THE PRODUCT OF PROLIFERATION DISRUPTER IS CONCENTRATED AT CENTROMERESAND REQUIRED FOR MITOTIC CHROMOSOME CONDENSATION AND CELL-PROLIFERATION IN DROSOPHILA

Homozygosity for a null mutation in the proliferation disrupter (prod) gene of Drosophila causes decreased mitotic index, defects of anaphas e chromatid separation, and imperfect chromosome condensation in larva l neuroblasts and other proliferating cell populations. The defective condensation is especially obvious near the centromeres. Mutant larvae show slow growth and massive cell death in proliferating cell populat ions, followed by late larval lethality. Loss of prod function in mito tic clones leads to the arrest of oogenesis in the ovary and defective cuticle formation in imaginal disc derivatives. The prod gene encodes a novel 301-amino-acid protein that is ubiquitously expressed and hig hly concentrated at the centric heterochromatin of the second and thir d mitotic chromosomes, as well as at >400 euchromatic loci on polytene chromosomes. We propose that Prod is a nonhistone protein essential f or chromosome condensation and that the chromosomal and developmental defects are caused by incomplete centromere condensation in prod mutan ts.