UNEQUAL HOMOLOGOUS RECOMBINATION OF HUMAN DNA ON A YEAST ARTIFICIAL CHROMOSOME

We examined unequal homologous DNA recombination between human repetit ive DNA elements located on a yeast artificial chromosome (YAC) and tr ansforming plasmid molecules, A plasmid vector containing an Alu eleme nt, as well as a sequence identical to a unique site on a YAC, was int roduced into yeast and double recombinant clones analyzed, Recombinati on occurs between vector and YAC Alu elements sharing as little as 74% identity, The physical proximity of an Alu element to the unique DNA segment appears to play a significant role in determining the frequenc y with which that element serves as a recombination substrate, In addi tion, cross-over points of the recombination reaction are largely conf ined to the ends of the repetitive element, Since a similar distributi on of crossover sites occurs during unequal homologous recombination i n human germ and somatic tissue, we propose that similar enzymatic pro cesses may be responsible for the events observed in our system and in human cells, This suggests that further examination of the enzymology of unequal homologous recombination of human DNA within yeast may yie ld a greater understanding of the molecular events which control this process in higher eukaryotes.