title: Germ-line sequence of the DH segment employed in Ars-A antibodies: implications for the generation of junctional diversity.
abstract: The majority of antibodies produced by A/J mice in response to p-azophenylarsonate belong to the Ars-A family. These antibodies have the conserved sequence cys-ala-arg-ser-x-tyr-tyr (in which x is variable) spanning the V-D junction of the heavy chain. The cys-ala-arg residues are accounted for in the sequence of the A/J VH gene; the tyr-tyr are believed to be specified by the A/J DH segment, although this assumption is based on the DFL16.1 sequence derived from BALB/c mice. This implies that the ser-x is generated by joining imprecision and/or N segment addition. More recent data have revealed that the codon specifying the junctional serine residue is highly conserved (TCN, where N is usually G), suggesting a germline origin. Because there is no obvious way to generate this codon from the A/J Ars-A VH gene, we examined the involvement of the A/J DH segment in the generation of this junctional residue by cloning and sequencing the A/J equivalent to DFL16.1. We have established that this DH segment is polymorphic among BALB/c and A/J at the nucleic acid sequence level, and that it does not encode the junctional serine. This implies that a mechanism other than joining imprecision or random N segment addition operates at V-D junctions of Ars-A heavy chains.
mesh_terms: D000818:Animals; D000916:Antibody Diversity; D001391:Azo Compounds / Q000276:immunology*; D003001:Cloning, Molecular; D004262:DNA Restriction Enzymes; D005796:Genes; D007143:Immunoglobulin Heavy Chains / Q000235:genetics*; D007135:Immunoglobulin Variable Region / Q000235:genetics*; D051379:Mice; D008805:Mice, Inbred A; D008807:Mice, Inbred BALB C; D009693:Nucleic Acid Hybridization; D014176:Protein Biosynthesis; D013045:Species Specificity; D010132:p-Azobenzenearsonate / Q000276:immunology*
chemical_list: D001391:Azo Compounds; D007143:Immunoglobulin Heavy Chains; D007135:Immunoglobulin Variable Region; D010132:p-Azobenzenearsonate; D004262:DNA Restriction Enzymes