The Drosophila kismet gene is related to chromatin-remodeling factors and is required for both segmentation and segment identity

The Drosophila kismet gene was identified in a screen for dominant suppress ors of Polycomb, a repressor of homeotic genes. Here we show that kismet mu tations suppress the Polycomb mutant phenotype by blocking the ectopic tran scription of homeotic genes. Loss of zygotic kismet function causes homeoti c transformations similar to those associated with loss-of-function mutatio ns in the homeotic genes Sex combs reduced and Abdominal-B. kismet is also required for proper larval body segmentation. Loss of maternal kismet funct ion causes segmentation defects similar to those caused by mutations in the pair-rule gene even-skipped. The kismet gene encodes several large nuclear proteins that are ubiquitously expressed along the anterior-posterior axis . The Kismet proteins contain a domain conserved in the trithorax group pro tein Brahma and related chromatin-remodeling factors, providing further evi dence that alterations in chromatin structure are required to maintain the spatially restricted patterns of homeotic gene transcription.