Biology subjects

Wild, K.

Publications and source records attributed to Wild, K..

11 recordsLinked to original sources

bioRxiv2026

High regeneration-associated stress defines a distinct HCC subgroup with therapeutically exploitable vulnerabilities

Background: To date, no precision oncology approach has been established for HCC. Despite the diverse underlying causes, HCC development exhibits a uniform pathophysiology characterised by chronic hyper-proliferation, resulting from hepatocyte apoptosis and compensatory liver regeneration. This chronic hyper-proliferative pressure, termed regeneration stress, drives genomic instability during HCC onset, yet its therapeutic potential remains poorly explored. This study aimed to identify targetable vulnerabilities tied to regeneration stress and establish clinically applicable markers for treatment stratification. Methods: Weighted gene co-expression network analysis (WGCNA) was applied on external bulk RNA-seq datasets to define a LIVer REgeneration Stress Signature (LIVRESS). The signature was functionally validated using HCC patient-derived organoids (HCC-Org), and vulnerabilities were mapped using mid-throughput drug screening, single-molecule and single-cell assays, and multi-omic integration. Results: High LIVRESS scores, characterised by enrichment in replication, mitotic and DNA damage repair pathways, identified a subset of HCC patients with aggressive disease and poorer survival across aetiologies. HCC-Org with high LIVRESS scores displayed exquisite sensitivity to multiple inhibitors of the checkpoint kinase ATR. Although HCC-Org models exhibited a baseline reduction in replication fork speed, sensitivity to ATR inhibitor (ATRi) was decoupled from replication fork dynamics and rather linked to intrinsic mitotic instability. ATR inhibition triggers mitotic failure and apoptosis in LIVRESSHigh HCC-Org. This killing effect was significantly potentiated by combining ATRi with PARPi or WEE1i. Multi-omic integration identified KPNA2 as a surrogate biomarker of ATRi sensitivity. Conclusion: Our findings demonstrate that a subset of HCC-Org, characterised by high liver regeneration-associated stress, is vulnerable to ATRi-based therapies. By focusing on a comprehensive regenerative stress model, we establish a framework to stratify HCC patients and implement biomarker-driven, ATR-based therapies for HCC patients with advanced disease. Impact and implications: Regeneration stress is a key factor that drives genomic instability in HCC, providing a basis for the LIVRESS to identify patients dependent on ATR-mediated checkpoints. These findings reveal a conceptual shift for researchers and trialists: ATRi efficacy is decoupled from replication fork dynamics and instead leverages mitotic fragility. Practically, the LIVRESS and its IHC surrogate marker (KPNA2) offer a scalable roadmap for physicians to improve patient stratification in ATRi-based precision oncology trials. While requiring prospective validation, these results pave the way toward biomarker-driven therapies for advanced HCC.

cancer biology↗

bioRxiv2025

Cell-surface proteomic profiling identifies CD72 as a regulator of microglial tiling

Microglial tiling--the phenomenon of consistent cell-to-cell distances and non-overlapping processes--is regarded as a qualitative indicator of homeostasis, but mechanisms of microglial tiling are unknown. We used cell-surface proximity labeling and mass spectrometry to profile the microglial cell-surface proteome in an in vitro model of homeostatic glial physiology and used single-cell RNA sequencing and public databases to identify candidate cell-surface proteins that might modulate tiling. We designed an image-based functional assay which measures six morphological/spatial readouts to screen these proteins for modulation of tiling. CD72, a coreceptor to the B cell receptor that is expressed by microglia, disrupted tiling; we validated its effects in vitro and in situ in organotypic hippocampal brain slices. Phosphoproteomic studies revealed that CD72 modulates pathways associated with cell adhesion, repulsive receptors, microglial activation, and cytoskeletal organization. These results lay the groundwork for further investigation of the functional roles of tiling in homeostasis and disease.

neuroscience↗

bioRxiv2025

Prevention of Transgene Silencing During Human PluripotentStem Cell Differentiation

While high and stable transgene expression can be achieved in undifferentiated pluripotent stem cells, conventional transgene expression systems are often silenced upon differentiation. Silencing occurs with both randomly integrated transgenes, introduced via transposase or lentiviral methods, and with transgenes targeted to specific genomic sites, including at commonly used safe harbor loci. The challenge to robustly express experimental transgenes in differentiated pluripotent stem cells is a major bottleneck in the field for applications such as CRISPR screening. Here, we conducted a comparative analysis to systematically evaluate the impact of various promoters, transcriptional regulatory elements, insulators, and genomic integration sites on transgene silencing during neuronal differentiation. Our findings reveal that specific combinations of promoters and transcriptional stability elements are able to prevent transgene silencing during differentiation, whereas chromatin insulators had less impact on silencing and three novel safe harbor integration sites performed similarly to the CLYBL locus. Guided by these insights we developed the PiggyBac vector TK4, which showed complete resistance to transgene silencing across various neuronal and microglial differentiation protocols from six different pluripotent stem cell lines, as independently confirmed by seven different laboratories. This construct will be highly useful for assays requiring stable transgene expression during differentiation, and holds the potential for broad applications in various research fields.

neuroscience↗

bioRxiv2024

Structures of aberrant spliceosome intermediates on their way to disassembly

Intron removal during pre-mRNA splicing is of extraordinary complexity and its disruption causes a vast number of genetic diseases in humans1. While key steps of the canonical spliceosome cycle have been revealed by combined structure-function analyses2,3, structural information on an aberrant spliceosome committed to premature disassembly is not available. Here, we report two cryo-EM structures of post-Bact spliceosome intermediates from S. pombe primed for disassembly. We identify the DEAH-box helicase - G patch protein pair (Gih35-Gpl1, homologous to human DHX35-GPATCH1) and show how it maintains catalytic dormancy. In both structures, Gpl1 recognizes a remodeled active site introduced by an over-stabilization of the U5 loop I interaction with the 5 exon leading to a single nucleotide insertion at the 5splice site. Remodeling is communicated to the spliceosome surface and the Ntr1 complex that mediates disassembly is recruited. Our data pave the way for a targeted analysis of splicing quality control.

biochemistry↗

bioRxiv2024

Multi-protein assemblies orchestrate co-translational enzymatic processing on the human ribosome

Most nascent chains undergo rapid co-translational enzymatic processing as soon as their N-terminus becomes accessible at the ribosomal polypeptide tunnel exit (PTE). In eukaryotes, N-terminal methionine excision (NME) by Methionine Aminopeptidases (MAP1 and MAP2), and N-terminal acetylation (NTA) by N-Acetyl-Transferase A (NatA), is the most common set of subsequent modifications carried out on the ribosome. How these two enzymatic processes are coordinated in quick succession in the context of a rapidly translating ribosome has remained elusive. Here, we report that human NatA occupies a non-intrusive distal binding site on the ribosome which does not interfere with most other ribosome associated factors (RAFs). In this position, NatA can partake in a coordinated and dynamic assembly with MAP1 through a complex scaffolding function of the abundant Nascent Polypeptide Associated Complex (NAC). Alternatively, MAP2 can co-occupy the PTE with NatA in preparation for successive NME and NTA. In contrast to MAP1, MAP2 completely covers the PTE and is thus incompatible with NAC and MAP1 recruitment. Both assemblies can compile on the human ribosome independent of nascent chain substrates. Together, our structures provide the structural framework for the rapid coordinated orchestration of NME and NTA in protein biogenesis.

biochemistry↗

bioRxiv2023

Methionine aminopeptidase 2 and its autoproteolysis product have different binding sites on the ribosome

Excision of the initiator methionine is among the first co-translational processes that occur at the ribosome. While this crucial step in protein maturation is executed by two types of methionine aminopeptidases in eukaryotes (MAP1 and MAP2), additional roles in disease and translational regulation have drawn more attention to MAP2. Here, we report several cryo-EM structures of MAP2 at the 80S-ribosome. The MAP2 interaction is highly robust but can be perturbed by emerging nascent chains, which induce an adaptive tilting of the enzyme. In rotation, the MAP2-specific N-terminal extension engages in stabilizing interactions with the long rRNA expansion segment ES27L. Loss of this extension by autoproteolytic cleavage impedes the tunnel interaction, while promoting MAP2 to enter the ribosomal A-site, where it engages with crucial functional centers of translation. These findings reveal that proteolytic remodeling of MAP2 severely affects ribosome binding, and set the stage for targeted functional studies.

biochemistry↗

bioRxiv2022

Mechanistic insights into RNA surveillance by the canonical poly(A) polymerase Pla1 of the MTREC complex.

The S. pombe orthologue of the human PAXT complex, Mtl1-Red1 Core (MTREC), is an eleven-subunit complex which targets cryptic unstable transcripts (CUTs) to the nuclear RNA exosome for degradation. It encompasses the canonical poly(A) polymerase Pla1, responsible for polyadenylation of nascent RNA transcripts as part of the cleavage and polyadenylation factor (CPF/CPSF). In this study we identified and characterised the interaction between Pla1 and the MTREC complex core component Red1 and analysed the functional relevance of this interaction in vivo. Our crystal structure of the Pla1-Red1 complex showed that a 58-residue fragment in Red1 binds to the RNA recognition motif domain of Pla1 and tethers it to the MTREC complex. Structure-based Pla1-Red1 interaction mutations showed that Pla1, as part of MTREC complex, hyper-adenylates CUTs for their efficient degradation. Interestingly, the Red1-Pla1 interaction was also required for the efficient assembly of the fission yeast facultative heterochromatic islands. Together, our data suggest a complex interplay between the RNA surveillance and 3-end processing machineries.

molecular biology↗

bioRxiv2022

Structural inventory of cotranslational protein folding by the eukaryotic RAC complex

Folding of nascent chains emerging from the ribosome is a challenge in cellular protein homeostasis, which in eukaryotes is met by an Hsp70 chaperone triad directly binding at the ribosomal tunnel exit. The conserved ribosome-associated complex (RAC) consists of the non-canonical Hsp70 Ssz1 and the J-domain protein Zuotin (Zuo1), which in fungi acts together with the canonical Hsp70 protein Ssb. Here, we determined high-resolution cryo-electron microscopy structures of RAC bound to the 80S ribosome. RAC adopts two distinct conformations accommodating continuous ribosomal rotation by a flexible lever arm. The heterodimer is held together by a tight interaction between the Ssz1 substrate-binding domain (SBD) and the N-terminus of Zuo1, with additional contacts between the Ssz1 nucleotide-binding domain (NBD) and the Zuo1 J- and ZHD domains that form a rigid unit. The Zuo1 HPD-motif conserved in J-proteins is masked by the Ssz1 NBD, different from the canonical Hsp70 J-protein contact, however, allowing to position Ssb for activation by Zuo1. Our data provide the basis for understanding how RAC cooperates with Ssb at the ribosome in dynamic nascent chain interaction and protein folding.

biochemistry↗

bioRxiv2020

Ex vivo detection of SARS-CoV-2-specific CD8+ T cells: rapid induction, prolonged contraction, and formation of functional memory

CD8+ T cells are critical for the elimination and long-lasting protection of many viral infections, but their role in the current SARS-CoV-2 pandemic is unclear. Emerging data indicates that SARS-CoV-2-specific CD8+ T cells are detectable in the majority of individuals recovering from SARS-CoV-2 infection. However, optimal virus-specific epitopes, the role of pre-existing heterologous immunity as well as their kinetics and differentiation program during disease control have not been defined in detail. Here, we show that both pre-existing and newly induced SARS-CoV-2-specific CD8+ T-cell responses are potentially important determinants of immune protection in mild SARS-CoV-2 infection. In particular, our results can be summarized as follows: First, immunodominant SARS-CoV-2-specific CD8+ T-cell epitopes are targeted in the majority of individuals with convalescent SARS-CoV-2 infection. Second, MHC class I tetramer analyses revealed the emergence of phenotypically diverse and functionally competent pre-existing and newly induced SARS-CoV-2-specific memory CD8+ T cells that showed similar characteristics compared to influenza-specific CD8+ T cells. Third, SARS-CoV-2-specific CD8+ T-cell responses are more robustly detectable than antibodies against the SARS-CoV-2-spike protein. This was confirmed in a longitudinal analysis of acute-resolving infection that demonstrated rapid induction of the SARS-CoV-2-specific CD8+ T cells within a week followed by a prolonged contraction phase that outlasted the waning humoral immune response indicating that CD8+ T-cell responses might serve as a more precise correlate of antiviral immunity than antibody measurements after convalescence. Collectively, these data provide new insights into the fine specificity, heterogeneity, and dynamics of SARS-CoV-2-specific memory CD8+ T cells, potentially informing the rational development of a protective vaccine against SARS-CoV-2.

immunology↗

bioRxiv2020

tructural basis for the complex DNA binding behavior of the plant stem cell regulator WUSCHEL

Stem cells are one of the foundational evolutionary novelties that allowed the independent emergence of multicellularity in the plant and animal lineages. In plants, the homeodomain (HD) transcription factor WUSCHEL (WUS) is essential for the maintenance of stem cells in the shoot apical meristem. WUS has been reported to bind to diverse DNA motifs and to act as transcriptional activator and repressor. However, the mechanisms underlying this remarkable behavior have remained unclear. Here, we quantitatively delineate WUS binding to three divergent DNA motifs and resolve the relevant structural underpinnings. We show that WUS exhibits a strong binding preference for TGAA repeat sequences, while retaining the ability to weakly bind to TAAT elements. This behavior is attributable the formation of dimers through interactions of specific residues in the HD that stabilize WUS DNA interaction. Our results provide a mechanistic basis for dissecting WUS dependent regulatory networks in plant stem cell control.

plant biology↗

bioRxiv2019

Complexin suppresses spontaneous exocytosis by capturing the membrane-proximal regions of VAMP2 and SNAP25

The neuronal protein complexin contains multiple domains that exert both clamping and facilitatory functions to tune spontaneous and action potential triggered synaptic release. We address the clamping mechanism and show that the accessory helix of complexin arrests the assembly of the soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) complex that forms the core machinery of intracellular membrane fusion. In a reconstituted fusion assay, site- and stage-specific photo-cross-linking reveals that prior to fusion the complexin accessory helix laterally binds the membrane-proximal C-terminal ends of SNAP25 and VAMP2. Corresponding complexin interface mutants selectively increase spontaneous release of neurotransmitter in living neurons, implying that the accessory helix suppresses final zippering/assembly of the SNARE four-helix bundle by restraining VAMP2 and SNAP25.

neuroscience↗