Transcriptional repression and enhancer decommissioning silence cell cycle genes in postmitotic tissues: RNA-Seq Timecourse from Developing Drosophila Eye

Previous work in the developing Drosophila wing revealed that cell cycle genes are subject to two types of chromatin regulation. The majority of cell cycle genes exhibit a simple regulatory landscape, with promoters that remain accessible even after cell cycle exit. A few critical, rate-limiting cell cycle genes show a more complex and dynamic landscape, and enhancers near these genes show evidence of decomissioning after cell cycle exit has occurred. Here we address whether the findings made in the wing are applicable to other postmitotic tissues that persist for the lifetime of the animal: the eye and the brain. We find that these tissues show similar chromatin accessibility profiles at cell cycle genes, suggesting that these modes of regulation are shared across tissues and that multiple strategies support cell cycle gene repression in the postmitotic state. These include stable repression at the promoters of most cell cycle genes, combined with enhancer decommissioning at a few select, rate-limiting genes. Overall design: Gene expression was measured via RNA-Seq in Drosophila eyes at wandering third larval instar (L3), 24 hours and 44 hours after puparium formation (APF).