Combinations of dominant-negative class II transactivator, p300 or CDK9 proteins block the expression of MHC II genes.
The class II transactivator (CIITA) regulates not only the transcription of HLA-DR, -DQ, -DP, but also invariant chain, DMA and DMB genes. A hybrid mutant CIITA protein, which contained residues from positions 302 to 1130 in CIITA fused to the enhanced green fluorescent protein (EdCIITA), inhibited the function of the wild-type protein. EdCIITA extinguished the inducible and constitutive expression of MHC II genes in epithelial cells treated with IFN-gamma and B lymphoblastoid cells respectively. Also, it blocked T cell activation by superantigen. This inhibition correlated with the localization of EdCIITA but not CIITA in the cytoplasm of cells. However, when EdCIITA was co-expressed with a dominant-negative form of the nucleoporin Nup214/CAN, it also accumulated in the nucleus. These data suggest that EdCIITA not only competes with the wild-type protein for the binding to MHC II promoters but sequesters a critical co-factor of CIITA in the cytoplasm. CIITA also recruits the histone acetyltransferase cAMP responsive element binding protein (CREB) binding protein and positive transcription elongation factor b (p-TEFb) for the transcription of MHC II genes. Dominant-negative p300 (DNp300) or CDK9 (DNCDK9) proteins inhibited the function of CIITA and of the DRA promoter. Thus, combinations of EdCIITA and DNp300 and/or DNCDK9 proteins extinguished the transcription of MHC II genes. They might become useful for future genetic therapeutic approaches in organ transplantation and autoimmune diseases.
Kanazawa
S
S
Department of Medicine, Howard Hughes Medical Institute, University of California, San Francisco, CA 94143-0703, USA.
Peterlin
B M
BM
D000818:Animals; D019556:COS Cells; D002522:Chlorocebus aethiops; D042863:Cyclin-Dependent Kinase 9; D018844:Cyclin-Dependent Kinases / Q000235:genetics / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism; D015870:Gene Expression; D015696:Gene Products, tat / Q000378:metabolism; D005802:Genes, MHC Class II; D006367:HeLa Cells; D006801:Humans; D007371:Interferon-gamma / Q000378:metabolism; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic; D015533:Transcriptional Activation
D015696:Gene Products, tat; C083728:MHC class II transactivator protein; D009687:Nuclear Proteins; D011993:Recombinant Fusion Proteins; D015534:Trans-Activators; D007371:Interferon-gamma; C467969:CDK9 protein, human; D042863:Cyclin-Dependent Kinase 9; D018844:Cyclin-Dependent Kinases