HAMSTER CHROMOSOMES CONTAINING AMPLIFIED HUMAN ALPHA-SATELLITE DNA SHOW DELAYED SISTER-CHROMATID SEPARATION IN THE ABSENCE OF DE-NOVO KINETOCHORE FORMATION

The centromeres of human chromosomes contain large amounts of the tand emly repeated alpha-satellite DNA family. Previous studies have shown that integration of alpha-satellite DNA into ectopic locations in mamm alian chromosomes can result in the de novo formation of several featu res of centromeric function. Here we further examine the possible cent romeric properties of alpha-satellite DNA by introducing it into hamst er chromosomes. A large amplified region of ectopic alpha-satellite DN A was shown to direct binding of anticentromere antibodies (ACAs) and centromere protein B (CENP-B). The chromosome containing these ectopic arrays showed a high frequency of formation of anaphase bridges. Owin g to the favourable morphology of these chromosomes, we were able to d etermine that this bridging was due to delayed sister chromatid disjun ction at the location of the ectopic alpha-satellite, and not due to d e novo formation of a fully functional kinetochore. A separate hamster cell line containing large tandemly repeated amplicons including the DHFR gene also displayed similar behaviour during anaphase. These resu lts may support a role for alpha-satellite DNA in sister chromatid coh esion at centromeres. However, other repetitive DNA in favourable conf igurations appears to be capable of mimicking this behaviour during an aphase.