BPCPPDYSOE21 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 9: Focus Phase Separation in Biological Systems I (joint session BP/CPP)

CPP 9.1: Talk

Tuesday, March 23, 2021, 09:00–09:20, BPc

Intranuclear Phase Separation of a Chromatin Scaffolding Protein — •Davide Michieletto¹, Mattia Marenda¹, David Zwicker², and Jan Kirschbaum² — ¹University of Edinburgh — ²Max Planck Institute for Dynamics and Self-Organization

The formation and regulation of phase separated condensates is now widely seen in vitro and cytoplasm, but far more challenging to observe and test in the cell nucleus. In this talk I will present recent work on an abundant nuclear RNA-binding protein called Scaffold Attachment Factor A, or SAF-A, that regulates chromatin decompaction at transcriptionally active loci through its interaction with RNA. Here I show that the intrinsically disordered RNA binding domain of SAFA * known as an RGG domain -- undergoes phase separation upon transcriptional inhibition and that the size of the condensates can be controlled by tuning the amount arginine/lysine residues in the RGG domain. By expressing a longer, and closer to native, SAFA domain we observe that the phase separation is suppressed. To explain our findings, we propose an equilibrium model in which a slowly diffusing RNA substrate can sequester RGG fragments; upon transcriptional inhibition the freed up fragments can undergo phase separation via weak self-interactions.