title: Isolation of an excision product of T-cell receptor alpha-chain gene rearrangements.
abstract: The genes for the T-cell receptor, like the immunoglobulin genes, are rearranged as DNA. The mechanism of this rearrangement is not clear; unequal crossover between chromosomes and the looping-out and excision of the excess DNA have both been suggested. We isolated small polydisperse circular (spc) DNAs from mouse thymocytes and cloned them into a phage vector. Of the 56 clones we analysed, nine contained sequences homologous to T-cell receptor alpha-chain joining (J alpha) segments. We have characterized one of these clones; it contains one J alpha segment, and the product out of the recombination of a variable region of the alpha-chain gene (V alpha) with a J alpha gene segment. This is the first demonstration of the presence in extrachromosomal DNA of a reciprocal recombination product of any rearranging immunoglobulin or T-cell receptor gene. The finding verifies that V alpha-J alpha joining can occur by the looping-out and excision of chromosomal DNA.
mesh_terms: D000818:Animals; D010582:Bacteriophage lambda / Q000235:genetics; D001483:Base Sequence; D003001:Cloning, Molecular; D004262:DNA Restriction Enzymes; D004270:DNA, Circular / Q000235:genetics*; D007135:Immunoglobulin Variable Region / Q000235:genetics; D046911:Macromolecular Substances; D051379:Mice; D009693:Nucleic Acid Hybridization; D011948:Receptors, Antigen, T-Cell / Q000235:genetics*; D011995:Recombination, Genetic
chemical_list: D004270:DNA, Circular; D007135:Immunoglobulin Variable Region; D046911:Macromolecular Substances; D011948:Receptors, Antigen, T-Cell; D004262:DNA Restriction Enzymes