Enhanced ELL Phase Separation Is Crucial for Efficient DNA Damage Repair to Restart Transcription and Cell Survival.

During genotoxic stress, mammalian cells adapt to resume transcription after repair of damaged DNA. However, mechanisms of these adaptations leading to optimal transcriptional restart are poorly known. In this study, we show critical role of EAF1-mediated enhanced phase separation of elongation factor ELL in its interaction with DNA repair factors for efficient repair of damaged DNA and subsequent transcriptional restart. ELL protein has intrinsic ability to phase separate and form liquid condensates both in vitro and in vivo within mammalian cells. Upon association with EAF1, intrinsic phase separation ability of ELL is enhanced resulting in changes in material property of ELL●EAF1 condensates. Physiologically, upon exposure to genotoxic stress, ATM-mediated phosphorylation-dependent increased EAF1 binding leads to enhanced phase separation and changes the material property of ELL. This, in turn, causes its increased interaction with DNA-PKc and associated Ku complex components. This increased interaction is important for their optimal recruitment on chromatin and corresponding repair of damaged DNA and transcriptional restart. An EAF1 knockdown or ELL mutant that fails to show its enhanced interaction with EAF1 during DNA damage, also fails to show efficient DNA damage repair, transcriptional restart and cell survival after exposure to genotoxic stress.