II constitutively due to persistent activity of CIITA promoter III (pIII), one of the four potential promoters (pI-pIV) of this gene. Although increases in MHC II expression in B cells in response to cytokines have been observed and induction of MHC II and CIITA by IFN-gamma has been studied in a number of different cell types, the specific effects of IFN-gamma on CIITA expression in B cells have not been studied. To investigate the regulation of CIITA expression by IFN-gamma in B cells, RT-PCR, in vivo and in vitro protein/DNA binding studies, and functional promoter analyses were performed. Both MHC II and CIITA type IV-specific RNAs increased in human B lymphocytes in response to IFN-gamma treatment. CIITA promoter analysis confirmed that pIV is IFN-gamma inducible in B cells and that the GAS and IRF-E sites are necessary for full induction. DNA binding of IRF-1 and IRF-2, members of the IFN regulatory factor family, was up-regulated in B cells in response to IFN-gamma and increased the activity of CIITA pIV. In vivo genomic footprint analysis demonstrated proteins binding at the GAS, IRF-E and E box sites of CIITA pIV. Although CIITA pIII is considered to be the hematopoietic-specific promoter of CIITA, these findings demonstrate that pIV is active in B lymphocytes and potentially contributes to the expression of CIITA and MHC II in these cells.
Piskurich
Janet F
JF
Division of Basic Sciences, Mercer University School of Medicine, 1550 College St., Macon, GA 31207, USA. Piskurich_J@Mercer.edu
Gilbert
Carolyn A
CA
Ashley
Brittany D
BD
Zhao
Mojun
M
Chen
Han
H
Wu
Jian
J
Bolick
Sophia C
SC
Wright
Kenneth L
KL
D001402:B-Lymphocytes / Q000378:metabolism*; D001665:Binding Sites; D004268:DNA-Binding Proteins; D005786:Gene Expression Regulation / Q000187:drug effects / Q000276:immunology*; D000949:Histocompatibility Antigens Class II / Q000235:genetics; D006801:Humans; D050856:Interferon Regulatory Factor-1 / Q000378:metabolism; D050836:Interferon Regulatory Factor-2 / Q000378:metabolism; D007371:Interferon-gamma / Q000494:pharmacology*; D009687:Nuclear Proteins / Q000235:genetics*; D011401:Promoter Regions, Genetic / Q000235:genetics*; D011485:Protein Binding; D012333:RNA, Messenger / Q000032:analysis; D015534:Trans-Activators / Q000235:genetics*
D004268:DNA-Binding Proteins; D000949:Histocompatibility Antigens Class II; C494229:IRF2 protein, human; D050856:Interferon Regulatory Factor-1; D050836:Interferon Regulatory Factor-2; C083728:MHC class II transactivator protein; D009687:Nuclear Proteins; D012333:RNA, Messenger; D015534:Trans-Activators; D007371:Interferon-gamma