THE INFLUENCE OF A (GT)(29) MICROSATELLITE SEQUENCE ON HOMOLOGOUS RECOMBINATION IN THE HAMSTER ADENINE PHOSPHORIBOSYLTRANSFERASE GENE

Several DNA sequence elements are thought to stimulate homologous reco mbination, illegitimate recombination, or both in mammalian cells. Som e are implicated by their recurrence around rearrangement breakpoints, others by their effects on recombination of extrachromosomal plasmids . None of these sequences, however, has been tested on the chromosome in a defined context. In this paper we show how the adenine phosphorib osyltransferase locus in CHO cells can be used to study the recombinog enic potential of defined DNA sequences. As an example we have measure d the effect on homologous recombination of a dinucleotide repeat, (GT )(29), which has been shown to stimulate homologous recombination in e xtrachromosomal vectors 3-20-fold. On the chromosome at the adenine ph osphoribosyltransferase locus, however, this sequence shows no capacit y to stimulate recombination or to influence the distribution of recom bination events.