What happens to a well-folded (fluorescent) protein within a nuclear bio-condensate

by Prof. Eitan Lerner

Department of Biological Chemistry, Hebrew University

at Biological and soft-matter physics

Thu, 27 Mar 2025, 12:10
Sacta-Rashi Building for Physics (54), room 207

Abstract

Fluorescent proteins (FPs) are commonly used as fluorescent reporters of the proteins coded by the gene to which the FP sequences are fused. This tool has been used to study many proteins in the cell, including proteins that appear in cellular membrane-less sub-compartments referred to as bio-condensates, some of which are formed via liquid-liquid phase separation (LLPS).

LLPS-formed bio-condensates are amongst the highest-density subcompartments in the cell, to the level in which non-specific protein-protein interactions between disordered protein regions are maximized, and proximities between proteins may lead to effects of macromolecular crowding. In this case, would its fluorescence characteristics change if an FP is genetically fused to one of the protein components of an LLPS-based bio-condensate?

In this talk, I will present my work on such effects on monomeric red fluorescent proteins genetically fused to heterochromatin protein 1 (HP1), which form the basis of heterochromatin bio-condensates. Specifically, I will show that at high local molecular densities, above a given threshold, the fluorescence lifetime of the mCherry chromophore decreases, which can be used to measure the local densities at different regions of a bio-condensate. I will show the mechanism of this effect, and the ability to influence the inner chromophore spectroscopic properties by sensing the outer crowdedness. Then, I will show the use of this effect in identifying the liquid phase characteristic of HP1 bio-condensates or deviations from it, in the context of embryonic stem cell differentiation.

Created on 20-03-2025 by Feingold, Mario (mario)
Updaded on 20-03-2025 by Feingold, Mario (mario)