Biology subjects

Hoffmann, T.

Publications and source records attributed to Hoffmann, T..

17 recordsLinked to original sources

bioRxiv2026

Glycine betaine-mediated transcriptional stimulation links its catabolism and vitamin B12 biosynthesis in Rhizobiaceae

Glycine betaine (GB) is a trimethylated ammonium compound widely used as a compatible solute, and serves as a carbon, nitrogen, and methyl group source in many members of the Rhizobiaceae. GB is critical for high-level vitamin B2 production, a cofactor synthesized exclusively by microorganisms. Vitamin B2 formation requires multiple methylation steps. In the industrial vitamin B2 production strain Pseudomonas denitrificans, GB has been shown to serve as a methyl group donor through its successive demethylation to glycine and to provide the carbon backbone for the universal porphyrin precursor 5-aminolevulinic acid. Moreover, previous proteomics studies have revealed increased levels of vitamin B2 biosynthetic enzymes in the presence of GB. However, it has remained unclear at what level of gene expression this regulation occurs. Here, using promoter-reporter fusions in the vitamin B2 overproducer Ensifer adhaerens LU2703 and in the low-producer Sinorhizobium meliloti 102F34, we demonstrate that GB activates promoters of both its own catabolic pathway and of major cob operons. Two of these operons encode the complete set of S-adenosylmethionine-dependent methyltransferases required for corrin ring biosynthesis, the foundational, rate-limiting stage in vitamin B12 production. Stimulation of cobE and cobH promoters as well as vitamin B2 production yields followed sigmoidal dose-response curves with saturation in a similar concentration range, suggesting a tight coupling between GB supply and biosynthetic output. Our findings uncover a novel regulatory layer in vitamin B2 biosynthesis and provide promoter-probe set-ups for further exploration of GB-mediated transcriptional control.

microbiology↗

bioRxiv2026

Profiling of Secondary Metabolites of Leaves of Indigenous and Introduced Grapes Collected from Hebron and Bethlehem Regions in the West Bank-Palestine.

Grape (Vitis vinifera L.) is one of the most cultivated plant species and has a long history in the Levant. Grape products, including leaves, are highly appreciated as healthy products, mainly because of their high levels of nutraceuticals. The significance of these products lies in the fact that poor diet is the primary cause of malnutrition, which is associated with severe noncommunicable diseases. Accordingly, this study aimed to profile secondary metabolites in a selection of grape genotypes from Hebron and Bethlehem regions in the West Bank-Palestine that include both indigenous and introduced genotypes. Fresh, delicate leaves from each genotype-region combination were analyzed for their content of secondary metabolites via LC-MS. The results revealed that the collection regions had a negligible impact, whereas the genotype impact was high and significant. More importantly, the secondary metabolites profiles of leaves allow for the clustering of the assessed genotypes into a few clusters, each with a specific set of metabolites that can serve as fingerprint profile. In conclusion, the results of the present study revealed the diversity of grape genotypes at the metabolomics level, which will help preserve indigenous grape genotypes and aid in the development of grape varieties that can cope with the adverse impacts of climate change.

plant biology↗

bioRxiv2024

Structural and kinetic insights into tRNA promoter engagement by yeast general transcription factor TFIIIC

Transcription of tRNA genes by RNA polymerase III requires the general transcription factor IIIC (TFIIIC), which recognizes intragenic A-box and B-box DNA motifs of type II gene promoters. However, the underlying mechanism has remained elusive, in part due to missing structural information for A-box recognition. In this study, we use single-particle cryo-EM and single-molecule FRET (smFRET) to reveal structural and real-time kinetic insights into how the 520 kDa yeast TFIIIC complex engages A- and B-box DNA motifs in the context of a tRNA gene promoter. Cryo-EM structures of {tau}A and {tau}B subcomplexes bound to the A- and B-box were obtained at 3.7 and 2.5 [A] resolution, respectively, while cryo-EM single particle mapping determined the specific distance and relative orientation of the {tau}A and {tau}B subcomplexes revealing a fully engaged state of TFIIIC. smFRET experiments show that overall recruitment and residence times of TFIIIC on a tRNA gene are primarily governed by B-box recognition, while footprinting experiments suggest a key role of {tau}A and the A-box in TFIIIB and Pol III recruitment following TFIIIC recognition of type II promoters.

biochemistry↗

bioRxiv2023

The cytoplasmic phosphate level has a central regulatory role in the phosphate starvation response of Caulobacter crescentus

In bacteria, the availability of environmental inorganic phosphate is typically sensed by the conserved PhoR-PhoB two-component signal transduction pathway, which is thought to use the flux through the PstSCAB phosphate transporter as a readout of the extracellular phosphate level to control phosphate-responsive genes. While the sensing of environmental phosphate is well-investigated, the regulatory effects of cytoplasmic phosphate are unclear. Here, we disentangle the physiological and transcriptional responses of Caulobacter crescentus to changes in the environmental and cytoplasmic phosphate levels by uncoupling phosphate uptake from the activity of the PstSCAB system, using an additional, heterologously produced phosphate transporter. This approach reveals a two-pronged response of C. crescentus to phosphate limitation, in which PhoR-PhoB signaling mostly facilitates the utilization of alternative phosphate sources, whereas the cytoplasmic phosphate level controls the morphological and physiological adaptation of cells to growth under global phosphate limitation. These findings open the door to a comprehensive understanding of phosphate signaling in bacteria.

microbiology↗

bioRxiv2023

Structural insights into human TFIIIC promoter recognition

Transcription factor IIIC (TFIIIC) recruits RNA polymerase (Pol) III to most of its target genes. Recognition of intragenic A- and B-box motifs in tRNA genes by TFIIIC modules {tau}A and {tau}B is the first critical step for tRNA synthesis but is mechanistically poorly understood. Here, we report cryo-EM structures of the human 624 kDa TFIIIC complex unbound and bound to a tRNA gene. The {tau}B module recognizes the B-box via DNA shape and sequence readout through the assembly of multiple winged-helix domains. TFIIIC220 forms an integral part of both {tau}A and {tau}B connecting the two subcomplexes via a [~]550 amino acid residue flexible linker. Our data provide a structural mechanism by which high-affinity B-box recognition anchors TFIIIC to promoter DNA and permits scanning for low-affinity A-boxes and TFIIIB for Pol III activation.

molecular biology↗

bioRxiv2022

Precision RNAi using synthetic shRNAmir target sites

Loss-of-function genetic tools are widely applied for validating therapeutic targets, but their utility remains limited by incomplete on- and uncontrolled off-target effects. We describe artificial RNA interference (ARTi) based on synthetic, ultra-potent, off-target-free shRNAs that enable efficient and inducible suppression of any gene upon introduction of a synthetic target sequence into non-coding transcript regions. ARTi establishes a scalable loss-of-function tool with full control over on- and off-target effects.

genetics↗

bioRxiv2022

ADGRG6 promotes adipogenesis and is involved in sex-specific fat distribution

Fat distribution differences between males and females are a major risk factor for metabolic disease, but their genetic etiology remains largely unknown. Here, we establish ADGRG6 as a major factor in adipogenesis and gender fat distribution. Deletion of ADGRG6 in human adipocytes impairs adipogenesis due to reduced cAMP signaling. Conditionally knocking out Adgrg6 in mouse adipocytes or deleting an intronic enhancer associated with gender fat distribution generates males with female-like fat deposition, which are protected against high-fat-diet-induced obesity and have improved insulin response. To showcase its therapeutic potential, we demonstrate that CRISPRi targeting of the Adgrg6 promoter or enhancer prevents high-fat-diet-induced obesity. Combined, our results associate ADGRG6 as a gender fat distribution gene and highlight its potential as a therapeutic target for metabolic disease.

genomics↗

bioRxiv2022

Evolution of a cis-acting SNP that controls Type VI Secretion in Vibrio cholerae

Mutations in regulatory mechanisms that control gene expression contribute to phenotypic diversity and thus facilitate the adaptation of microbes and other organisms to new niches. Comparative genomics can be used to infer rewiring of regulatory architecture based on large effect mutations like loss or acquisition of transcription factors but may be insufficient to identify small changes in non-coding, intergenic DNA sequence of regulatory elements that drive phenotypic divergence. In human-derived Vibrio cholerae, the response to distinct chemical cues triggers production of multiple transcription factors that can regulate the Type VI Secretion System (T6), a broadly distributed weapon for interbacterial competition. However, to date, the signaling network remains poorly understood because no regulatory element has been identified for the major T6 locus. Here we identify a conserved cis-acting single nucleotide polymorphism (SNP) controlling T6 transcription and activity. Sequence alignment of the T6 regulatory region from diverse V. cholerae strains revealed conservation of the SNP that we rewired to interconvert V. cholerae T6 activity between chitin-inducible and constitutive states. This study supports a model of pathogen evolution through a non-coding cis-regulatory mutation and preexisting, active transcription factors that confers a different fitness advantage to tightly regulated strains inside a human host and unfettered strains adapted to environmental niches. ImportanceOrganisms sense external cues with regulatory circuits that trigger the production of transcription factors, which bind specific DNA sequences at promoters ("cis" regulatory elements) to activate target genes. Mutations of transcription factors or their regulatory elements create phenotypic diversity, allowing exploitation of new niches. Waterborne pathogen Vibrio cholerae encodes the Type VI Secretion System "nanoweapon" to kill competitor cells when activated. Despite identification of several transcription factors, no regulatory element has been identified in the promoter of the major Type VI locus, to date. Combining phenotypic, genetic, and genomic analysis of diverse V. cholerae strains, we discovered a single nucleotide polymorphism in the Type VI promoter that switches its killing activity between a constitutive state beneficial outside hosts and an inducible state for constraint in a host. Our results support a role for non-coding DNA in adaptation of this pathogen.

microbiology↗

bioRxiv2022

Transglutaminase mediated asprosin oligomerization allows its tissue storage as fibers

Asprosin, the C-terminal furin cleavage product of profibrillin-1, was reported to act as a hormone that circulates at nanomolar levels and is recruited to the liver where it induces G protein-coupled activation of the cAMP-PKA pathway and stimulates rapid glucose release into the circulation. Although derived upon C-terminal cleavage of fibrillin-1, a multidomain extracellular matrix glycoprotein with a ubiquitous distribution in connective tissues, little is known about the mechanisms controlling the bioavailability of asprosin in tissues. In the current view, asprosin is mainly produced by white adipose tissue from where it is released into the blood in monomeric form. Here, by employing newly generated specific asprosin antibodies we monitored the distribution pattern of asprosin in human and murine connective tissues such as placenta, and muscle. Thereby we detected the presence of asprosin positive extracellular fibers. Further, by screening established cell lines for asprosin synthesis we found that most cells derived from musculoskeletal tissues render asprosin into an oligomerized form. Our analyses show that asprosin already multimerizes intracellularly, but that stable multimerization via covalent bonds is facilitated by transglutaminase activity. Further, asprosin fiber formation requires an intact fibrillin-1 fiber network for proper linear deposition. Our data suggest a new extracellular storage mechanism of asprosin in an oligomerized form which may regulate its cellular bioavailability in tissues.

biochemistry↗

bioRxiv2021

A Novel in vitro Model for Mature Toxoplasma gondii Bradyzoites Reveals their Metabolome and a Diminished Role of the Mitochondrial Tricarboxylic Acid Cycle

The apicomplexan parasite Toxoplasma gondii forms bradyzoite-containing tissue cysts that cause chronic and drug-tolerant infections. However, current in vitro models do not allow long-term culture of these cysts to maturity. Here, we developed a human myotube-based in vitro culture model of functionally mature tissue cysts that are orally infectious to mice and tolerate exposure to a range of antibiotics and temperature stresses. Metabolomic characterization of purified cysts reveals global changes that comprise increased levels of amino acids and decreased abundance of nucleobase- and tricarboxylic acid cycle-associated metabolites. In contrast to fast replicating tachyzoite forms of T. gondii these tissue cysts tolerate exposure to the aconitase inhibitor sodium fluoroacetate. Direct access to persistent stages of T. gondii under defined cell culture conditions will be essential for the dissection of functionally important host-parasite interactions and drug evasion mechanisms. It will also facilitate the identification of new strategies for therapeutic intervention.

microbiology↗

bioRxiv2020

Morphometry of SARS-CoV and SARS-CoV-2 particles in ultrathin sections of infected Vero cell cultures.

SARS-CoV-2 is the causative of the COVID-19 disease, which has spread pandemically around the globe within a few months. It is therefore necessary to collect fundamental information about the disease, its epidemiology and treatment, as well as about the virus itself. While the virus has been identified rapidly, detailed ultrastructural analysis of virus cell biology and architecture is still in its infancy. We therefore studied the virus morphology and morphometry of SARS-CoV-2 in comparison to SARS-CoV as it appears in Vero cell cultures by using conventional thin section electron microscopy and electron tomography. Both virus isolates, SARS-CoV Frankfurt 1 and SARS-CoV-2 Italy-INMI1, were virtually identical at the ultrastructural level and revealed a very similar particle size distribution with a median of about 100 nm without spikes. Maximal spike length of both viruses was 23 nm. The number of spikes per virus particle was about 30% higher in the SARS-CoV than in the SARS-CoV-2 isolate. This result complements a previous qualitative finding, which was related to a lower productivity of SARS-CoV-2 in cell culture in comparison to SARS-CoV.

microbiology↗

bioRxiv2020

Glycosylation of bioactive C13-apocarotenols in Nicotiana benthamiana and Mentha x piperita

C13-apocarotenoids (norisoprenoids) are carotenoid-derived oxidation products, which perform important physiological functions in plants. Although their biosynthetic pathways have been extensively studied, their metabolism including glycosylation remains elusive. Candidate uridine-diphosphate glycosyltransferase genes (UGTs) were selected for their high transcript abundance in comparison with other UGTs in vegetative tissues of Nicotiana benthamiana and Mentha x piperita, as these tissues are rich sources of apocarotenoid glucosides. Hydroxylated C13-apocarotenol substrates were produced by P450-catalyzed biotransformation and microbial/plant enzyme systems were established for the synthesis of glycosides. Natural substrates were identified by physiological aglycone libraries prepared from isolated plant glycosides. In total, we identified six UGTs that catalyze the unprecedented glucosylation of C13-apocarotenols, where glucose is bound either to the cyclohexene ring or butane side chain. MpUGT86C10 is a superior novel enzyme that catalyzes the glucosylation of allelopathic 3-hydroxy--damascone, 3-oxo--ionol, 3-oxo-7,8-dihydro--ionol (Blumenol C) and 3-hydroxy-7,8-dihydro-{beta}-ionol, while a germination test demonstrated the higher phytotoxic potential of a norisoprenoid glucoside in comparison to its aglycone. Glycosylation of C13-apocarotenoids has several functions in plants, including increased allelopathic activity of the aglycone, facilitating exudation by roots and allowing symbiosis with arbuscular mycorrhizal fungi. The results enable in-depth analyses of the roles of glycosylated norisoprenoid allelochemicals, the physiological functions of apocarotenoids during arbuscular mycorrhizal colonization and the associated maintenance of carotenoid homeostasis. One-sentence summaryWe identified six transferases in Nicotiana benthamiana and Mentha x piperita, two rich sources of glycosylated apocarotenoids that catalyze the unprecedented glycosylation of a range of hydroxylated - and {beta}-ionone/ionol derivatives and were able to modify bioactivity by glucosylation.

biochemistry↗

bioRxiv2020

The genetic architecture of fruit colour in strawberry (Fragaria x ananassa) uncovers the predominant contribution of the F. vesca subgenome to anthocyanins and reveals underlying genetic variations

Fruit colour, which is central to the sensorial and nutritional quality of the fruit, is a major breeding target in cultivated strawberry (Fragaria x ananassa). Red fruit colour is caused by the accumulation of anthocyanins, which are water-soluble flavonoids. Here, using pseudo F1 progeny derived from the cv. Capitola and the advanced line CF1116 and taking advantage of the available high density SNP array, we delineated fruit flavonoids mQTLs (13 compounds: anthocyanin, flavonols and flavan-3-ols) and colour-related QTLs (total anthocyanins and fruit colour) to narrow genomic regions corresponding to specific subgenomes of the cultivated strawberry. Findings showed that the overwhelming majority of the anthocyanin mQTLs and other colour-related QTLs are specific to F. vesca subgenome but that other subgenomes also contribute to colour variations. We then focused on two major homoeo-mQTLs for pelargonidin-3-glucoside (PgGs) localized on both male and female maps on linkage group LG3a (F. vesca subgenome). Combined high-resolution mapping of PgGs mQTLs and colour QTLs, transcriptome analysis of selected progeny individuals and whole genome sequencing of the parents led to the identification of several INDELS in the cis-regulatory region of a MYB102-like ODORANT gene and of the deletion of a putative MADS box binding motif in the 5UTR upstream region of an anthocyanidin reductase (ANR) gene, which likely underlie significant colour variations in strawberry fruit. The implications of these findings are important for the functional analysis and genetic engineering of colour-related genes and for the breeding by Marker-Assisted-Selection of new strawberry varieties with improved colour and health-benefits.

genetics↗

bioRxiv2020

Metabolite Quantitative Trait Loci for flavonoids provide new insights into the genetic architecture of strawberry (Fragaria x ananassa) fruit quality

Flavonoids are products from specialized metabolism that contribute to fruit sensorial (colour) and nutritional (antioxidant properties) quality. Here, using a pseudo full-sibling F1 progeny previously studied for fruit sensorial quality of cultivated strawberry (Fragaria x ananassa), we explored over two successive years the genetic architecture of flavonoid-related traits using LC-ESI-MS (13 compounds including anthocyanins, flavonols and flavan-3-ols) and colorimetric assays (anthocyanins, flavonoids, phenolics, FRAP and TEAC antioxidant capacity). Network correlation analysis highlighted the high connectivity of flavonoid compounds within each chemical class and low correlation with colorimetric traits except anthocyanins. Mapping onto the female and male linkage maps of 152 flavonoid metabolic QTLs (mQTLs) and of 26 colorimetric QTLs indicated co-localization on few linkage groups of major flavonoid- and taste-related QTLs previously uncovered. These results pave the way for the discovery of genetic variations underlying flavonoid mQTLs and for marker-assisted selection of strawberry varieties with improved sensorial and nutritional quality.

genetics↗

bioRxiv2019

Genetic risk score for Alzheimer's disease is associated with poor hearing

IntroductionIncipient dementia or shared genetics may partly explain the association between hearing loss and dementia. We evaluated whether genetic variants known to increase Alzheimers disease (AD) also influence hearing difficulty. MethodsUK Biobank participants aged 56+ with Caucasian genetic ancestry self-reported difficulty hearing and hearing with background noise (n=244,915) and underwent objectively measured hearing assessments (n=80,074). Poor objective hearing was defined as >-5.5 dB speech reception threshold on a Digit Triplet Test. We evaluated whether an AD genetic risk score (AD-GRS; range -1.2 to 1.9), the weighted sum of 23 previously identified AD-related polymorphisms, predicted objective or self-reported poor hearing, using age, sex, and genetic ancestry adjusted logistic regression models. ResultsHigher AD-GRS predicted objectively measured poor hearing (OR=1.06; 95% CI: 1.01, 1.11) and self-reported problems hearing with background noise (OR=1.03; 95% CI: 1.00, 1.05). DiscussionUsing novel methods, we found evidence that AD genetic risk influences hearing loss.

epidemiology↗

bioRxiv2018

Precision identification and prediction of high mortality phenotypes and disease progression pathways in severe malaria without requiring longitudinal data

The parasite Plasmodium falciparum is the main cause of severe malaria (SM). Despite treatment with antimalarial drugs, more than 450,000 SM deaths are reported every year, mainly in African children. The diversity of clinical presentations associated with SM indicate important differences in disease pathogenesis that often require specific treatment, and this clinical heterogeneity of SM is largely unresolved. In this study, we apply new machine learning and inference tools for large-scale data analysis to dissect the heterogeneity in patterns of clinical features associated with SM in 2,695 Gambian children admitted to hospital with Plasmodium falciparum malaria. This quantitative analysis, including the powerful HyperTraPS algorithm for inference of progressive processes, reveals pathways of SM symptom progression and features predicting the severity of individual patient outcomes. Notably, our approach allows the identification and dissection of disease progression pathways without the need for longitudinal observations. Learning these pathways and features from this rich dataset allows us to construct several quantitative measures of the mortality risk associated with a patient presenting with a given set of symptoms. By independently surveying expert practitioners, we show that this data-driven approach agrees with and expands the current state of knowledge on malaria progression, while simultaneously providing a data-supported framework for predicting clinical risk.

pathology↗

bioRxiv2017

Synthetic lethality between the cohesin subunits STAG1 and STAG2 in diverse cancer contexts

Recent genome analyses have identified recurrent mutations in the cohesin complex in a wide range of human cancers. Here we demonstrate that the most frequently mutated subunit of the cohesin complex, STAG2, displays a strong synthetic lethal interaction with its paralog STAG1. Mechanistically, STAG1 loss abrogates sister chromatid cohesion in STAG2 mutated but not in wild-type cells leading to mitotic catastrophe, defective cell division and apoptosis. STAG1 inactivation inhibits the proliferation of STAG2 mutated but not wild-type bladder cancer and Ewing sarcoma cell lines. Restoration of STAG2 expression in a mutated bladder cancer model alleviates the dependency on STAG1. Thus, STAG1 and STAG2 support sister chromatid cohesion to redundantly ensure cell survival. STAG1 represents a vulnerability of cancer cells carrying mutations in the major emerging tumor suppressor STAG2 across different cancer contexts. Exploiting synthetic lethal interactions to target recurrent cohesin mutations in cancer, e.g. by inhibiting STAG1, holds the promise for the development of selective therapeutics.

cancer biology↗