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bioRxiv · 10.1101/748293

Multivalent proteins rapidly and reversibly phase-separate upon osmotic cell volume change

Jalihal, A. P.·Pitchiaya, S.·Xiao, L.·Bawa, P.·Jiang, X.·Bedi, K.·Cieslik, M.·Ljungman, M.·Chinnaiyan, A. M.·Walter, N. G.
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Abstract

Processing bodies (PBs) and stress granules (SGs) are prominent examples of sub-cellular, membrane-less compartments that are observed under physiological and stress conditions, respectively. We observe that the trimeric PB protein DCP1A rapidly (within [~]10 s) phase-separates in mammalian cells during hyperosmotic stress and dissolves upon isosmotic rescue (over [~]100 s) with minimal impact on cell viability even after multiple cycles of osmotic perturbation. Strikingly, this rapid intracellular hyperosmotic phase separation (HOPS) correlates with the degree of cell volume compression, distinct from SG assembly, and is exhibited broadly by homo-multimeric (valency [≥] 2) proteins across several cell types. Notably, HOPS sequesters pre-mRNA cleavage factor components from actively transcribing genomic loci, providing a mechanism for hyperosmolarity-induced global impairment of transcription termination. Together, our data suggest that the multimeric proteome rapidly responds to changes in hydration and molecular crowding, revealing an unexpected mode of globally programmed phase separation and sequestration that adapts the cell to volume change. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=200 SRC="FIGDIR/small/748293v2_ufig1.gif" ALT="Figure 1"> View larger version (46K): org.highwire.dtl.DTLVardef@1ef81a5org.highwire.dtl.DTLVardef@1288c1eorg.highwire.dtl.DTLVardef@107355aorg.highwire.dtl.DTLVardef@3fb071_HPS_FORMAT_FIGEXP M_FIG C_FIG IN BRIEFCells constantly experience osmotic variation. These external changes lead to changes in cell volume, and consequently the internal state of molecular crowding. Here, Jalihal and Pitchiaya et al. show that multimeric proteins respond rapidly to such cellular changes by undergoing rapid and reversible phase separation. HIGHLIGHTSO_LIDCP1A undergoes rapid and reversible hyperosmotic phase separation (HOPS) C_LIO_LIHOPS of DCP1A depends on its trimerization domain C_LIO_LISelf-interacting multivalent proteins (valency [≥] 2) undergo HOPS C_LIO_LIHOPS of CPSF6 explains transcription termination defects during osmotic stress C_LI

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Jalihal, A. P., Pitchiaya, S., Xiao, L., Bawa, P., Jiang, X., Bedi, K., Cieslik, M., Ljungman, M., Chinnaiyan, A. M., Walter, N. G.. 2019-09-01. Multivalent proteins rapidly and reversibly phase-separate upon osmotic cell volume change. https://doi.org/10.1101/748293

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