Polycomb group protein complexes exchange rapidly in living Drosophila.

摘要: Fluorescence recovery after photobleaching (FRAP) microscopy was used to determine the kinetic properties of Polycomb group (PcG) proteins in whole living Drosophila organisms (embryos) and tissues (wing imaginal discs salivary glands). PcG genes are essential higher eukaryotes responsible for maintenance spatially distinct repression developmentally important regulators such as homeotic genes. Their absence, well overexpression, causes transformations axial organization body. Although protein complexes have been isolated vitro, little is known about their stability or exact mechanism vivo. We determined translational diffusion constants proteins, dissociation residence times vivo at different developmental stages. In polytene nuclei, rate suggest heterogeneity complexes. Computer simulations with new models distributed were performed systems showing both binding equilibria, results compared our experimental data. able forward reverse complex formation. Complexes exchanged within a period 1-10 minutes, more than an order magnitude faster cell cycle time, ruling out which access transcription activators chromatin limited demonstrating that long-term primarily reflects mass-action chemical equilibria.