Biology subjects

Veenhoff, L. M.

Publications and source records attributed to Veenhoff, L. M..

11 recordsLinked to original sources

bioRxiv2026

The chaperone Jjj2 regulates nucleoporin condensation in budding yeast

Nuclear pore complexes (NPCs) mediate nucleocytoplasmic transport through a selective permeability barrier established by nucleoporins (Nups) that contain intrinsically disordered phenylalanine-glycine (FG) repeats. Due to these domains, FG-Nups are prone to condensation, with a potential to transition into insoluble aggregates. How cells keep FG-Nups in a soluble, functional state during NPC assembly and within the native NPC remains poorly understood. Here, we identify the uncharacterized yeast J-domain protein Jjj2 as a Nup chaperone. Disrupting Jjj2 function or its interaction with Hsp70 chaperones triggers the accumulation of newly synthesized Nups in cytoplasmic condensates. Conversely, Jjj2 overexpression suppresses Nup condensation but also disrupts the NPC permeability barrier and is highly toxic. Overall, our data show that Jjj2, in concert with Hsp70, controls Nup phase state. This activity must be tightly regulated; while Jjj2 prevents condensation of newly produced Nups, its overactivity compromises nucleocytoplasmic compartmentalization.

cell biology↗

bioRxiv2026

The role of the nuclear pore complex in the stability of disease-related short tandem DNA repeats

Nuclear pore complexes (NPCs) mediate selective transport between the nucleus and the cytoplasm, but also contribute to maintaining genome stability. Mutations in NPC genes cause genome instability and sensitivity to DNA damaging agents, and DNA that is difficult to repair or replicate relocates to NPCs, including expanded CAG repeats, which are associated with several neurological diseases. Here, we show that other disease-related short tandem repeats also relocate to NPCs. Relocation depends on the NPC basket protein Nup1, but is independent of the rest of the basket. Abrogating relocation to the NPC increases rates of repeat contraction, but not expansion. By contrast, deletion of the basket component NUP60, which causes mislocalization of all other basket proteins except Nup1, results in greater genome instability without affecting relocation to NPCs. Our results show that NPC association is a general feature of disease-related short tandem repeats, and suggest that relocation to NPCs is separable from the other genome maintenance functions of the NPC basket.

cell biology↗

bioRxiv2025

Detecting Nuclear Pore Complex assembly in living cells

The formation of nuclear pore complexes (NPCs) -- vital gateways regulating nuclear-cytoplasmic transport -- is a highly orchestrated process requiring the integration of hundreds of nucleoporins into the nuclear envelope. A major challenge in studying this assembly process in living cells has been the difficulty to distinguish newly forming NPCs from their mature counterparts. Here, we present a powerful nanobody-based approach that overcomes this limitation. We demonstrate that a nanobody targeting the nucleoporin Nic96 from Saccharomyces cerevisiae selectively binds newly synthesized Nic96 subcomplexes prior to its incorporation into NPCs in vivo. Importantly, nanobody-bound Nic96 is incorporated in NPCs, and expression of the nanobody does not disrupt nuclear transport, cell growth, or lifespan, nor does it show genetic interactions with known NPC assembly surveillance pathways -- making it an ideal, non-perturbing tool to study NPC biogenesis in yeast. Illustrating the use of the Nic96 nanobody we report novel aspects of the early stages of assembly, including co-recruitment of Kap121 and VHH[Nic96] to putative assembly sites. In addition, we show local enrichment of newly synthesized nucleoporins on nuclear envelope proximal lipid droplets, including a specific subset of Pdr16- and Ldo16-positive lipid droplets near the nucleus-vacuole junction. When NPC assembly is delayed, association of Nic96 subcomplexes with lipid droplets increases. These findings illustrate how the strategy to pulse-label newly forming NPCs opens new avenues for dissecting the spatiotemporal regulation of NPC assembly and misassembly.

cell biology↗

bioRxiv2025

A tool to pulse-label yeast Nuclear Pore Complexes in imaging and biochemical experiments

Nuclear Pore Complexes (NPCs) are key gateways to the nucleus and major organizers of genome architecture. Despite their importance, it is still not fully understood how NPCs are formed and degraded. Tools to track specific NPCs over time or under stress could unlock critical insights into these questions. Here, we demonstrate that a brief pulse of expression of a previously developed nanobody against bakers yeast nucleoporin Nup84 (Nordeen et al. 2020) enables a robust, rapid, and straightforward method for pulse-labeling NPCs in both imaging and affinity purification experiments. This approach offers an alternative to permanent yet less rapid genetic fluorophore- or tag-switching techniques and provides a powerful tool for studying NPC inheritance and turnover through both microscopy and biochemical methods.

cell biology↗

bioRxiv2025

Spatial control of karyopherin binding avidity within NPC mimics revealed by designer FG-Nucleoporins

Nucleocytoplasmic transport occurs via nuclear pore complexes (NPCs), [~]40-60 nm wide pores lined with intrinsically disordered proteins that are rich in Phe-Gly motifs (FG-Nups) that form a selective barrier. Molecules larger than [~]50 kDa are increasingly blocked for transport unless they are bound to a nuclear transport receptor (NTR). How the amino acid sequence of FG-Nups contribute to this is not fully understood. Here, we present de novo designed artificial FG-Nups with a systematically varied FG-repeat spacing and charge-to-hydrophobicity ratio (C/H). Starting from a reference sequence termed NupY (with the average properties of natural yeast GLFG- Nups), we designed, synthesized, and experimentally tested a library of NupY variants using QCM-D experiments and phase separation assays. We find that the spacing between FG-motifs governs Kap95 absorption into the FG- Nup phase, while increasing C/H results in higher avidity for Kap95 due to an increased accessibility of FG-motifs. Molecular dynamics simulations of transport through NupY-coated pores show a reduced barrier function for noncohesive high-C/H-ratio variants and the highest transport selectivity for designs close to native GLFG-Nups. We postulate that a balance between entropic repulsion and enthalpic gain from multivalent Kap-FG-Nup interactions drives the spatial and temporal partitioning of Kaps in the NPC.

biophysics↗

bioRxiv2024

Imaging-Based Quantitative Assessment of Biomolecular Condensates in vitro and in Cells

The formation of biomolecular condensates contributes to intracellular compartmentalization, and plays an important role in many cellular processes. The characterization of condensates is however challenging, requiring advanced biophysical or biochemical methods that are often less suitable for in vivo studies. A particular need for easily accessible yet thorough methods that enable the characterization of condensates across different experimental systems thus remains. To address this, we present PhaseMetrics, a semi-automated FIJI-based image analysis pipeline tailored for quantifying particle properties from microscopy data. Tested using the FG-domain of yeast nucleoporin Nup100, PhaseMetrics accurately assesses particle properties across diverse experimental setups, including in vitro, Xenopus egg extracts, and cellular systems. It reliably detects changes induced by various conditions such as the presence of polyethylene glycol, 1,6-hexanediol, a salt gradient, and the molecular chaperone DNAJB6b. By enabling the accurate representation of the variability within the population and the detection of subtle changes at the single particle level, the method complements conventional biochemical assays. Combined, PhaseMetrics is an easily accessible, customizable pipeline that enables imaging-based quantitative assessment of biomolecular condensates in vitro and in cells, providing a valuable addition to the current toolbox.

biochemistry↗

bioRxiv2023

Specificity and mechanism of 1,6 hexanediol-induced disruption of nuclear transport

Selective transport through the nuclear pore complex (NPC) depends on the dynamic binding of the intrinsically disordered components of the NPC, the FG-nups, with each other and with nuclear transport receptors (NTRs). Hydrophobic interactions with the phenylalanines of FG-nups are critical for this dynamic binding. 1,6-hexanediol (1,6HD), is an aliphatic alcohol that interferes with hydrophobic interactions. Here we assessed the specificity and mechanism by which 1,6HD disrupts the permeability barrier of NPCs in live bakers yeast cells. Exposure to 1,6HD (10 min, 0-5%) leads to gradual loss of the NPC permeability. This is likely a direct effect on the nuclear transport machinery as cell viability, the pH and ATP levels in the cytosol, as well as the appearance of mitochondria, Golgi, peroxisomes, ER, vacuoles, plasma membrane, nucleolus, secretory pathway and stress granules are not notably changed. There are however effects on the cytoskeleton and Hsp104 to be noted. While 1,6HD treatment does not lead to dissociation or degradation of NPC subunits, a massive relocation of multiple NTRs from NPCs does occur. This displacement quantitatively correlates with the increased passive permeability of NPCs. The loss of NTRs and associated cargo will present a major change in the macromolecular crowding and composition and hence the physicochemical properties of the central channel. We conclude that 1,6HD provides a surprisingly specific intervention to temporarily permeate NPCs and we present evidence that the mechanism includes release of NTRs from the NPCs.

molecular biology↗

bioRxiv2022

Nuclear transport under stress phenocopies transport defects in models of C9Orf72 ALS

The nucleus is the hallmark of eukaryotic life and transport to and from the nucleus occurs through the nuclear pore complex (NPC). There is a multitude of data connecting the nuclear transport machinery - i.e. the NPCs and associated nuclear transport factors - to neurodegenerative diseases, but the mechanisms are not well understood. Using Saccharomyces cerevisiae, we systematically studied how the expression of polyPR and polyGA related to C9Orf72 amyotrophic lateral sclerosis impacts the nuclear transport machinery. We measured the abundance and localization of NPC components and transport factors, and assessed the kinetics of import and export by four transport receptors. PolyPR and polyGA cause distinct, and transport receptor dependent effects. We compared the specific changes in transport to those obtained when cells were exposed to different stress situations or mutations. This comparison showed similar patterns of transport defects in cells lacking specific NTRs and cells expressing polyPR. In contrast, polyGA expressing cells bear resemblance to stress conditions where energy maintenance is decreased. The similarity of the patterns of transport deficiencies suggests that polyPR has a direct effect on nuclear transport via NTRs, while polyGA impacts the energy state of the cell and subsequently changes transport.

cell biology↗

bioRxiv2021

A precise and general FRET-based method for monitoring structural transitions in protein self-organization

Proteins assemble into a tremendous variety of dynamic and functional structures. Sensitive measurements directly in cells with a high spatiotemporal resolution are needed to distinguish these different assemblies. Here, we demonstrate precise and continuous monitoring of cytoplasmic protein self-assemblies and their structural transitions. Intermolecular FRET with both the donor and acceptor protein at the same target protein provides high sensitivity while retaining the advantage of straightforward ratiometric imaging. We measure different assembly structures, transient intermediate states kinetics, and assembly formation resolved in space and time. Specifically, the method recapitulates that i) the mutant Huntingtin exon1 (mHttex1) protein first forms low-FRET and presumably less ordered assemblies in yeast and human cells, which develop into high-FRET aggregates, ii) the chaperone DNAJB6b prevents low-FRET mHttex1 assemblies, yet coassembles with mHttex1 aggregates, and iii) FUS condensates have mutation-dependent nanoscopic structures. FACS measurements allow assembly measurement in a high-throughput manner crucial for screening efforts, while fluorescence microscopy provides spatiotemporally-resolved measurements on the single-condensate level during a cells lifetime to assess the biological consequences. Implementation in other native or non-native proteins could provide insight into many studies involving protein condensation or aggregation.

biophysics↗

bioRxiv2019

A physicochemical roadmap of yeast replicative aging

Cellular aging is a multifactorial process that is characterized by a decline in homeostatic capacity, best described at the molecular level. Physicochemical properties such as pH and macromolecular crowding, are essential to all molecular processes in cells and require maintenance. Whether a drift in physicochemical properties contributes to the overall decline of homeostasis in aging is not known. Here we show that the cytosol of yeast cells acidifies modestly in early aging and sharply after senescence. Using a macromolecular crowding sensor optimized for long-term FRET measurements, we show the macromolecular crowding changes less in longer-lived cells in contrast to shorter-lived cells. While the average pH and crowding levels change only modestly with aging, we observe drastic changes in organellar volume, leading to crowding on the {micro}m scale, which we term organellar crowding. Our measurements provide an initial framework of physicochemical parameters of replicatively-aged yeast cells.

biophysics↗

bioRxiv2018

Age-dependent deterioration of nuclear pore assembly in mitotic cells decreases transport dynamics

Nuclear transport is facilitated by the Nuclear Pore Complex (NPC) and is essential for life in eukaryotes. The NPC is a long-lived and exceptionally large structure. We asked whether NPC function is compromised in ageing mitotic cells. By imaging of single yeast cells during ageing, we show that the abundance of several NPC components and NPC assembly factors decreases while signs of misassembled NPCs appear. Consequently, nuclear permeability decreases, resulting in decreased dynamics of transcription factor shuttling and increased nuclear compartmentalisation. In support that declining NPC quality control is important in mitotic ageing, we find that the transport kinetics observed in ageing is mimicked in an NPC assembly mutant. Additionally, the single cell life histories reveal that cells that better maintain NPC function are longer lived. We conclude that assembly and quality control of NPCs are major challenges for ageing mitotic cells.

cell biology↗