THE HETEROCHROMATIN PROTEIN-1 PREVENTS TELOMERE FUSIONS IN DROSOPHILA

HP1 (Heterochromatin protein 1) is a conserved, nonhistone chromosomal protein that is best known for its preferential binding to pericentri c heterochromatin and its role in position effect variegation in Droso phila. Using immunolocalization, we show that HP1 is a constant featur e of the telomeres of interphase polytene and mitotic chromosomes. Thi s localization does not require the presence of telomeric retrotranspo sons, since HP1 is also detected at the ends of terminally deleted chr omosomes that lack these elements. Importantly, larvae expressing redu ced or mutant versions of HP1 exhibit aberrant chromosome associations and multiple telomeric fusions in neuroblast cells, imaginal disks, a nd male meiotic cells. Taken together, these results provide evidence that HP1 plays a functional role in mediating normal telomere behavior in Drosophila.