Biology subjects

Storchova, Z.

Publications and source records attributed to Storchova, Z..

At least 19 recordsLinked to original sources

bioRxiv2026

Whole genome duplication uncouples cell volume scaling from mitochondrial homeostasis

Whole genome duplication, or polyploidy, increases cell size and nuclear volume, yet how cells maintain cytonuclear balance and metabolic fitness following ploidy expansion remains unclear. Using isogenic series of Saccharomyces cerevisiae strains ranging from haploid (1N) to tetraploid (4N), and isogenic human diploid and tetraploid cell lines, we investigated the impact of polyploidy on mitochondrial homeostasis and metabolic adaptation. Quantitative proteomics uncovered a sub-linear scaling of mitochondrial proteins with increasing ploidy, with pronounced depletion of respiratory chain components, mitochondrial DNA maintenance factors, and redox homeostasis proteins. These changes were highly conserved, indicating a conserved consequence of genome expansion. Impaired mitochondrial scaling reduced respiratory growth, membrane potential and oxygen consumption, and elevated oxidative stress. In budding yeast, the mitochondrial dysfunction triggered reactive oxygen species (ROS) accumulation and an unconventional activation of stress-responsive signaling pathways, including the Hog1 and cell integrity MAPK networks, which converged on Rtg2-dependent retrograde signaling to promote mitochondrial metabolism despite chronic dysfunction. Our findings identify defective mitochondrial scaling as a key consequence of polyploidy and establish ROS- and stress signaling-dependent retrograde response as a key adaptive mechanism linking genome duplication to mitochondrial homeostasis and cellular fitness.

cell biology↗

bioRxiv2026

The ribosome-associated quality control factor Vms1 protects mitochondrial import and homeostasis during translation stress

Mitochondrial protein synthesis and import are tightly coordinated to maintain cellular proteostasis, yet how cytosolic translation stress affects mitochondrial homeostasis remains poorly understood. Here, we investigated the cellular consequences of general translation stress using low-dose translation inhibitors in Saccharomyces cerevisiae. Genome-wide phenotypic screening revealed that the deletion of tRNA-hydrolase VMS1 involved in mitochondria-associated ribosomal quality control (mitoRQC) causes a unique hypersensitivity to low-dose cycloheximide. Quantitative proteomics demonstrated that translation stress triggers specific depletion of mitochondrial proteins, reduced respiratory capacity, and impaired mitochondrial membrane potential. Most notably, cytosolic translation stress strongly inhibited mitochondrial protein import, an effect that was substantially exacerbated in vms1{Delta} cells. We further identify the mitochondrial AAA-ATPase Msp1 as a protective factor during translation stress. Msp1 expression increased in vms1{Delta} cells, and its overexpression restored growth under stress, linking co-translational quality control to mitochondrial protein import surveillance. Together, our findings reveal mitochondrial protein import as a major target of cytosolic translation stress and uncover functional cooperation between mitoRQC and Msp1 in safeguarding mitochondrial proteostasis and cell survival.

cell biology↗

bioRxiv2026

Paired CRISPR screens identify mitochondrial metabolism and UBE2H as aneuploid-specific dependencies in human cancer cell lines

Aneuploidy is a hallmark of cancer and imposes widespread cellular stress, including proteotoxicity, transcriptional dysregulation, and increased metabolic demand. Although these stresses are predicted to create therapeutic vulnerabilities, the genetic dependencies of aneuploid cells remain incompletely characterized. Here, we performed paired CRISPR loss-of-function screens in isogenic aneuploid and near-euploid cancer cell line models to systematically identify aneuploidy-specific dependencies. Seven genome-wide paired screens identified ribosomes, rRNA processing, spliceosome-mediated RNA processing, proteasome subunits, and mitochondrial metabolism as top aneuploid-specific dependency gene groups. To identify therapeutically targetable aneuploid dependencies, we performed 18 additional paired CRISPR screens using a focused druggable genome library. This analysis identified the ubiquitin-conjugating enzyme UBE2H as a top aneuploid-selective dependency. Functional validation confirmed aneuploid cell dependency on UBE2H, and mechanistic analyses linked UBE2H to mitochondrial protein abundance, suggesting a role in maintaining mitochondrial proteostasis under aneuploid stress. Together, these findings define core cellular systems that support the viability of aneuploid cells and identify UBE2H as a potential therapeutic vulnerability connecting ubiquitin signaling to mitochondrial homeostasis.

cancer biology↗

bioRxiv2026

Analysis of stress-induced surfaceome remodeling reveals surface accumulation of the cation-independent mannose-6-phosphate receptor (CI-M6PR)

To ensure their survival in the face of stressors, cells have evolved stress response programs. While several transcriptional stress responses have been elucidated, little is known about the impact of stressors on membrane transport and the protein composition of the cell surface. Yet, the dynamic remodeling of the surfaceome by processes such as endocytosis is likely central for the adaptation to stress as it shapes cellular responses by influencing ion uptake and numerous signaling cascades. Indeed, we show that different stressors decrease endocytosis, thereby facilitating cellular adaptation. Using quantitative mass spectrometry, we delineate stress-specific surfaceome alterations in response to osmotic, oxidative and heat stress. Among other adaptive changes, we uncover that osmotic stress leads to a striking surface accumulation of the cation-independent mannose-6-phosphate receptor (CI-M6PR). Mechanistically, we demonstrate that osmotic stress decreases the endocytosis of CI-M6PR while upregulating its lysosomal exocytosis. These results suggest that CI-M6PR might play an important role in the cellular resilience against osmotic stress.

cell biology↗

bioRxiv2025

Mitotic BLM functions are required to maintain genomic stability

The BLM helicase is a critical genome maintenance protein involved in diverse cellular processes including DNA replication, repair, transcription, and chromosome segregation. During mitosis, it cooperates with the PICH helicase and topoisomerases to resolve ultrafine DNA bridges (UFBs) - non-chromatinized DNA structures that link sister chromatids - through a mechanism that is not yet fully understood. Here we tagged endogenous BLM and PICH with fluorescent proteins and BLM with an auxin-inducible degron to generate a cell model system that enables temporal tracking of UFB dynamics in the presence or absence of BLM. Time-resolved lattice light sheet microscopy established the dynamic localization patterns of BLM and PICH throughout the cell cycle. While BLM cycles between PML bodies and DNA repair foci in interphase, it dissociates from chromatin at the mitotic entry, and re-associates during anaphase to UFBs as well as to CENP-B-positive mitotic foci. Acute BLM depletion during mitosis increased the fraction of unresolved UFBs, micronuclei containing acentric fragments, binucleation, and resulted in subtle genomic abnormalities detected by single-cell whole genome sequencing. These findings highlight a mitosis-specific role for BLM in UFB resolution and underscore its function in preserving genomic stability. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=87 SRC="FIGDIR/small/659902v1_ufig1.gif" ALT="Figure 1"> View larger version (19K): org.highwire.dtl.DTLVardef@92d8b2org.highwire.dtl.DTLVardef@d0a915org.highwire.dtl.DTLVardef@10cac60org.highwire.dtl.DTLVardef@108da58_HPS_FORMAT_FIGEXP M_FIG C_FIG

cell biology↗

bioRxiv2025

Explainable Machine Learning Identifies Dosage Compensation Factors in Aneuploid Human Cancer Cells

Aneuploidy, a hallmark of cancer, leads to widespread changes in chromosome copy number, altering the abundance of hundreds or thousands of proteins. How-ever, evidence suggests that levels of proteins encoded on affected chromosomes are often buffered toward their abundances observed in diploid cells. Despite its preval-ence, the molecular mechanisms driving this protein dosage compensation remain largely unknown. It is unclear whether all proteins are buffered to a similar degree, what factors determine buffering, and whether dosage compensation varies across different cell lines or tumor types. Moreover, its potential adaptive advantage and therapeutic relevance remain unexplored. Here, we established a novel approach to quantify protein dosage buffering in a gene copy number-dependent manner, show-ing that dosage compensation is widespread but variable in cancer cell lines and in vivo tumor samples. By developing multifactorial machine learning models, we identify mean gene dependency, protein complex participation, haploinsufficiency, and mRNA decay as key predictors of buffering. We also show that dosage com-pensation can affect oncogenic potential and that higher buffering correlates with reduced proteotoxic stress and increased drug resistance. These findings highlight protein dosage compensation as a crucial regulatory mechanism and a potential therapeutic target in aneuploid cancers.

cancer biology↗

bioRxiv2025

A Universal Scaling Law for Mitotic Spindles Driven by Chromosome Crowding

Cells regulate the size of their internal structures to maintain function in diverse biological settings1. The mitotic spindle, a molecular micro-machine responsible for chromosome segregation2, must scale to accommodate genomes varying in size by over 10,000-fold across eukaryotes3. Yet, how spindle biomechanics adapts to vastly different genome sizes remains unknown. Here, we uncover a universal spindle scaling law, where metaphase plate width scales with genome size following a power law with an exponent of [~]1/3. We hypothesize that chromosome crowding within the metaphase plate generates compressive forces as chromosomes push against each other, thereby determining spindle size and shape. Our experiments with altered chromosome number and mechanical properties in healthy and cancerous human and mouse cells, together with a theoretical model based on inter-chromosome pushing forces and mechanical manipulations of cells, confirm this hypothesis. Extending these insights across eukaryotes, we demonstrate that chromosome crowding predicts the observed power-law scaling. The biophysical constraint of chromosome crowding offers a mechanistic explanation for the evolution of open mitosis and mitotic cell rounding, enabling the division of larger genomes. Spindle adaptability to larger genomes may promote the proliferation of polyploid cells, driving not only tumor progression but also speciation during evolution.

biophysics↗

bioRxiv2024

Aneuploidy-induced proteostasis disruption impairsmitochondrial functions and mediates aggregation ofmitochondrial precursor proteins through SQSTM1/p62

Aberrant chromosomal content, or aneuploidy, profoundly affects cellular physiology. Even a gain of a single chromosome disrupts proteostasis due to overexpression of numerous proteins. Consequently, cells accumulate SQSTM1/p62-positive cytosolic bodies and show altered proteasomal and lysosomal activity. To elucidate the p62 interaction network in aneuploid cells, we conducted p62 immunoprecipitation and proximity labeling assays followed by mass spectrometry analysis. Our investigation revealed the enrichment of mitochondrial proteins within the cytosolic p62 interactome and proxitome in aneuploid cells, but not in the proxitome spatially confined to autophagosomes. Immunofluorescence microscopy confirmed increased colocalization of p62 with novel interactors and with mitochondrial proteins in polysomic cells. Moreover, we observed mitochondrial defects characterized by increased perinuclear clustering, reduced oxygen consumption, and reduced mitochondrial DNA abundance in polysomic cells. Furthermore, we demonstrate that polysomic cells exhibit reduced import of mitochondrial proteins and accumulation of mitochondrial precursor proteins in the cytosol. Our data suggest that proteotoxic stress induced by chromosome gains leads to the sequestration of mitochondrial precursor proteins into cytosolic p62-bodies and compromises mitochondrial function.

cell biology↗

bioRxiv2024

A priority code in presequences: mitochondrial targeting signals assign specific import characteristics to precursor proteins

The biogenesis of mitochondria relies on the import of hundreds of different precursor proteins from the cytosol. Most of these proteins are synthesized with N-terminal presequences which serve as mitochondrial targeting signals. Presequences consistently form amphipathic helices, but they considerably differ in respect to their primary structure and length. Here we show that presequences can be classified into seven different groups based on their specific features. Using a test set of different presequences, we observed that group A presequences endow precursor proteins with improved in vitro import characteristics. We developed IQ-Compete (for Import and de-Quenching Competition assay), a novel assay based on fluorescence de-quenching, to monitor the import efficiencies of mitochondrial precursors in vivo. With this assay, we confirmed the increased import competence of group A presequences. Using mass spectrometry, we found that the presequence of the group A protein Oxa1 specifically recruits the tetratricopeptide repeat (TPR) containing protein TOMM34 to the cytosolic precursor protein. TOMM34 apparently serves as a presequence-specific targeting factor which increases the import efficiency of a specific subset of mitochondrial precursor proteins. Our results suggest that presequences contain a protein-specific priority code that encrypts the targeting mechanism of individual mitochondrial precursor proteins.

biochemistry↗

bioRxiv2024

Proteogenomic analysis reveals adaptive strategies to alleviate the consequences of aneuploidy in cancer

Aneuploidy is prevalent in cancer and associates with fitness advantage and poor patient prognosis. Yet, experimentally induced aneuploidy initially leads to adverse effects and impaired proliferation, suggesting that cancer cells must adapt to aneuploidy. We performed in vitro evolution of cells with extra chromosomes and obtained cell lines with improved proliferation and gene expression changes congruent with changes in aneuploid cancers. Integrated analysis of cancer multi-omics data and model cells revealed increased expression of DNA replicative and repair factors, reduced genomic instability, and reduced lysosomal degradation. We identified E2F4 and FOXM1 as transcription factors required for adaptation to aneuploidy in vitro and in cancers and validated this finding. The adaptation to aneuploidy also coincided with specific copy number aberrations that correlate with poor patient prognosis. Chromosomal engineering mimicking these aberrations improved aneuploid cell proliferation, while loss of previously present extra chromosome impaired it. The identified common adaptation strategies suggest replication stress, genomic instability, and lysosomal stress as common liabilities of aneuploid cancers.

genetics↗

bioRxiv2022

MitoStores: Chaperone-controlled protein granules store mitochondrial precursors in the cytosol

Hundreds of mitochondrial precursor proteins are synthesized in the cytosol and imported into mitochondria in a post-translational reaction. The early processes associated with mitochondrial protein targeting remain poorly understood. Here we show that in bakers yeast, the cytosol has the capacity to transiently store matrix-destined precursors in dedicated deposits which we named MitoStores. MitoStores are strongly enhanced when protein import into mitochondria is competitively inhibited by a clogging of mitochondrial import sites, but also formed under physiological conditions when cells grow on non-fermentable carbon sources. MitoStores are enriched for a specific subset of nuclear encoded mitochondrial proteins, in particular those containing N-terminal mitochondrial targeting sequences. MitoStore formation is controlled by the heat shock proteins Hsp42 and Hsp104, potentially to suppress the toxic potential of accumulating mitochondrial precursor proteins. Thus, the cytosolic protein quality control system plays an active role during early stages in mitochondrial protein targeting by the coordinated and localized sequestration of mitochondrial precursor proteins. SummaryThe yeast cytosol can deposit precursors of mitochondrial proteins in specific granules called MitoStores. MitoStores are controlled by the cytosolic chaperone system, in particular by Hsp42 and Hsp104. MitoStore formation suppresses the toxicity arising from non-imported mitochondrial precursor proteins.

biochemistry↗

bioRxiv2021

Mechanisms of genetic instability in a single S-phase following whole genome doubling

Diploid and stable karyotypes are associated with health and fitness in animals. In contrast, whole genome duplications (WGDs) - doubling full chromosome content - are linked to genetic instability (GIN) and frequently found in human cancers 1-3. It has been established that WGDs fuel chromosome instability through abnormal mitosis 4-8, however, the immediate consequences of tetraploidy in the first interphase are not known. This is an essential question because single WGD events such as cytokinesis failure can promote tumorigenesis 9. Here, we found that newly born tetraploid human cells undergo high rates of DNA damage during DNA replication in the first S-phase. Using DNA combing and single cell sequencing, we show that DNA replication dynamics is perturbed, generating under- and over-replicated regions. Mechanistically, we found that these defects result from the lack of protein mass scaling up at the G1/S transition, which impairs the fidelity of DNA replication. This work shows that within a single interphase, unscheduled tetraploid cells can acquire highly abnormal karyotypes. These findings provide an explanation for the GIN landscape that favors tumorigenesis after tetraploidization.

cell biology↗

bioRxiv2021

Scaling of cellular proteome with ploidy

Ploidy changes are frequent in nature and contribute to evolution, functional specialization and tumorigenesis (1,2). Analysis of model organisms of different ploidies revealed that increased ploidy leads to an increase in cell and nuclear volume, reduced proliferation (2-4), metabolic changes (5), lower fitness (6,7), and increased genomic instability (8,9), but the underlying mechanisms remain poorly understood. To investigate how the gene expression changes with cellular ploidy, we analyzed isogenic series of budding yeasts from 1N to 4N. We show that mRNA and protein abundance scales allometrically with ploidy, with tetraploid cells showing only threefold increase in proteins compared to haploids. This ploidy-specific scaling occurs via decreased rRNA and ribosomal protein abundance and reduced translation. We demonstrate that the Tor1 activity is reduced with increasing ploidy, which leads to rRNA gene repression via a novel Tor1-Sch9-Tup1 signaling pathway. mTORC1 and S6K activity are also reduced in human tetraploid cells and the concomitant increase of the Tup1 homolog Tle1 downregulates the rDNA transcription. Our results revealed a novel conserved mTORC1-S6K-Tup1/Tle1 pathway that ensures proteome remodeling in response to increased ploidy.

cell biology↗

bioRxiv2021

Whole-genome duplication shapes the aneuploidy landscape of human cancers

Aneuploidy - a hallmark of cancer - has tissue-specific recurrence patterns suggesting it plays a driving role in cancer initiation and progression. However, the contribution of aneuploidy to tumorigenesis depends on the cellular and genomic context in which it arises. Whole-genome duplication (WGD) is a common macro-evolutionary event that occurs in >25% of human tumors during the early stages of tumorigenesis. Although tumors that have undergone WGD are reported to be more permissive to aneuploidy than tumors that have not, it remains unknown whether WGD affects aneuploidy recurrence patterns in human cancers. Here we analyzed clinical tumor samples from 449 WGD- tumors and 157 WGD+ tumors across 22 tumor types. We found distinct recurrence patterns of aneuploidy in WGD- and WGD+ tumors. The relative prevalence of recurrent aneuploidies decreased in WGD+ tumors, in line with increased aneuploidy tolerance. Moreover, the genetic interactions between chromosome arms differed between WGD- and WGD+ tumors, giving rise to distinct co-occurrence and mutual exclusivity aneuploidy patterns. The proportion of whole-chromosome aneuploidy vs. arm-level aneuploidy was significantly higher in WGD+ tumors, indicating distinct dominant mechanisms for aneuploidy formation in WGD- and WGD+ tumors. Human cancer cell lines successfully reproduced these WGD/aneuploidy interactions, confirming the relevance of studying this phenomenon in culture. Lastly, we induced WGD in human colon cancer cell lines, and followed aneuploidy formation in the isogenic WGD+/WGD-cells under standard or selective conditions. These experiments validated key findings from the clinical tumor analysis, and revealed a causal link between WGD and altered aneuploidy landscapes. We conclude that WGD shapes the aneuploidy landscape of human tumors, and propose that the interaction between WGD and aneuploidy is a major contributor to tumor evolution.

cancer biology↗

bioRxiv2021

Systems approaches identify the consequences ofmonosomy in somatic human cells

Chromosome loss that results in monosomy is detrimental to viability, yet, it is frequently observed in cancers. How cancers survive with monosomy is unknown. Using p53 deficient monosomic cell lines, we found that chromosome loss impairs proliferation and genomic stability. Transcriptome and proteome analysis revealed a partial compensation of the gene dosage changes that mitigates the effects of chromosome loss. Monosomy triggers global gene expression changes that differ from the effects of trisomy. We show that ribosome biogenesis and translation were commonly downregulated in monosomic cells, likely due to haploinsufficiency of ribosomal genes. The ensuing ribosome biogenesis stress triggers the p53 pathway and G1 arrest when TP53 is reintroduced into monosomic cells. Accordingly, impaired ribosome biogenesis and p53 inactivation are associated with monosomy in cancer. Our first systematic study of monosomy in human cells explains why monosomy is so detrimental and how loss of p53 enables its incidence in cancer.

systems biology↗

bioRxiv2020

Chromosomal instability accelerates the evolution of resistance to anti-cancer therapies

Aneuploidy is a ubiquitous feature of human tumors, but the acquisition of aneuploidy is typically detrimental to cellular fitness. To investigate how aneuploidy could contribute to tumor growth, we triggered periods of chromosomal instability (CIN) in human cells and then exposed them to a variety of different culture environments. While chromosomal instability was universally detrimental under normal growth conditions, we discovered that transient CIN reproducibly accelerated the ability of cells to adapt and thrive in the presence of anti-cancer therapeutic agents. Single-cell sequencing revealed that these drug-resistant populations recurrently developed specific whole-chromosome gains and losses. We independently derived one aneuploidy that was frequently recovered in cells exposed to paclitaxel, and we found that this chromosome loss event was sufficient to decrease paclitaxel sensitivity. Finally, we demonstrated that intrinsic levels of CIN correlate with poor responses to a variety of systemic therapies in a collection of patient-derived xenografts. In total, our results show that while chromosomal instability generally antagonizes cell fitness, it also provides phenotypic plasticity to cancer cells that can allow them to adapt to diverse stressful environments. Moreover, our findings suggest that aneuploidy may function as an under-explored cause of therapy failure in human tumors.

cancer biology↗

bioRxiv2020

USP28 and SPINT2 mediate cell cycle arrest after whole genome doubling

Tetraploidy is frequent in cancer and whole genome doubling shapes the evolution of cancer genomes, thereby driving the transformation, metastasis and drug resistance. Yet, human cells usually arrest when they become tetraploid due to p53 activation that leads to CDKN1A expression, cell cycle arrest, senescence or apoptosis. To uncover the barriers that block proliferation of tetraploids, we performed an RNAi mediated genome-wide screen in a human cancer cell line. We identified 140 genes whose depletion improved survival of tetraploids and characterized in depth two of them: SPINT2 and USP28. We show that SPINT2 is a general regulator of CDKN1A, regulating its transcription via histone acetylation. By mass spectrometry and immunoprecipitation, we show that USP28 interacts with NuMA1 and affects centrosome clustering. Moreover, tetraploid cells accumulate DNA damage and loss of USP28 reduces checkpoint activation. Our results indicate three aspects that contribute to survival of tetraploid cells: i) increased mitogenic signaling and reduced expression of cell cycle inhibitors, ii) the ability to establish functional bipolar spindle, and iii) reduced DNA damage signaling.

cell biology↗

bioRxiv2020

The mitochondrial surface receptor Tom70 protects the cytosol against mitoprotein-induced stress

Most mitochondrial proteins are synthesized as precursors in the cytosol and post-translationally transported into mitochondria. The mitochondrial surface protein Tom70 acts at the interface of the cytosol and mitochondria. In vitro import experiments identified Tom70 as targeting receptor, particularly for hydrophobic carriers. Using in vivo methods and high content screens, we revisited the question of Tom70 function and considerably expanded the set of Tom70-dependent mitochondrial proteins. We demonstrate that the crucial activity of Tom70 is its ability to recruit cytosolic chaperones to the outer membrane. Indeed, tethering an unrelated chaperone-binding domain onto the mitochondrial surface complements most of the defects caused by Tom70 deletion. Tom70-mediated chaperone recruitment reduces the proteotoxicity of mitochondrial precursor proteins, in particular of hydrophobic inner membrane proteins. Thus, our work suggests that the predominant function of Tom70 is to tether cytosolic chaperones to the outer mitochondrial membrane, rather than to serve as a mitochondria-specifying targeting receptor.

cell biology↗