α-satellite DNA and vector composition influence rates of human artificial chromosome formation

Human artificial chromosomes (HACs) have been proposed as a new class of potential gene transfer and gene therapy vector. HACs can be formed when bacterial cloning vectors containing a-satellite DNA are transfected into cultured human cells. We have compared the HAC-forming potential of different sequences to identify features critical to the efficiency of the process. Chromosome 17 or 21 alpha-satellite arrays are highly competent HAC-forming substrates in this assay. In contrast, a Y-chromosome-derived alpha-satellite sequence is inefficient, suggesting that centromere specification is at least partly dependent on DNA sequence. The length of the input array is also an important determinant, as reduction of the chromosome-17-based array from 80 kb to 35 kb reduced the frequency of HAC formation. In addition to the alpha-satellite component, vector composition also influenced HAC formation rates, size, and copy number. The data presented here have a significant impact on the design of future HAC vectors that have potential to be developed for therapeutic applications and as tools for investigating human chromosome structure and function.