Regensburg 2022 – wissenschaftliches Programm

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BP: Fachverband Biologische Physik

BP 8: Focus Session: Phase Separation in Biochemical Systems

BP 8.9: Vortrag

Dienstag, 6. September 2022, 12:00–12:15, H15

Regulation of chromatin microphase separation by adsorbed protein complexes — •Omar Adame-Arana, Gaurav Bajpai, Dana Lorber, Talila Volk, and Samuel A. Safran — Weizmann Institute of Science, Rehovot, Israel

The spatial arrangement of chromatin in the nucleus serves as a template for DNA transcription. Regions of chromatin that are loosely packed (active regions) are accessible to the transcription machinery and can be readily transcribed; in contrast, regions that are tightly packed are usually not transcribed (inactive regions). These two types of chromatin regions separate from the nucleoplasm and further form distinct compartments reminiscent of microphase separation. Chromatin phase separation due to self-attraction has been experimentally described in the past. But what controls the further, observed microphase separation into active and inactive chromatin regions? Here, we present a minimal theory in which the inactive regions experience poor solvent conditions (due to self-attraction,) but where the solvent quality for the active chromatin regions can be regulated by the adsorption of protein complexes. Using the theory of polymer brushes as well as Brownian dynamics simulations, we find that such adsorption leads to swelling of the active regions which in turn, decreases the thickness (in a flat geometry) or radius of curvature (in a spherical geometry) of the inactive chromatin microphase. We compare the theory with experiments to suggest that the solvent quality modulated by adsorption of protein complexes may be a key contributing factor in establishing and regulating the physical organization of the genome.