A REPETITIVE DNA-SEQUENCE ASSOCIATED WITH THE CENTROMERES OF CHIRONOMUS-PALLIDIVITTATUS

A clone containing centromere-associated DNA from Chironomus pallidivittatus was obtained by microdissection-microcloning. It hybridizes to the centromeric end of one chromosome and exclusively to regions in the three remaining, metacentric chromosomes to which centromeres have previously been localized on cytological grounds. In the metacentric positions the hybridization can be assigned to thin bands. The clone contains 155bp tandem repeats and short flanking regions represented in all of the centromeres. Titration experiments show that the four centromeres together contain 200kb of 155bp repeat per genome. In a line of tissue culture cells the amounts are increased by a factor 1.5 - 2, resulting in proportionately extended arrays of tandem repeats. Each repeat contains two invertrepeats surrounding a region containing only AT base pairs, a feature with some similarity to functionally essential elements in the Saccharomyces cerevisiae centromere.