Biology subjects

Niedzialkowska, E.

Publications and source records attributed to Niedzialkowska, E..

3 recordsLinked to original sources

bioRxiv2025

The atypical filament assembly underpins the inflammasome-independent functions of IFI16.

Inflammasomes trigger cell death upon sensing various intracellular maladies. These supra-structures relay upstream signals by sequentially assembling architecturally congruent filaments via their pyrin domains (PYDs). Interferon Inducible Protein 16 (IFI16) is an innate immune sensor that detects dysregulated nucleic acids. Once presumed as an inflammasome receptor due to its PYD, the role of IFI16 has been much more appreciated in other innate immune pathways such as regulating interferon production and viral replication restriction. Here, a cryo-EM structure of the filament assembled by the PYD of IFI16(PYD) shows a helical architecture distinct from inflammasome PYD filaments. In silico Rosetta interaction energy calculations suggest that the helical architecture of the IFI16PYD filament is incompatible with those assembled by the central inflammasome adaptor ASC and its interacting partners. Cellular experiments further support that IFI16 fails to interact with ASC. Together, we provide the structural basis for the inflammasome-independent functions of IFI16.

biophysics↗

bioRxiv2023

Structural Basis for the Phase Separation of the Chromosome Passenger Complex

The physical basis of phase separation is thought to consist of the same types of bonds that specify conventional macromolecular interactions yet is unsatisfyingly often referred to as fuzzy. Gaining clarity on the biogenesis of membraneless cellular compartments is one of the most demanding challenges in biology. Here, we focus on the chromosome passenger complex (CPC), that forms a chromatin body that regulates chromosome segregation in mitosis. Within the three regulatory subunits of the CPC implicated in phase separation -- a heterotrimer of INCENP, Survivin, and Borealin -- we identify the contact regions formed upon droplet formation using hydrogen/deuterium-exchange mass spectrometry (HXMS). These contact regions correspond to some of the interfaces seen between individual heterotrimers within the crystal lattice they form. A major contribution comes from specific electrostatic interactions that can be broken and reversed through initial and compensatory mutagenesis, respectively. Our findings reveal structural insight for interactions driving liquid-liquid demixing of the CPC. Moreover, we establish HXMS as an approach to define the structural basis for phase separation.

biochemistry↗

bioRxiv2022

Liquid-liquid phase separation of the chromosomal passenger complex drives parallel bundling of midzone microtubules

The spindle midzone is a dynamic structure that forms during anaphase, mediates chromosome segregation, and provides a signaling platform to position the cleavage furrow. The spindle midzone comprises two antiparallel bundles of microtubules (MTs) but the process of their formation is poorly understood. Here, we show that the Chromosomal Passenger Complex (CPC) undergoes liquid-liquid phase separation (LLPS) to generate parallel MT bundles in vitro when incubated with free tubulin and GTP. MT bundles emerge from CPC droplets with protruding minus-ends that then grow into long, tapered MT structures. During this growth, the CPC in condensates apparently reorganize to coat and bundle the resulting MT structures. CPC mutants attenuated for LLPS or MT binding prevented the generation of parallel MT bundles in vitro and reduced the number of MTs present at spindle midzones in HeLa cells. Our data uncovers a kinase-independent function of the CPC and provides models for how cells generate parallel-bundled MT structures that are important for the assembly of the mitotic spindle.

cell biology↗