title: T cell receptor beta gene sequences in the circular DNA of thymocyte nuclei: direct evidence for intramolecular DNA deletion in V-D-J joining.
abstract: We have identified circular DNA containing T cell receptor (TCR) beta gene sequences in mouse thymocytes, thereby providing direct evidence for the intramolecular DNA deletion model of V-D-J joining in TCR beta genes. Two types of excision products of V-D-J joining have been identified. Type I, a circular reciprocal recombinant of normal V-D or D-J joining, contains a 7mer-7mer head-to-head structure expected from an excised product of normal V-D or D-J joining. Type II contains a D beta 2-J beta 1 structure on the circular DNA; the recombination event producing this molecule occurs between an upstream J and a downstream D segment, probably leaving the reciprocal 7mer-7mer structure on the chromosome. Some type I molecules seem to represent excision products of secondary joining after formation of the first D-J or V-D-J structure. The recombination mechanism that generates the circular DNA is discussed.
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002467:Cell Nucleus / Q000378:metabolism; D002872:Chromosome Deletion; D004270:DNA, Circular / Q000235:genetics* / Q000302:isolation & purification; D004274:DNA, Recombinant / Q000378:metabolism*; D005796:Genes; D014644:Genetic Variation; D051379:Mice; D008807:Mice, Inbred BALB C; D011948:Receptors, Antigen, T-Cell / Q000235:genetics*; D013601:T-Lymphocytes / Q000276:immunology*; D013950:Thymus Gland / Q000276:immunology
chemical_list: D004270:DNA, Circular; D004274:DNA, Recombinant; D011948:Receptors, Antigen, T-Cell