Biology subjects

Hsia, K.-C.

Publications and source records attributed to Hsia, K.-C..

3 recordsLinked to original sources

bioRxiv2024

An Interbacterial Cysteine Protease Toxin Inhibits Cell Growth by Targeting Type II DNA Topoisomerases GyrB and ParE

Bacteria deploy a diverse arsenal of toxic effectors to antagonize competitors, profoundly influencing the composition of microbial communities. Previous studies have identified an interbacterial toxin predicted to exhibit proteolytic activity that is broadly distributed among Gram-negative bacteria. However, the precise mechanism of intoxication remains unresolved. Here, we demonstrate that one such protease toxin from Escherichia coli, Cpe1, disrupts DNA replication and chromosome segregation by cleaving conserved sequences within the ATPase domain of type II DNA topoisomerases GyrB and ParE. This cleavage effectively inhibits topoisomerase-mediated relaxation of supercoiled DNA, resulting in impaired bacterial growth. Cpe1 belongs to the papain-like cysteine protease family and is associated with toxin delivery pathways, including the type VI secretion system and contact-dependent growth inhibition. The structure of Cpe1 in complex with its immunity protein reveals a neutralization mechanism involving competitive substrate binding rather than active site occlusion, distinguishing it from previously characterized effector-immunity pairs. Our findings unveil a unique mode of interbacterial intoxication and provide insights into how bacteria protect themselves from self-poisoning by protease toxins.

microbiology↗

bioRxiv2023

A Whole-Cell Screening Platform to Discover Cell Adhesion Molecules that Enable Programmable Bacterial Cell-Cell Adhesion

Developing programmable bacterial cell-cell adhesion is of significant interest due to its versatile applications. Current methods that rely on presenting cell adhesion molecules (CAMs) on bacterial surfaces are limited by the lack of a generalizable strategy to identify such molecules targeting bacterial membrane proteins in their natural states. Here, we introduce a whole-cell screening platform designed to discover CAMs targeting bacterial membrane proteins within a synthetic bacteria-displayed nanobody library. Leveraging the potency of the bacterial type IV secretion system--a contact-dependent DNA delivery nanomachine--we have established a positive feedback mechanism to selectively enrich for bacteria displaying nanobodies that target antigen-expressing cells. Our platform successfully identified functional CAMs capable of recognizing three distinct outer membrane proteins (TraN, OmpA, OmpC), demonstrating its efficacy in CAM discovery. This approach holds promise for engineering bacterial cell-cell adhesion, such as targeted antimicrobial interventions in the microbiome by deploying programmed inhibitor cells.

microbiology↗

bioRxiv2018

Karyopherin Kap114p regulates TATA-binding protein-mediated transcription

Gene expression is regulated by nuclear accessibility of transcription factors controlled by transport receptors and competitive inhibitors. Multiple karyopherin-{beta}s (Kap-{beta}s) facilitate nuclear import of yeast TATA-binding protein (yTBP). However, only Kap114p suppresses temperature-sensitive yTBP mutations, suggesting Kap114p executes undefined non-transport functions. We show that yTBP preferably binds Kap114p with an affinity three orders of magnitude higher than other Kap-{beta}s facilitating yTBP nuclear import. Our crystal structure of Kap114p reveals an extensively negatively-charged concave surface, accounting for high-affinity basic-protein binding. Furthermore, we biochemically demonstrate that two intra-HEAT-repeat inserts act as regulatory TBP-binding domains carried by TBP-associated factor 1 (TAF1-TAND), suppressing binding of yTBP with DNA and the transcription factor IIA. Remarkably, dual-knockout of Kap114 and TAF1-TAND in yeast synergistically suppresses cell growth. Our study reveals that Kap114p has a dual function that modulates the nuclear localization and activity of yTBP, illuminating how the nuclear transport machinery regulates yTBP-mediated transcription.

cell biology↗