Mapping of the interaction site of the defective transcription factor in the class II major histocompatibility complex mutant cell line clone-13 to the divergent X2-box.
We have previously described a mutant B lymphoblastoid cell line, Clone-13, that expresses HLA-DQ in the absence of HLA-DR and -DP. Several criteria indicated that the defect in this cell line influences the activity of an isotype-specific transcription factor. Indeed, transient transfection of HLA-DRA and DQB reporter constructs indicated that the affected factor operates via cis-elements located between -141 base pairs and the transcription initiation site. A series of hybrid DRA/DQB reporter constructs was generated to further map the relevant cis-elements in this system. Insertion of oligonucleotides spanning the DQB X-box (but not the DQB-W region or the DQB Y-box) upstream of -141 in a DRA reporter plasmid rescued expression to nearly wild-type levels. Substitution promoters were then generated where the entire X-box, or only the X1- or X2-boxes of HLA-DRA were replaced with the analogous regions of HLA-DQB. The DQB X2-box was able to restore expression to the silent DRA reporter construct. Moreover, replacement of the DQB X2-box with the DRA X2-box markedly diminished the activity of the DQB promoter in the mutant cell. None of the hybrid reporter constructs were defective when transfected into the wild-type, HLA-DR/-DQ positive parental cell line, Jijoye. These studies suggest that the divergent X2-box of the class II major histocompatibility complex promoters plays an important role in influencing differential expression of the human class II isotypes.
Ono
S J
SJ
Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland 21224.
Song
Z
Z
D001402:B-Lymphocytes / Q000276:immunology; D001483:Base Sequence; D001665:Binding Sites; D002999:Clone Cells; D017931:DNA Primers; D015870:Gene Expression; D005802:Genes, MHC Class II; D006683:HLA-DQ Antigens / Q000096:biosynthesis* / Q000235:genetics; D059866:HLA-DQ beta-Chains; D006684:HLA-DR Antigens / Q000096:biosynthesis* / Q000235:genetics; D059805:HLA-DR alpha-Chains; D006801:Humans; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D009154:Mutation; D011401:Promoter Regions, Genetic; D012045:Regulatory Sequences, Nucleic Acid; D014157:Transcription Factors / Q000378:metabolism*; D014162:Transfection; D014407:Tumor Cells, Cultured
D017931:DNA Primers; D006683:HLA-DQ Antigens; D059866:HLA-DQ beta-Chains; C057615:HLA-DQbeta antigen; D006684:HLA-DR Antigens; D059805:HLA-DR alpha-Chains; D014157:Transcription Factors