Biology subjects

Haller, C.

Publications and source records attributed to Haller, C..

4 recordsLinked to original sources

bioRxiv2026

Regio-selective sulfation of heparin mimicking polymers defines in vivo activity

Heparin, a naturally derived glycosaminoglycan, is the most commonly used anti-thromboembolic in the world. However, the biological origin of heparin inherently results in batch-to-batch variability, large dispersity indexes, and potential contamination, leading to inconsistent activity and patient-dependent dose-response. As such, new synthetic anticoagulants are of keen interest, particularly those that mimic heparin while being amenable to alterations in polymer structure and composition for performance optimization. Herein, we report the strategy, synthesis, and evaluation of well-defined, regioselectively functionalized di-sulfated polyamidosaccharides (disulPASs) including exploration of the structure-function relationship of molecular weight and sulfation density on anticoagulant activity. Polymerization of an orthogonally protected y-lactam monomer via anionic ring-opening, followed by selective deprotection and sulfation reactions affords disulPAS. Similar to heparin, disulPASs elongate clotting time through the intrinsic and extrinsic pathways, showing molecular weight and dose-dependent responses in clotting time; are non-cytotoxic and non-hemolytic, partially neutralized by protamine sulfate, and unlike heparin, are not degraded by heparinases. As compared to less sulfated and randomly sulfated iterations of PAS, disulPAS performs superiorly, with in vitro and in vivo clotting activity most similar to native heparin.

bioengineering↗

bioRxiv2026

Omega stabilizes RNA polymerase condensates andcontributes to cellular fitness during acid stress

In eukaryotes, organization of the nucleolus is tightly linked to ribosomal RNA (rRNA) synthesis. External stresses, such as heat shock and acidosis, induce a transition of the nucleolus from a liquid- to solid-like state. Bacterial RNA polymerase (RNAP) condensates share similarities with the nucleolus as they colocalize with pre-rRNA synthesis and their assembly correlates with high rRNA synthesis. In addition, their organization is growth dependent, highlighted by dissolution upon nutritional stress. However, their behavior and biophysical properties during other stresses remain unknown. Here, we find that RNAP condensates persist during acid stress despite an arrest in cell growth. In contrast to fast-growth RNAP condensates, acid-stabilized RNAP condensates become insensitive to drug treatments, suggesting a change in their dynamics. We identify both passive and active mechanisms that contribute to the maintenance of RNAP condensates during acid stress: a drop in intracellular pH and the stringent response. Specifically, the omega subunit of RNAP, which contributes to (p)ppGpp binding site 1, is critical for condensate maintenance during acid stress. In contrast, we show that DksA, a major stress regulator that binds to RNAP, does not contribute to RNAP condensate stabilization. Interestingly, we find that maintenance of RNAP condensates correlates with survival during recovery from acid stress. Our work sheds light on a new aspect of bacterial stress tolerance through regulation of RNAP codensates and a new role for the omega subunit. Our data bring RNAP condensates conceptually one step closer to nucleoli.

microbiology↗

bioRxiv2025

Phosphorylation enables allosteric control of a viral condensate

In many viruses, intrinsically disordered proteins (IDPs) drive the formation of replicative organelles essential for viral production. In species A rotaviruses, the disordered protein NSP5 forms condensates in cells via liquid-liquid phase separation (LLPS). Yet the sequence diversity of NSP5 raises the question of whether condensate formation is conserved across all strains and if distinct variants employ alternative mechanisms for nucleating phase separation. Using a machine learning approach, we demonstrate that NSP5 variants differ significantly in their propensity to phase-separate. We engineered a variant incorporating amino acid signatures from strains with low LLPS tendency, which failed to phase separate in vitro yet supported the formation of replicative condensates in recombinant viruses in cells. Low-tendency LLPS strains require phosphorylation of NSP5 to nucleate phase separation, whereas high-tendency strains do not, suggesting distinct nucleation mechanisms. Furthermore, hydrogen-deuterium exchange mass spectrometry revealed a phosphorylation-driven allosteric switch between binding sites on the high-propensity variant. These findings establish that phosphorylation plays a context-dependent role in the formation of replicative organelles across diverse rotaviruses.

biophysics↗

bioRxiv2020

Resident and elicited macrophages differ in expression of their glycomes and lectins

The pleiotropic functions of macrophages in immune defense, tissue repair, and maintenance of tissue homeostasis are supported by the heterogeneity in macrophage sub-populations that differ both in ontogeny and polarization. Although glycans and lectins are integral to macrophage function, little is known about the factors governing their expression. Here we show that the cellular glycome of murine peritoneal macrophages primarily reflects developmental origin and to a lesser degree, cellular polarization. Resident macrophages were characterized by a simple glycome, predominantly consisting of core 1 O-glycans, while elicited macrophages also expressed core 2 O-glycans, along with highly branched and extended complex-type N-glycans, that exhibited a higher N-acetylneuraminic acid:N-glycolylneuraminic acid ratio. Strikingly, our analysis revealed that resident and elicited macrophages express 139 lectin genes, with differential expression of 49 lectin genes, including galectins, Siglecs, and C-type lectins. These results suggest that regulation of self-glycan-protein complexes may be central to macrophage residence and recruitment.

biochemistry↗