title: Isolation of distinct cDNA clones encoding HLA-DR beta chains by use of an expression assay.
abstract: cDNA clones encoding different human Ia antigen beta chains were isolated by use of a complementation-expression assay in Xenopus oocytes. The assay was based on two previous findings. First, oocytes injected with mRNA from a human B-cell line express HLA-DR antigen. The three intracellular DR chains are assembled in oocytes and can be immunoprecipitated with anti-DR monoclonal antibodies. Second, we have isolated cDNA clones encoding DR alpha and intermediate chains. In order to identify beta-chain cDNA clones, mRNA was hybrid-selected with pools of cDNA clones, mixed with mRNA for the alpha and intermediate chains, and injected into oocytes. We isolated two distinct clones that could select DR beta-chain mRNA as demonstrated by assembly of the translation product with DR alpha chains and immunoprecipitation with DR-specific monoclonal antibodies. One clone is specific for a beta chain of the DR locus. The other clone, much weaker in its ability to select DR mRNA, encodes another Ia-like beta chain. Full-length cDNA clones corresponding to the DR and Ia-like beta chains were isolated and compared. Cross-hybridization was detectable in the coding regions but not in the 3' untranslated regions. Distinct RNAs homologous to the DR and the Ia-like beta-chain clones were present in B cells but were undetectable in three T-cell lines.
mesh_terms: D001483:Base Sequence; D003001:Cloning, Molecular; D004247:DNA / Q000235:genetics; D005802:Genes, MHC Class II; D006684:HLA-DR Antigens; D006801:Humans; D046911:Macromolecular Substances; D009693:Nucleic Acid Hybridization; D012333:RNA, Messenger / Q000235:genetics
chemical_list: D006684:HLA-DR Antigens; D046911:Macromolecular Substances; D012333:RNA, Messenger; D004247:DNA