Hamster chromosomes containing amplified human alpha-satellite DNA show delayed sister chromatid separation in the absence of de novo kinetochore formation.

Abstract

The centromeres of human chromosomes contain large amounts of the tandemly repeated alpha-satellite DNA family. Previous studies have shown that integration of alpha-satellite DNA into ectopic locations in mammalian chromosomes can result in the de novo formation of several features of centromeric function. Here we further examine the possible centromeric properties of alpha-satellite DNA by introducing it into hamster chromosomes. A large amplified region of ectopic alpha-satellite DNA 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. Owing to the favourable morphology of these chromosomes, we were able to determine that this bridging was due to delayed sister chromatid disjunction at the location of the ectopic alpha-satellite, and not due to de 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 results may support a role for alpha-satellite DNA in sister chromatid cohesion at centromeres. However, other repetitive DNA in favourable configurations appears to be capable of mimicking this behaviour during anaphase.