Characterization of two novel spindle matrix proteins in Drosophila, Chromator and Megator

Abstract

We have previously described the Drosophila protein Skeletor and proposed that it is a component of a spindle matrix, a relatively static structure proposed to help organize and stabilize the microtubule spindle during mitosis. In this study, we describe the cloning and characterization of a novel chromodomain protein, Chromator, which is an interaction partner of Skeletor. Chromator interacts with Skeletor in yeast two-hybrid assay as well as in in vitro pull down and coimmunoprecipitation experiments. Chromator colocalizes with Skeletor during metaphase on a spindle-like structure but becomes concentrated on the centrosomes and spindle midzone during telophase. A recessive lethal allele of Chromator has been identified. The polytene chromosome squashes prepared from homozygous Chomator mutant larvae demonstrate severe morphological defects. These data suggest that Chromator is an essential gene and is probably required for establishing or maintaining normal chromosome structures. Its association with Skeletor and its dynamic distribution pattern also suggest that Chromator may mediate spindle matrix' involvement in mitotic processes like the pericentrosomal microtubule organization as well as chromosome