Saito M Hess D Eglinger J Fritsch AW Kreysing M Weinert BT Choudhary C Matthias P 2019 Liquid-liquid phase separation (LLPS) of proteins containing intrinsically disordered regions (IDRs) has been proposed as a mechanism underlying the formation of membrane-less organelles. Tight regulation of IDR behavior is essential to ensure that LLPS only takes place when necessary. Here, we report that IDR acetylation/deacetylation regulates LLPS and assembly of stress granules (SGs), membrane-less organelles forming in response to stress. Acetylome analysis revealed that the RNA helicase DDX3X, an important component of SGs, is a novel substrate of the deacetylase HDAC6. The N-terminal IDR of DDX3X (IDR1) can undergo LLPS in vitro, and its acetylation at multiple lysine residues impairs the formation of liquid droplets. We also demonstrated that enhanced LLPS propensity through deacetylation of DDX3X-IDR1 by HDAC6 is necessary for SG maturation, but not initiation. Our analysis provides a mechanistic framework to understand how acetylation and deacetylation of IDRs regulate LLPS spatiotemporally, and impact membrane-less organelle formation in vivo. https://sonar.ch/global/documents/270412 eng info:eu-repo/semantics/altIdentifier/doi/10.1038/s41589-018-0180-7 info:eu-repo/semantics/altIdentifier/pmid/30531905 Nature chemical biology. - 2019 Acetylation Animals Catalytic Domain Cytoplasmic Granules DEAD-box RNA Helicases Gene Knockout Techniques Histone Deacetylase 6 Humans Intrinsically Disordered Proteins Lysine Mice Models, Theoretical Osmotic Pressure RNA Helicases Acetylation of intrinsically disordered regions regulates phase separation. http://purl.org/coar/resource_type/c_6501