Biology subjects

Rubio, V.

Publications and source records attributed to Rubio, V..

15 recordsLinked to original sources

bioRxiv2026

spatialMET: an open and scalable framework for spatial metabolomics analysis

Mass spectrometry imaging (MSI) enables spatially resolved metabolomics in intact tissue sections, but analysis remains challenging at scale. Existing MSI workflows often require users to combine multiple software tools, while others rely on proprietary vendor software that limits interoperability and reproducibility. To address these challenges, we developed spatialMET, an open-source framework that provides an end-to-end workflow for MSI analysis. spatialMET provides a unified platform for preprocessing, spatial domain detection, and visualization. Downstream analyses include differential abundance testing, spatial autocorrelation and gradient analysis, dimensionality reduction, and correlation network analysis. Spatial domain detection uses hcdist, a C-based hierarchical clustering implementation that substantially reduces runtime and memory use relative to existing R-based approaches. spatialMET can be run through an interactive R Shiny application or as a standalone command-line workflow for larger datasets or high-performance computing environments. Applied to mouse small cell lung cancer MALDI-MSI data containing 284,673 pixels, spatialMET identified tumor-associated, stromal, and adjacent lung spatial domains that aligned with matched histology. Differential abundance analysis identified 117 m/z features that differed between tumor and stromal regions, while spatial autocorrelation analyses revealed spatially structured abundance patterns. Applying spatialMET to mouse lung adenocarcinoma data from an entire lung lobe containing 338,477 pixels further demonstrated scalability and captured spatial heterogeneity across tumor and surrounding lung tissue. In summary, spatialMET provides a scalable, open-source framework for end-to-end spatial metabolomics analysis, and it is distributed as a Docker container for reproducible deployment. Source code and installation instructions are available at https://github.com/biodatalab/spatialMET.

bioinformatics↗

bioRxiv2025

EnrichMET: R Package for Integrated Pathway and Network Analysis for Metabolomics

Advances in metabolomics have significantly improved our understanding of cellular processes by enabling the identification of hundreds of metabolites in a single experiment. These developments provide valuable insights into complex metabolic networks. While efforts have been made to develop pathway enrichment analysis (PEA), existing implementation often require multiple steps, rely on web-based interfaces, or depend on R packages configuration that may affect reproducibility and ease of use. To overcome these limitations, we introduce EnrichMet, an R package for fast, flexible, and reproducible pathway enrichment analysis. EnrichMet modules support over-representation analysis of pathways, metabolite set enrichment analysis (MetSEA), and network-based pathway analysis. The package streamlines the workflow by combining curated pathway information from the Kyoto Encyclopedia of Genes and Genomics (KEGG) and employs Fishers Exact Test to identify significantly enriched pathways. Benchmark analyses show that enrichment on sample data completes in approximately 3 seconds. EnrichMet offers both a command-line and a user-friendly Shiny interface, enabling accessibility for users with or without programming experience. Through case studies on experimental metabolomics datasets, we demonstrated that EnrichMet delivers accurate and comprehensive pathway enrichment results while minimizing computational time and simplifying user interaction. Furthermore, its flexible framework supports extensions to other data types and knowledge bases beyond KEGG, as illustrated through a lipidomics case study. By unifying performance, reproducibility, usability, and visualization within a single package, EnrichMet facilitates deeper insights and promotes efficient, transparent, and reproducible research practices. Availability and implementation(https://github.com/biodatalab/enrichmet.git)

bioinformatics↗

bioRxiv2024

iModMix: Integrative Module Analysis for Multi-omics Data

SummaryIntegrative Module Analysis for Multi-omics Data (iModMix) is a biology-agnostic framework that enables the discovery of novel associations across any type of quantitative abundance data, including but not limited to transcriptomics, proteomics, and metabolomics. Instead of relying on pathway annotations or prior biological knowledge, iModMix constructs data-driven modules using graphical lasso to estimate sparse networks from omics features. These modules are summarized into eigenfeatures and correlated across datasets for horizontal integration, while preserving the distinct feature sets and interpretability of each omics type. iModMix operates directly on matrices containing expression or abundances for a wide range of features, including but not limited to genes, proteins, and metabolites. Because it does not rely on annotations (e.g., KEGG identifiers), it can seamlessly incorporate both identified and unidentified metabolites, addressing a key limitation of many existing metabolomics tools. iModMix is available as a user-friendly R Shiny application requiring no programming expertise (https://imodmix.moffitt.org), and as an R package for advanced users (https://github.com/biodatalab/iModMix). The tool includes several public and in-house datasets to illustrate its utility in identifying novel multi-omics relationships in diverse biological contexts. Availability and implementationShiny application: https://imodmix.moffitt.org. The R package and source code: https://github.com/biodatalab/iModMix.

bioinformatics↗

bioRxiv2024

Structural understanding of NtcA regulation and of its coactivation by the adaptor PII/NtcA shuttling protein PipX, which connects PII regulation with gene expression regulation

The CRP-FNR superfamily of transcriptional regulators includes the cyanobacterial master regulator NtcA, which orchestrates large responses of cyanobacteria to nitrogen scarcity. NtcA uses as allosteric activator 2-oxoglutarate (2OG), a signal of nitrogen poorness and carbon richness, and binds a coactivating protein (PipX) that shuttles between the signaling protein PII and NtcA depending on nitrogen richness, thus connecting PII signaling and gene expression regulation. Here, combining structural (X-ray crystallography of six types of crystals including NtcA complexes with DNA, 2OG and PipX), modelling and functional (EMSA and bacterial two-hybrid) studies, we clarify the reasons for the exquisite specificity for the binding of NtcA to its target DNA, its mechanisms of activation by 2OG, and its coactivation by PipX. Our crystal structures of PipX-NtcA-DNA complexes prove that PipX does not interact with DNA, although it increases NtcA-DNA contacts, and that it stabilizes the active, DNA-binding-competent conformation of NtcA. Superimposition of this complex on a very recently reported cryoEM structure of NtcA in a Transcription Activity Complex with RNA polymerase (RNAP), shows that PipX binding helps recruit RNAP by PipX interaction with RNAP, particularly with its gamma and sigma (region 4) subunits, a structural prediction supported here by bacterial two-hybrid experiments.

biochemistry↗

bioRxiv2024

Modular Fluorescent Cholesterol Naphthalimide Probes And Their Application For Cholesterol Trafficking Studies In Cells

Development of fluorescent cholesterol analogs to better understand subcellular cholesterol trafficking is of great interest for cell biology and medicine. Our approach utilizes a bifunctional 1,8-naphthalimide scaffold with a push-pull character, modified on one side with a head group and a linker on the other side connecting it to cholesterol via an ester bond. Through structure-function studies, weve explored how different substituents--linkers and head groups--affect the ability of these fluorescent cholesterol naphthalimide analogs (CNDs) to mimic natural cholesterol behavior at both molecular and cellular levels. We categorized the resulting analogs into three groups: neutral, charged, and those featuring a hydroxyl group. Each compound was assessed for its solvatochromic behavior in organic solvents and model membranes. Extensive all-atom molecular dynamics simulations helped us examine how these analogs perform in model membranes compared to cholesterol. Additionally, we investigated the partitioning of these fluorescent probes in phase-separated giant unilamellar vesicles. We evaluated the uptake and distribution of these probes within mouse fibroblast cells and astrocytes, for their subcellular distributions in lysosomes and compared that to BODIPY-cholesterol, a well-regarded fluorescent cholesterol analog. The internalization efficiency of the fluorescent probes varies in different cell types and is affected mainly by the head groups. Our results demonstrate that the modular design significantly simplifies the creation of fluorescent cholesterol probes bearing distinct spectral, biophysical, and cellular targeting features, which makes it a valuable toolkit for the investigation of subcellular distribution and trafficking of cholesterol and its derivatives.

biochemistry↗

bioRxiv2024

The structure of the R2T complex reveals a different architecture of the related HSP90 co-chaperones R2T and R2TP

Heat shock protein 90 (HSP90) is a molecular chaperone that contributes to the maturation and activation of substrates in multiple cellular pathways. Its activity is supported by various co-chaperones. One of these is R2TP, a complex of RuvBL1-RuvBL2-RPAP3-PIH1D1 in humans, which is involved in the assembly of various multiprotein complexes, including mTORC1 and Box C/D and Box H/ACA snoRNPs. Structural analyses have shown that the complex is organized around a heterohexameric ring of the ATPases RuvBL1-RuvBL2 in both yeast and humans. In addition, several R2TP-like co-chaperones have been identified in humans, such as R2T, which lacks PIH1D1, but these are less well characterized. In seed plants, there are no PIH1D1 orthologs. Here, we have identified the R2T complex of Arabidopsis and determined its cryoEM structure. R2T associates with the prefoldin-like complex in vivo and is located in the cytosolic and nuclear compartments. R2T is organized as a dodecamer of AtRuvBL1-AtRuvBL2a that forms two rings, with one AtRPAP3 anchored to each ring. AtRPAP3 has no effect on the ATPase activity of AtRuvBL1-AtRuvBL2a and binds with a different stoichiometry than that described for human R2TP. We show the interaction of AtRPAP3 with AtRuvBL2a and AtHSP90 in vivo and describe the residues involved. Taken together, our results show that AtRPAP3 recruits AtRuvBL1-AtRuvBL2a and AtHSP90 via a mechanism that is also conserved in other eukaryotes, but that R2T and R2TP co-chaperone complexes have distinct structures that also suggest differences in their functions and mechanisms.

biochemistry↗

bioRxiv2024

Plant Cleavage Factor I complex is essential for precise cleavage and polyadenylation site determination

Cleavage factor I (CFI) is a four-subunit protein complex of the pre-mRNA 3 end processing machinery in eukaryotes. In Arabidopsis, AtCFI25a, AtCFI25b, AtCFI59, and AtCFI68 have been identified as potential components of AtCFI, in silico. Here, we show that the AtCFI25a, AtCFI59, and AtCFI68 proteins each pulled down all components of the CFI, confirming that these subunits form the plant CFI complex. Furthermore, either AtCFI59 or AtCFI68 was essential for nuclear localization of the smallest subunit, AtCFI25a. Mutants with single loss-of-function for AtCFI59 or AtCFI68 showed no obvious morphological defects compared to wild-type plants, while the double mutant displayed pleiotropic morphological defects, identical to those previously reported for AtCFI25a loss-of-function plants. Moreover, these morphological defects correlated with alterations in the usage of 3 UTR cleavage and polyadenylation sites. atcfi25a, atcfi25a atcfi25b and atcfi59 atcfi68 double mutants showed widespread changes in the choice of cleavage and polyadenylation sites. In most cases, more proximal cleavage and polyadenylation sites were used, leading to shorter 3 UTRs. In particular, genes involved in light intensity, light harvesting, photosynthesis and cold responses showed significant dependence on AtCFI function. Furthermore, transcripts coding for AtCFI subunits showed altered 3 end processing in these mutants, suggesting self-regulation function of AtCFI in plants.

molecular biology↗

bioRxiv2024

Overlapping roles of Arabidopsis INCURVATA11 and CUPULIFORMIS2 as Polycomb Repressive Complex 2 accessory proteins

Polycomb Repressive Complex 2 (PRC2) catalyzes the trimethylation of lysine 27 of histone H3 (H3K27me3) and plays a key role in epigenetic repression of gene expression in plants and animals. PRC2 core components have all been identified in Arabidopsis thaliana, with an expanding list of accessory proteins, some of which facilitate the recruitment of PRC2 to specific targets. INCURVATA11 (ICU11) is a 2-oxoglutarate and Fe2+-dependent dioxygenase that was previously shown to be a likely PRC2 accessory protein. In Tandem Affinity Purification (TAP)-based screens for interacting partners of ICU11 and its redundant paralog CUPULIFORMIS2 (CP2), we discovered that ICU11 interacts with four PRC2 core components, including EMBRYONIC FLOWER 2 (EMF2), and with the accessory proteins EMF1, TELOMERE REPEAT BINDING 1 (TRB1), TRB2, and TRB3. CP2 did not interact with PRC2 core components, nor with TRB1, TRB2, or TRB3, but did interact with TRB4 and TRB5. Both ICU11 and CP2 interacted with the nuclear proteins NAC DOMAIN CONTAINING PROTEIN 50 (NAC050), NAC052 and COP9 SIGNALOSOME SUBUNIT 1 (CSN1). Bimolecular Fluorescence Complementation (BiFC) assays revealed that ICU11 and CP2 both interact with the PRC2 core components CURLY LEAF and SWINGER, and the accessory proteins LIKE HETEROCHROMATIN PROTEIN 1, TRB1, and TRB3. ICU11 and CP2 did not interact with each other. Beyond their phenotypes, transcriptomic profiles revealed strong similarities between emf2-3 and the double mutant icu11-5 cp2-1, as well as with mutants in PRC2 core components. A significant proportion of the genes mis-regulated in icu11-5 cp2-1 are known to harbor H3K27me3 repressive marks in the wild type. Our results provide further evidence that ICU11 acts as a PRC2 accessory protein, and strongly suggest that CP2 plays a similar role.

plant biology↗

bioRxiv2024

The antioxidants esculetin and quercetin modulate differently redox balance in human NB4 leukemia cells

The aim is to study the involvement of reactive oxygen species on redox homeostasis of acute promyelocytic leukemia cells using two antioxidants as models for tentative leukemia therapies. The NB4 leukemia cell line has increased reactive oxygen species (ROS) levels. Esculetin and quercetin are antioxidants that alter redox equilibrium, diminishing cell viability and inducing cell death in some cancer cells. The analysis of the role of reactive oxygen species on redox balance and apoptosis in NB4 leukemia cells was addressed by modulating redox balance with oxidants hydrogen peroxide (H2O2) and tert-butylhydroperoxide (t-BHP) and antioxidant compounds (esculetin and quercetin). Cell viability of NB4 cells was measured by flow cytometry using propidium iodide (PI). Colorimetric MTT (3-(4, 5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) gave an index of cell metabolism. Apoptosis was measured using Annexin V-FITC (fluorescein isothiocyanate coupled to annexin V). Intracellular ROS levels were detected using the fluorescent probes H2DCFDA (2, 7-dichloro-dihydrofluorescein diacetate) and DHE (dihydro-ethidine). Pre-treatment with quercetin prevented early loss of cell viability induced by either H2O2 or t-BHP. It reduced apoptosis produced by H2O2 and prevented that induced by t-BHP. Pre-treatment with esculetin, in contrast, increased apoptosis induced by H2O2 but reduced that produced by t-BHP. The superoxide anion content increased after incubation with either H2O2 or t-BHP, mainly in esculetin pretreatment. Esculetin, but not quercetin, prevented peroxide production by either H2O2 or t-BHP. Therefore, esculetin and quercetin regulate differentially redox balance in human NB4 human leukemia cells, presumably via different redox mechanisms, which opens up potential applications in antileukemia therapy.

biochemistry↗

bioRxiv2022

The Arabidopsis ATP-Binding Cassette E protein ABCE2 is a conserved component of the translation machinery

O_LIATP-Binding Cassette E (ABCE) proteins dissociate cytoplasmic ribosomes after translation terminates, and contribute to ribosome recycling, thus linking translation termination to initiation. This function has been demonstrated to be essential in animals, fungi, and archaea, but remains unexplored in plants. C_LIO_LIIn most species, ABCE is encoded by a single-copy gene; by contrast, Arabidopsis thaliana has two ABCE paralogs, of which ABCE2 seems to conserve the ancestral function. We isolated apiculata7-1 (api7-1), a viable, hypomorphic allele of ABCE2,which has a pleiotropic morphological phenotype reminiscent of mutations affecting ribosome biogenesis factors and ribosomal proteins. We also studied api7-2, a null, recessive lethal allele of ABCE2. C_LIO_LICo-immunoprecipitation experiments showed that ABCE2 physically interacts with components of the translation machinery. An RNA-seq study of the api7-1 mutant showed increased responses to iron and sulfur starvation. We also found increased transcript levels of genes related to auxin signaling and metabolism. C_LIO_LIOur results support a conserved role for ABCE proteins in ribosome recycling in plants, as previously shown for the animal, fungal, and archaeal lineages. In plants, the ABCE2 protein seems important for general growth and vascular development, likely due to an indirect effect through auxin metabolism. C_LI

plant biology↗

bioRxiv2021

The structural role of SARS-CoV-2 genetic background in the emergence and success of spike mutations: the case of the spike A222V mutation

The S:A222V point mutation, within the G clade, was characteristic of the 20E (EU1) SARS-CoV-2 variant identified in Spain in early summer 2020. This mutation has now reappeared in the Delta subvariant AY.4.2, raising questions about its specific effect on viral infection. We report combined serological, functional, structural and computational studies characterizing the impact of this mutation. Our results reveal that S:A222V promotes an increased RBD opening and slightly increases ACE2 binding as compared to the parent S:D614G clade. Finally, S:A222V does not reduce sera neutralization capacity, suggesting it does not affect vaccine effectiveness.

molecular biology↗

bioRxiv2021

COP1 promotes seed germination by destabilizing RGA-LIKE2 (RGL2) in Arabidopsis

Under favorable moisture, temperature and light conditions, gibberellin (GA) biosynthesis is induced and triggers seed germination. A major mechanism by which GA promotes seed germination is by promoting the degradation of the DELLA protein RGL2, a major repressor of germination in Arabidopsis seeds. Analysis of seed germination phenotypes of constitutively photomorphogenic 1 (cop1) mutants and complemented COP1-OX/cop1-4 lines in response to GA and paclobutrazol (PAC) suggested a positive role for COP1 in seed germination and a relation with GA signaling. cop1-4 mutant seeds showed PAC hypersensitivity, but transformation with a COP1 overexpression construct rendered them PAC insensitive, with a phenotype similar to that of rgl2 mutant (rgl2-SK54) seeds. Furthermore, cop1-4 rgl2-SK54 double mutants showed a PAC-insensitive germination phenotype like that of rgl2-SK54, identifying COP1 as an upstream negative regulator of RGL2. COP1 interacts directly with RGL2 and in vivo this interaction is strongly enhanced by SPA1. COP1 directly ubiquitinates RGL2 to promote its degradation. Moreover, GA stabilizes COP1 with consequent RGL2 destabilization. By uncovering this COP1-RGL2 regulatory module, we reveal a novel mechanism whereby COP1 positively regulates seed germination and controls the expression of germination-promoting genes.

plant biology↗

bioRxiv2020

DET1-mediated COP1 regulation avoids HY5 activity over second-site targets to tune plant photomorphogenesis

DE-ETIOLATED1 (DET1) is a negative regulator of plant photomorphogenesis acting as a component of the C3D complex, which can further associate to CULLIN4 to form a CRL4C3D E3 ubiquitin ligase. CRL4C3D is thought to act together with CRL4COP1SPA ubiquitin ligase, to promote the ubiquitin-mediated degradation of the master regulatory transcription factor ELONGATED HYPOCOTYL5 (HY5), thereby controlling photomorphogenic gene regulatory networks. Yet, functional links between COP1 and DET1 have long remained elusive. Here, upon mass spectrometry identification of DET1 and COP1-associated proteins, we provide in vivo evidence that DET1 associates with COP1 to promote its destabilization, a process necessary to dampen HY5 protein abundance. By regulating HY5 over-accumulation, DET1 is critical to avoid its association to second-site loci, including many PIF3 target genes. Accordingly, excessive HY5 levels result in an increased HY5 repressive activity and are sufficient to trigger fusca-like phenotypes otherwise observed typically in COP1 and COP9 signalosome mutant seedlings. This study therefore identifies that DET1-mediated regulation of COP1 stability tunes down HY5 cistrome and avoids hyper-photomorphogenic responses that might compromise plant viability.

plant biology↗

bioRxiv2020

COP1 destabilizes DELLA proteins in Arabidopsis

DELLA transcriptional regulators are central components in the control of plant body form in response to the environment. This is considered to be mediated by changes in the metabolism of the hormones gibberellins (GAs), which promote the degradation of DELLAs. However, here we show that warm temperature or shade reduced the stability of a GA-insensitive DELLA allele in Arabidopsis. Furthermore, the degradation of DELLA induced by the warmth anticipated changes in GA levels and depended on the E3 ubiquitin ligase CONSTITUTIVELY PHOTOMORPHOGENIC1 (COP1). COP1 enhanced the degradation of normal and GA-insensitive DELLA alleles when co-expressed in N. benthamiana. DELLA proteins physically interacted with COP1 in yeast, mammalian and plant cells. This interaction was enhanced by the COP1 complex partner SUPRESSOR OF phyA-105 1 (SPA1). The level of ubiquitination of DELLA was enhanced by COP1 and COP1 ubiquitinated DELLA proteins in vitro. We propose that DELLAs are destabilized not only by the canonical GA-dependent pathway but also by COP1 and that this control is relevant for growth responses to shade and warm temperature. SignificanceDELLA proteins are plant-specific transcriptional regulators that act as signaling hubs at the interface between the environment and the transcriptional networks that control growth. DELLAs are destabilized by the growth-promoting hormone gibberellin, whose levels are very sensitive to environmental changes. Here we describe an alternative pathway to destabilize these proteins. We show that DELLAs are substrate of COP1, an E3 ubiquitin ligase that increases its nuclear activity to promote growth in response to shade or warmth. Our results also show that the destabilization of DELLAs by COP1 precedes the action of gibberellins, suggesting the existence of a sequential mechanism to control the stability of these proteins.

plant biology↗

bioRxiv2018

DET1-mediated degradation of a SAGA-like deubiquitination module controls H2Bub homeostasis

DE-ETIOLATED 1 (DET1) is an evolutionarily conserved component of the ubiquitination machinery that mediates the destabilization of key regulators of cell differentiation and proliferation in multicellular organisms. In this study, we provide evidence from Arabidopsis that DET1 is essential for the regulation of histone H2B monoubiquitination (H2Bub) over most genes by controlling the stability of a plant deubiquitination module (DUBm). In contrast with yeast and metazoan DUB modules that are associated with the large SAGA complex, the Arabidopsis DUBm only comprises three proteins (hereafter named SGF11, ENY2 and UBP22) and appears to act independently as a major H2Bub deubiquitinase activity. Our study further unveils that DET1-DDB1-Associated-1 (DDA1) protein interacts with SGF11 in vivo, linking the DET1 complex to light-dependent ubiquitin-mediated proteolytic degradation of the DUBm. Collectively, these findings uncover a signaling path controlling DUBm availability, potentially adjusting H2Bub turnover capacity to the cell transcriptional status.

plant biology↗