Within the polytene chromosomes of Drosophila, chromatin is organized into band and interband regions. These have different higher-order structures, which are thought to control expression of the genes in these regions. What establishes and maintains the differences in chromatin organization is unclear. Kristen Johansen and colleagues now report that an interband-specific complex that contains the chromodomain protein Chromator and the tandem kinase JIL-1 regulates the structure of Drosophila polytene chromosomes (see ). The authors use two new hypomorphic alleles to show that impaired Chromator function causes disorganization and misalignment of band/interband regions - this is similar but not identical to what is seen in JIL-1 mutant flies. Johansen and colleagues also show that Chromator and JIL-1 co-localize at polytene interband regions, that the two proteins interact directly through their C-terminal domains, and that this interaction is biologically significant - Drosophila that lack both proteins have reduced viability during development. The authors thus conclude that Chromator and JIL-1 interact in a multiprotein interband-specific complex that can establish and/or maintain global chromatin structure.
