Biology subjects

Hsu, C.-P.

Publications and source records attributed to Hsu, C.-P..

5 recordsLinked to original sources

bioRxiv2026

Data coverage and model formulation reshape quantitative interpretations of bacterial transcriptional regulation

Thermodynamic models quantitatively describe interactions between transcription machinery and bacterial promoters. Contrary to conventional understanding, model analysis by Parisutham et al. (2025) attributes transcriptional inhibition by repressors to overstabilization of the RNA polymerase-promoter complex rather than prevention of its formation. Moreover, it suggests an inverse scaling relationship between basal promoter strength and transcriptional fold change, applicable to both repressor- and activator-mediated regulation. To reevaluate findings from this study, we systematically analyze empirical data and compare its framework with conventional thermodynamic models. In contrast to the inverse scaling relationship, data across multiple sources exhibit a peaked tradeoff between basal promoter strength and fold change, underscoring the importance of broad data coverage in revealing the full pattern required for reliable model inference. Furthermore, we identify the model assumption responsible for the apparent inverse scaling and misinterpretation of regulatory mechanisms. Relaxing this assumption enables the model to capture the peaked tradeoff and yield inferences consistent with established mechanisms of transcriptional repression and activation. We further derive a mathematical solution that connects basal expression to fold change for both repressor- and activator-regulated promoters. Our results underscore the importance of broad data coverage to avoid a blind-men-and-elephant interpretation and establish basal promoter strength as a key design parameter governing transcriptional regulation.

systems biology↗

bioRxiv2025

Carborane-NHS esters as versatile reagents for amine-selective small-molecule modification, bioconjugation, and peptide-polymer assembly

Carboranes - hydrophobic, boron-rich clusters with unique structural properties - offer broad potential in materials science and biomedicine. They can mimic carbocyclic frameworks for designing advanced materials such as polymers and MOFs, and when incorporated into biomolecules, reduce local polarity while enriching boron content: a feature attractive for boron neutron capture therapy (BNCT). Here, we report the development of organic carborane reagents based on N-hydroxysuccinimide (NHS) esters serving as versatile platform for selective conjugation to amine residues, enabling functionalization of small molecules, peptides, and antibodies. We further introduce bifunctional carborane reagents bearing two NHS ester sites, which mediate inter- and intramolecular coupling as well as peptide-driven polymerization. The resulting carborane-peptide polymers, composed of fragments with distinct physicochemical features, represent a new class of hybrid materials. To demonstrate biomedical utility, therapeutic antibodies (trastuzumab, cetuximab, and daratumumab) were conjugated with these reagents, attaching up to 13 carboranes per antibody. Linker length was found to be critical for maximizing loading efficiency. nLC-MS/MS mapping of trastuzumab conjugates identified 15 preferential lysine modification sites, located outside CDR regions. Importantly, trastuzumab-carborane conjugates retained native HER2-targeting activity in BT-474 cell assays. These structures, integrating therapeutic antibody efficacy with boron delivery capability, hold promise as multimodal agents for BNCT.

biochemistry↗

bioRxiv2023

Growth-dependent concentration gradient of the oscillating Min system in Escherichia coli

The Min system contributes to the spatiotemporal regulation of division sites in Escherichia coli. The MinD and MinE proteins of this system self-organize into oscillatory waves in the form of concentration gradients. How the intracellular Min protein concentration gradients are coordinated with cell growth to achieve spatiotemporal accuracy of cell division is unknown. Here, we report that the MinD concentration gradient becomes progressively steeper as cells elongate, suggesting that the division inhibitory activity at the midcell also decreases with cell growth. Interestingly, the oscillation period appears relatively stable across different cell lengths. Similar features were found in cells under carbon stress conditions, but the gradient was even steeper, likely favoring division at shorter cell lengths. The length-dependent variation of the concentration gradient was further examined in silico using a reaction-diffusion model, which not only supported the above features, but also revealed a decrease in the midcell concentration as the shape of the gradient becomes steeper in growing cells. This growth-dependent regulation of the midcell concentration of MinD may be coupled with the FtsZ ring formation through the MinD-interacting protein MinC. We found that the variable concentration gradients occur by coordinating the reaction rates of the recruitment of MinD and MinE to the membrane and the recharging of MinD with ATP in the cytoplasm. In conclusion, this work uncovers the plasticity of MinD concentration gradients during interpolar oscillations throughout cell growth, an intrinsic property integrated during cell division.

cell biology↗

bioRxiv2021

BioSANS: A Software Package for Symbolic and Numeric Biological Simulation

Modeling biochemical systems can provide insights into behaviors that are difficult to observe or understand. It requires software, programming, and understanding of the system to build a model and study it. Softwares exist for systems biology modeling, but most support only certain types of modeling tasks. Desirable features including ease in preparing input, symbolic or analytical computation, parameter estimation, graphical user interface, and systems biology markup language (SBML) support are not seen concurrently in one software package. In this study, we developed a python-based software that supports these features, with both deterministic and stochastic propagations. The software can be used by graphical user interface, command line, or as a python import. We also developed a semi-programmable and intuitively easy topology input method for the biochemical reactions. We tested the software with semantic and stochastic SBML test cases. Tests on symbolic solution and parameter estimation were also included. The software we developed is reliable, well performing, convenient to use, and compliant with most of the SBML tests. So far it is the only systems biology software that supports symbolic, deterministic, and stochastic modeling in one package that also features parameter estimation and SBML support. This work offers a comprehensive set of tools and allows for better availability and accessibility for studying kinetics and dynamics in biochemical systems.

bioinformatics↗

bioRxiv2020

Basal leakage in oscillation: coupled transcriptional and translational control using feed-forward loops

The circadian clock is a complex system that plays many important roles in most organisms. Previously, many mathematical models have been used to sharpen our understanding of the Arabidopsis clock. However, these models are mostly dependent on transcriptional regulation, and the importance of post-translational regulation is still rarely discussed from theoretical aspects. In this study, we built a series of simplified oscillators with different regulations to study the importance of post-translational regulation (specifically, 26S proteasome degradation) in the clock system. We found that a simple transcriptional-based oscillator can already generate sustained oscillation, but the oscillation can be easily destroyed in the presence of transcriptional leakage. Coupling post-translational control with transcriptional-based oscillator in a feed-forward loop will greatly improve the robustness of the oscillator in the presence of basal leakage. Using these general models, we were able to replicate the increased variability observed in the E3 ligase mutant for both plant and mammalian clocks. With this insight, we also predict a plausible regulator of several E3 ligase genes in the plants clock. Thus, our results provide insights into and the plausible importance in coupling transcription and post-translation controls in the clock system. Author summaryFor circadian clocks, several current models had successfully captured the essential dynamic behavior of the clock system mainly with transcriptional regulation. Previous studies have shown that the 26s (1, 2) proteasome degradation controls are important in maintaining the stability of circadian rhythms. However, how the loss-of-function or over-expression mutant of this targeted degradations lead to unstable oscillation is still unclear. In this work, we investigate the importance of coupled transcriptional and post-translational feedback loop in the circadian oscillator. With general models our study indicate that the unstable behavior of degradation mutants could be caused by the increase in the basal level of the clock genes. We found that coupling a non-linear degradation control into this transcriptional based oscillator using feed-forward loop improves the robustness of the oscillator. Using this finding, we further predict some plausible regulators of Arabidopsiss E3 ligase protein such as COP1 and SINAT5. Hence, our results provide insights on the importance of coupling transcription and post-translation controls in the clock system.

systems biology↗