Biology subjects

Andrecka, J.

Publications and source records attributed to Andrecka, J..

3 recordsLinked to original sources

bioRxiv2026

Cryo-EM and single molecule visualization unravel the role of humancondensin II activation by M18BP1 in driving DNA compaction

DNA compaction by human condensin II is crucial for the correct organization of mitotic chromosomes. Mitotic activation of condensin II is a multi-layered process, controlled mainly by the opposing activity of the MCPH1 and M18BP1 proteins, acting as an interphase inhibitor and a mitotic activator, respectively. Mitotic phosphorylation favors M18BP1 binding to condensin II, resulting in effective and timely chromosome compaction. However, the molecular mechanisms underlying condensin II activation in driving DNA compaction remain uncharacterized. Combining cryo-electron microscopy with single molecule imaging we unravel the mechanism of condensin II activation by M18BP1 and elucidate their role in DNA compaction. The specific interaction with phosphorylated M18BP1 induces conformational changes in the condensin II complex, relieving an autoinhibitory conformation and thus allowing stable DNA binding and DNA compaction. Beyond the ATP-driven activity of isolated condensin II complexes on DNA, we observe the emergence of multimeric species that withstand the forces applied by optical tweezers, highlighting the contribution of condensin II protein-protein interactions to the mechanical reinforcement of mitotic chromosomes.

molecular biology↗

bioRxiv2023

Myosin-5 varies its steps along the irregular F-actin track

Molecular motors employ chemical energy to generate unidirectional mechanical output against a track. By contrast to the majority of macroscopic machines, they need to navigate a chaotic cellular environment, potential disorder in the track and Brownian motion. Nevertheless, decades of nanometer-precise optical studies suggest that myosin-5a, one of the prototypical molecular motors, takes uniform steps spanning 13 subunits (36 nm) along its F-actin track. Here, we use high-resolution interferometric scattering (iSCAT) microscopy to reveal that myosin takes strides spanning 22 to 34 actin subunits, despite walking straight along the helical actin filament. We show that cumulative angular disorder in F-actin accounts for the observed proportion of each stride length, akin to crossing a river on variably-spaced stepping stones. Electron microscopy revealed the structure of the stepping molecule. Our results indicate that both motor and track are soft materials that can adapt to function in complex cellular conditions.

biophysics↗

bioRxiv2017

Quantitative mass imaging of single molecules in solution

The cellular processes underpinning life are orchestrated by proteins and their interactions. Structural and dynamic heterogeneity, despite being key to protein and drug function, continues to pose a fundamental challenge to existing analytical and structural methodologies used to study these associations. Here, we use interferometric scattering microscopy to mass-image single biomolecules in solution with <2% mass error, up to 19-kDa resolution and 1-kDa precision. Thereby, we resolve oligomeric distributions at high dynamic range, detect small-molecule binding, and mass-image biomolecules composed not only of amino acids, but also heterogeneous species, such as lipo- and glycoproteins. These capabilities enable us to characterize the molecular mechanisms of processes as diverse as oligomeric selfassembly, glycoprotein cross-linking, amyloidogenic protein aggregation, and actin polymerization. Interferometric scattering mass spectrometry (iSCAMS) provides spatially resolved access to the dynamics of biomolecular interactions ranging from those involving small molecules to mesoscopic assemblies, one molecule at a time.

biophysics↗