In vivo, RFX5 binds differently to the human leucocyte antigen-E, -F, and -G gene promoters and participates in HLA class I protein expression in a cell type-dependent manner.
We analysed the regulation of human leucocyte antigen (HLA)-E, -F and -G genes, focusing on the SXY module, a promoter region that controls major histocompatibility complex (MHC) class II expression and participates in the expression of classical HLA class I molecules. It comprises the X1, X2 and Y boxes, bound by RFX, X2-BP/ATF/CREB and NFY factors, respectively. The complex recruits the master control factor CIITA. The SXY module is conserved in HLA-E and HLA-F gene promoters, whereas in the HLA-G promoter, the only conserved boxes are S and X1. Chromatin immunoprecipitation assays, performed on HLA-G positive and negative cell lines, demonstrated the in situ binding of RFX5 and CIITA to HLA-E and HLA-F, but not to HLA-G, promoters. In B cells from bare lymphocyte syndrome patients lacking RFX5 or CIITA, we observed lower steady-state levels of HLA-E and HLA-F transcripts but did not find any significant decrease in the cell-surface expression of HLA-E/classical HLA class I. In RFX5-deficient fibroblasts, the cell-surface expression of HLA molecules was decreased. RFX5 and CIITA are thus not involved in HLA-G expression and their importance for the surface expression of HLA-E/classical HLA class I molecules may vary depending on the cell type.
Rousseau
Philippe
P
CEA, Service de Recherche en Hémato-Immunologie, DSV/DRM, Hôpital Saint-Louis, Institut Universitaire d'Hématologie, Paris, France.
Masternak
Krzysztof
K
Krawczyk
Michal
M
Reith
Walter
W
Dausset
Jean
J
Carosella
Edgardo D
ED
Moreau
Philippe
P
D001402:B-Lymphocytes / Q000378:metabolism*; D002461:Cell Line, Transformed; D045744:Cell Line, Tumor; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005347:Fibroblasts / Q000378:metabolism; D005434:Flow Cytometry; D005805:Genes, MHC Class I; D006680:HLA Antigens / Q000235:genetics; D059951:HLA-G Antigens; D015395:Histocompatibility Antigens Class I / Q000235:genetics; D006801:Humans; D015151:Immunoblotting / Q000379:methods; D009687:Nuclear Proteins; D011233:Precipitin Tests / Q000379:methods; D011401:Promoter Regions, Genetic; D000071701:Regulatory Factor X Transcription Factors; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015534:Trans-Activators / Q000378:metabolism*; D000097625:HLA-E Antigens
D004268:DNA-Binding Proteins; D006680:HLA Antigens; D059951:HLA-G Antigens; D015395:Histocompatibility Antigens Class I; D009687:Nuclear Proteins; D000071701:Regulatory Factor X Transcription Factors; D015534:Trans-Activators; D000097625:HLA-E Antigens; C062341:HLA-F antigens; C083728:MHC class II transactivator protein; C093524:RFX5 protein, human