GENE CONVERSION IN THE CHICKEN IMMUNOGLOBULIN LOCUS - A PARADIGM OF HOMOLOGOUS RECOMBINATION IN HIGHER EUKARYOTES

Gene conversion was first defined in yeast as a type of homologous rec ombination in which the donor sequence does not change. In chicken B c ells, gene conversion builds the antigen receptor repertoire by introd ucing sequence diversity into the immunoglobulin genes. Immunoglobulin gene conversion continues at high frequency in an avian leukosis viru s induced chicken B cell line. This cell line can be modified by homol ogous integration of transfected DNA constructs offering a model syste m for studying gene conversion in higher eukaryotes. In search for gen es which might participate in chicken immunoglobulin gene conversion, we have identified chicken counterparts of the yeast RAD51, RAD52, and RAD54 genes. Disruption and overexpression of these genes in the chic ken B cell line may clarify their role in gene conversion and gene tar geting.