Regulation and specificity of MHC2TA promoter usage in human primary T lymphocytes and cell line.
Although activated human T cells express MHC class II antigens, the regulation of these antigens in T cells is poorly understood. This study focuses on the control of the MHC2TA gene in these cells. MHC2TA encodes the transcriptional master regulator of MHC class II, the class II trans-activator (CIITA). It has at least three distinct promoters (PI, PIII, and PIV), each active in an overlapping subset of cell types and directing a slightly different product. This report used highly purified blood T cells prepared by negative immunoselection to analyze CIITA. Real-time PCR analysis indicates that resting T cells do not express detectable CIITA transcript, while activated T cells express the PIII CIITA form. Transient transfection of activated blood T cells using wild-type and mutant PIII promoter-reporter constructs shows that two promoter elements, activation response element-1 (ARE-1) and ARE-2, are important for PIII function. cAMP response element binding protein, a known activator of gene expression in activated T cells, activates PIII in primary T cells. However, an intact ARE-2 site is not required for this activation, indicating that cAMP response element binding protein does not activate via this site. EMSAs indicate that an activating transcription factor/cAMP response element binding protein/cAMP response element modulator family member, but not phosphorylated cAMP response element binding protein-1, binds to ARE-2. ARE-2 also forms a complex with an unidentified protein. The ARE-2 binding protein is constitutively expressed in a DR(+) T cell line, reflecting differences between the DR(+) cell line and primary blood lymphocytes. These results show that MHC2TA PIII is induced in activated T lymphocytes, and that the induced binding of ARE-2 is a crucial step in this process.
Wong
Athena W
AW
Curriculum in Genetics and Molecular Biology, University of North Carolina, Chapel Hill, NC 27599, USA.
Ghosh
Nilanjan
N
McKinnon
Karen P
KP
Reed
William
W
Piskurich
Janet F
JF
Wright
Kenneth L
KL
Ting
Jenny P-Y
JP
D000217:Acyltransferases / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D001483:Base Sequence; D002478:Cells, Cultured; D017362:Cyclic AMP Response Element-Binding Protein / Q000502:physiology; D056850:Cyclin-Dependent Kinase 8; D018844:Cyclin-Dependent Kinases / Q000235:genetics / Q000502:physiology; D018984:Epitopes, T-Lymphocyte / Q000235:genetics* / Q000378:metabolism; D005786:Gene Expression Regulation / Q000276:immunology*; D006684:HLA-DR Antigens / Q000096:biosynthesis; D006801:Humans; D007399:Interphase / Q000235:genetics / Q000276:immunology; D008213:Lymphocyte Activation / Q000235:genetics; D008969:Molecular Sequence Data; D009687:Nuclear Proteins; D010835:Phytohemagglutinins / Q000494:pharmacology; D011401:Promoter Regions, Genetic / Q000276:immunology*; D011485:Protein Binding / Q000235:genetics / Q000276:immunology; D020218:Response Elements / Q000276:immunology; D029701:Saccharomyces cerevisiae Proteins; D016176:T-Lymphocyte Subsets / Q000166:cytology / Q000276:immunology* / Q000378:metabolism*; D015534:Trans-Activators / Q000096:biosynthesis / Q000235:genetics* / Q000502:physiology; D014407:Tumor Cells, Cultured
D017362:Cyclic AMP Response Element-Binding Protein; D018984:Epitopes, T-Lymphocyte; D006684:HLA-DR Antigens; C083728:MHC class II transactivator protein; D009687:Nuclear Proteins; D010835:Phytohemagglutinins; D029701:Saccharomyces cerevisiae Proteins; D015534:Trans-Activators; D000217:Acyltransferases; D056850:Cyclin-Dependent Kinase 8; D018844:Cyclin-Dependent Kinases; C498309:SSN3 protein, S cerevisiae