Biology subjects

Warnecke, T.

Publications and source records attributed to Warnecke, T..

At least 19 recordsLinked to original sources

bioRxiv2026

Single-residue variation in the nucleosome core reveals a regulatory hub for phenotypic innovation

Nucleosomes organize genomes and regulate DNA access, yet accumulating evidence suggests that their constituent histones may have functions beyond canonical chromatin regulation, but the breadth of such regulatory diversity remains unclear. Here, we used the six-residue loop 2 (L2) of H2A and H2A.Z to map, at single-residue resolution, how nucleosome-core variation reshapes cellular function. Genome-scale interaction mapping identified hundreds of regulatory connections spanning chromatin, as well as actin organization, endocytosis, and membrane trafficking. Interactions were residue-specific and differed between H2A and H2A.Z, revealing a regulatory landscape encoded by single residues. Transcriptome profiling showed limited expression changes and little overlap between differentially expressed genes and regulatory partners, indicating that non-chromatin connections are not readily explained by altered transcription. L2 substitutions also preferentially conferred benefits under cell wall and membrane stress. Thus, the nucleosome is linked to cellular-periphery functions beyond classical chromatin regulation, identifying histone variation as a source of phenotypic innovation.

molecular biology↗

bioRxiv2026

Chromatin is dispensable for bacterial life

Inside cells, DNA is intimately associated with proteins, forming chromatin. The protein constituents of chromatin vary across the tree of life: histones are the principal building blocks of chromatin in eukaryotes and many archaea, whereas bacteria typically encode a collection of nucleoid-associated proteins (NAPs) that wrap, bend, bridge or coat the DNA. Although chromatin proteins appear to be a universal feature of cellular life, DNA-templated processes such as transcription, replication, and DNA repair can take place in vitro in the absence of chromatin, raising the possibility that cellular systems might exist -- or could be built -- that lack chromatin proteins. To explore this possibility, the molecular consequences and potential systemic adjustments required for life without chromatin, we serially deleted the nine most abundant NAPs from E. coli (hupA , hupB , ihfA , ihfB , hns , stpA , fis , dps , lrp), resulting in a strain ({Delta}NAP9) that lacks its native chromatin. Using an array of different techniques, we document change -- and sometimes surprising lack thereof -- in compaction, composition and 3D architecture of the nucleoid, supercoiling, prophage activity, growth, viability, and genetic make-up of {Delta}NAP9. Most notably, we find that {Delta}NAP9 exhibits global dysregulation of gene expression, marked by a striking homogenization of transcriptional output across the genome that is reminiscent of the effects of histone depletion in eukaryotic cells. Our results reinforce the notion that chromatin plays a key role in compartmentalizing the use of genomic information, enabling both the localized suppression of selfish elements and dynamic reprogramming of genome activity in response to environmental change. At the same time, the successful construction of {Delta}NAP9 demonstrates that bacterial cells can carry out basic cellular functions in the absence of co-evolved chromatin proteins, highlighting the potential for radical (re-)engineering of prokaryotic chromatin and systems of gene expression.

microbiology↗

bioRxiv2026

Bacteriocins in archaea and archaeocins in bacteria

Archaea and bacteria routinely live side by side in microbial communities and must interact at least on occasion. Whether such cross-Domain interactions are dominated by mutual disregard, co-operation, or conflict remains fundamentally unknown. One potential window into archaeal-bacterial conflict is to ask whether some of the molecular weapons bacteria wield to kill other bacteria are present in archaea, and vice versa. Here, to start to address this question, we carry out a phylogenomic survey of bacteriocins in archaeal genomes and archaeocins in bacterial genomes. We find that more than 20% of known bacteriocins - proteins deployed by bacteria against other bacteria - have at least one homolog in archaea. Typically, these archaeal homologs are related to bacteriocins targeting (and encoded by) monoderm bacteria. Based on conservation of functionally critical residues, protein structure, and accessory genes critical for bacteriocin biosynthesis, we highlight homologs of subtilosin A, encoded in some Thermococcus archaea, as promising candidates for experimental follow- up work. We also show that halocin C8, originally described in Natrinema archaea, is comparatively common in bacterial genomes, including a number of skin-resident Staphylococcus species. Our results suggest that bacteriocins/archaeocins are shared across Domain boundaries with some regularity. While many instances are phylogenetically isolated - raising doubts about their functional importance and integration into host physiology - some bacteriocins are present in multiple related genomes and embedded in broader biosynthetic gene clusters that are also found in the original producers, suggesting that archaea and bacteria periodically use the same weapon systems in conflicts with other microbes. Further study of these systems might elucidate cross-Domain conflict and the nature of archaeal-bacterial interactions in different environments.

microbiology↗

bioRxiv2026

A Bactericidal Phospholipase from Archaea

Archaea kill bacteria, at least on occasion. The molecular underpinnings of these lethal interactions are barely understood. Here, we describe cinquedea, an /{beta} hydrolase secreted by the halophilic archaeon Haloferax larsenii s5a-1. Cinquedea exhibits bactericidal activity in the nanomolar range, killing halophilic Pontibacillus bacteria. Bacterial death is accompanied by gross morphological abnormalities, indicative of severe damage to the cell envelope. We predict, and confirm in vitro, that cinquedea is a phospholipase, with structural similarities to a phospholipase A1 enzyme isolated from hornet venom. Exposing lipids extracted from a cinquedea-sensitive Pontibacillus strain to the enzyme leads to accumulation of lysophosphatidylglycerol, a cleavage product of phospholipase A activity. This is consistent with direct activity of cinquedea against the Pontibacillus membrane, which we show is chiefly composed of phosphatidylglycerol. Considered alongside recent findings that some archaea encode bactericidal peptidoglycan hydrolases, these results suggest that archaea can kill bacteria in mechanistically diverse ways. Our work provides a template for future experimental discovery and characterization of bactericidal proteins of archaeal origin and reinforces an emerging view that archaea represent a substantial reservoir for the discovery of new antibacterial compounds.

microbiology↗

bioRxiv2025

Localised activity of reverse gyrase at gene regulatory elements

DNA topoisomerases are essential enzymes found in all cells, where they regulate DNA supercoiling. Reverse gyrase (RG) is a unique type of topoisomerase that introduces positive supercoils into DNA and appears exclusively in hyperthermophiles where it was proposed to play a key, yet still elusive, role. Here, we investigate RG activity in the hyperthermophilic archaeon Thermococcus kodakarensis at 85{degrees}C, its optimal growth temperature, using genetics and functional genomics assays. Deletion of RG led to a loss of positive supercoiling in plasmid DNA and the reduced dynamic range of transcription, without affecting histone occupancy. To investigate the effects of RG loss on the topology of chromosomal DNA, we established a psoralen photobinding assay (TMP-seq) in T. kodakarensis under native growth conditions. TMP enrichment patterns were consistent with the twin-domain model of transcription and further revealed that promoters of expressed transcription units are, on average, underwound. TMP-seq profiles in an RG deletion strain revealed that promoters are hotspots for RG activity, consistent with RG acting on hyper-negatively supercoiled substrates. We propose that RG acts not as a global modulator of supercoiling, but as a local genome guardian, selectively stabilising vulnerable regulatory regions to ensure a delicate balance between DNA accessibility and integrity under extremely high temperatures.

microbiology↗

bioRxiv2024

Systematic genome-guided discovery of antagonistic interactions between archaea and bacteria

The social life of archaea is poorly understood. In particular, even though competition and conflict are common themes in microbial communities, there is scant evidence documenting antagonistic interactions between archaea and their abundant prokaryotic brethren: bacteria. Do archaea specifically target bacteria for destruction? If so, what molecular weaponry do they use? Here, we present an approach to infer antagonistic interactions between archaea and bacteria from genome sequence. We show that a large and diverse set of archaea encode peptidoglycan hydrolases, enzymes that recognize and cleave a structure - peptidoglycan - that is a ubiquitous component of bacterial cell walls but absent from archaea. We predict the bacterial targets of archaeal peptidoglycan hydrolases using a structural homology approach and demonstrate that the predicted target bacteria tend to inhabit a similar niche to the archaeal producer, indicative of ecologically relevant interactions. Using a heterologous expression system, we demonstrate that two peptidoglycan hydrolases from the halophilic archaeaon Halogranum salarium B-1 kill the halophilic bacterium Halalkalibacterium halodurans, a predicted target, and do so in a manner consistent with peptidoglycan hydrolase activity. Our results suggest that, even though the tools and rules of engagement remain largely unknown, archaeal-bacterial conflicts are likely common, and we present a roadmap for the discovery of additional antagonistic interactions between these two domains of life. Our work has implications for understanding mixed microbial communities that include archaea and suggests that archaea might represent a large untapped reservoir of novel antibacterials.

microbiology↗

bioRxiv2024

H2A.Z and elongation factor Spt6 form an ancient bridge shaping transcription in eukaryotes

Histones are among the most conserved proteins in the eukaryotic genome, and their function is thought to be largely invariant across species. Here, we tested this assumption, examining over a billion years of the essential histone H2A.Zs evolution in a single synthetic host. We identify single residue substitutions within the H2A.Z core domain that led to its neofunctionalization. Such H2A.Z neomorphs are distinct by their ability to directly interact with the transcription apparatus, rewiring gene expression genome-wide by tuning transcription processivity. Our results reveal that even changes of single residues within the histones core domain can transform their function, catalysing the rapid emergence of phenotypic diversity by directly imposing both fitness opportunities and costs. We propose that the entire histone sequence has the potential to evolve new regulatory relationships, providing a framework to understand the mechanistic underpinnings of disease-associated histone mutations.

molecular biology↗

bioRxiv2023

Histone-organized chromatin in bacteria

Histones are the principal constituents of chromatin in eukaryotes and most archaea, while bacteria generally rely on an orthogonal set of proteins to organize their chromosomes. However, several bacterial genomes encode proteins with putative histone fold domains. Whether these proteins are structurally and functionally equivalent to archaeal and eukaryotic histones is unknown. Here, we demonstrate that histones are essential and are major components of chromatin in the bacteria Bdellovibrio bacteriovorus and Leptospira interrogans. Patterns of sequence evolution suggest important roles in several additional bacterial clades. Structural analysis of the B. bacteriovorus histone (Bd0055) dimer shows that histone fold topology is conserved between bacteria, archaea, and eukaryotes. Yet, unexpectedly, Bd0055 binds DNA end-on and forms a sheath of tightly packed histone dimers to encase straight DNA. This binding mode is in stark contrast to archaeal, eukaryotic, and viral histones, which invariably bend and wrap DNA around their outer surface. Our results demonstrate that histones are integral chromatin components across the tree of life and highlight organizational innovation in the domain Bacteria.

molecular biology↗

bioRxiv2021

Deep conservation of histone variants in Thermococcales archaea

Histones are ubiquitous in eukaryotes where they assemble into nucleosomes, binding and wrapping DNA to form chromatin. One process to modify chromatin and regulate DNA accessibility is the replacement of histones in the nucleosome with paralogous variants. Histones are also present in archaea but whether and how histone variants contribute to the generation of different physiologically relevant chromatin states in these organisms remains largely unknown. Conservation of paralogs with distinct properties can provide prima facie evidence for defined functional roles. We recently revealed deep conservation of histone paralogs with different properties in the Methanobacteriales, but little is known experimentally about these histones. In contrast, the two histones of the model archaeon Thermococcus kodakarensis, HTkA and HTkB, have been examined in some depth, both in vitro and in vivo. HTkA and HTkB exhibit distinct DNA-binding behaviours and elicit unique transcriptional responses when deleted. Here, we consider the evolution of HTkA/B and their orthologs across the order Thermococcales. We find histones with signature HTkA- and HTkB-like properties to be present in almost all Thermococcales genomes. Phylogenetic analysis indicates the presence of one HTkA- and one HTkB-like histone in the ancestor of Thermococcales and long-term maintenance of these two paralogs throughout Thermococcales diversification. Our results support the notion that archaea and eukaryotes have convergently evolved histone variants that carry out distinct adaptive functions. Intriguingly, we also detect more highly diverged histone-fold proteins, related to those found in some bacteria, in several Thermococcales genomes. The functions of these bacteria-type histones remain entirely unknown, but structural modelling suggests that they can form heterodimers with HTkA/B-like histones.

microbiology↗

bioRxiv2021

Growth temperature is the principal driver of chromatinization in archaea

Across the tree of life, DNA in living cells is associated with proteins that coat chromosomes, constrain their structure and influence DNA-templated processes such as transcription and replication. In bacteria and eukaryotes, HU and histones, respectively, are the principal constituents of chromatin, with few exceptions. Archaea, in contrast, have more diverse repertoires of nucleoid-associated proteins (NAPs). The evolutionary and ecological drivers behind this diversity are poorly understood. Here, we combine a systematic phylogenomic survey of known and predicted NAPs with quantitative protein abundance data to shed light on the forces governing the evolution of archaeal chromatin. Our survey highlights the Diaforarchaea as a hotbed of NAP innovation and turnover. Loss of histones and Alba in the ancestor of this clade was followed by multiple lineage-specific horizontal acquisitions of DNA-binding proteins from other prokaryotes. Intriguingly, we find that one family of Diaforarchaea, the Methanomethylophilaceae, lacks any known NAPs. Comparative analysis of quantitative proteomics data across a panel of 19 archaea revealed that investment in NAP production varies over two orders of magnitude, from <0.02% to >5% of total protein. Integrating genomic and ecological data, we demonstrate that growth temperature is an excellent predictor of relative NAP investment across archaea. Our results suggest that high levels of chromatinization have evolved as a mechanism to prevent uncontrolled helix opening and runaway denaturation - rather than, for example, to globally orchestrate gene expression - with implications for the origin of chromatin in both archaea and eukaryotes.

evolutionary biology↗

bioRxiv2021

Conserved Cdk inhibitors show unique structural responses to tyrosine phosphorylation

Balanced proliferation-quiescence decisions are vital during normal development and in tissue homeostasis and their dysregulation underlies tumorigenesis. Entry into proliferative cycles is driven by Cyclin/Cyclin-dependent kinases (Cdks). Conserved Cdk inhibitors (CKIs), p21Cip1/Waf1, p27Kip1 and p57Kip2, bind to Cyclin/Cdks and inhibit Cdk activity. p27 tyrosine phosphorylation, in response to mitogenic signalling, promotes activation of CyclinD/Cdk4 and CyclinA/Cdk2. Tyrosine phosphorylation is conserved in p21 and p57, although the number of sites differs. We use molecular dynamics simulations to compare the structural changes in Cyclin/Cdk/CKI trimers induced by single and multiple tyrosine phosphorylation in CKIs and their impact on CyclinD/Cdk4 and CyclinA/Cdk2 activity. Despite shared structural features, CKI binding induces distinct structural responses in Cyclin/Cdks and the predicted effects of CKI tyrosine phosphorylation on Cdk activity are not conserved across CKIs. Our analyses suggest how CKIs may have evolved to be sensitive to different inputs to give context-dependent control of Cdk activity.

cell biology↗

bioRxiv2020

Slaying the last unicorn - discovery of histones in the microalga Nanochlorum eucaryotum

Histones are the principal constituents of eukaryotic chromatin. The four core histones (H2A, H2B, H3, and H4) are conserved across sequenced eukaryotic genomes and therefore thought to be universal to eukaryotes. In the early 1980s, however, a series of biochemical investigations failed to find evidence for histones or nucleosomal structures in the microscopic green alga Nanochlorum eucaryotum. If true, derived histone loss in this lineage would constitute an exceptional case that might help us further understand the principles governing eukaryotic gene regulation. To substantiate these earlier reports of histone loss in N. eucaryotum, we sequenced, assembled and quantified its transcriptome. Following a systematic search for histone-fold domains in the assembled transcriptome, we detect orthologs to all four core histones. We also find histone mRNAs to be highly expressed, comparable to the situation in other eukaryotes. Finally, we obtain characteristic protection patterns when N. eucaryotum chromatin is subjected to micrococcal nuclease digestion, indicating widespread formation of nucleosomal complexes in vivo. We conclude that previous reports of missing histones in N. eucaryotum were mistaken. By all indications, N. eucaryotum has histone-based chromatin characteristic of most eukaryotes.

evolutionary biology↗

bioRxiv2020

Fitness landscape of a dynamic RNA structure

RNA structures are dynamic. As a consequence, mutational effects can be hard to rationalize with reference to a single static native structure. We reasoned that deep mutational scanning experiments, which couple molecular function to fitness, should capture mutational effects across multiple conformational states simultaneously. Here, we provide a proof-of-principle that this is indeed the case, using the self-splicing group I intron from Tetrahymena thermophila as a model system. We comprehensively mutagenized two 4-bp segments of the intron that come together to form the P1 extension (P1ex) helix at the 5 splice site and, following cleavage at the 5 splice site, dissociate to allow formation of an alternative helix (P10) at the 3 splice site. Using an in vivo reporter system that couples splicing activity to fitness in E. coli, we demonstrate that fitness is driven jointly by constraints on P1ex and P10 formation and that patterns of epistasis can be used to infer the presence of intramolecular pleiotropy. Importantly, using a machine learning approach that allows quantification of mutational effects in a genotype-specific manner, we show that the fitness landscape can be deconvoluted to implicate P1ex or P10 as the effective genetic background in which molecular fitness is compromised or enhanced. Our results highlight deep mutational scanning as a tool to study transient but important conformational states, with the capacity to provide critical insights into the evolution and evolvability of RNAs as dynamic ensembles. Our findings also suggest that, in the future, deep mutational scanning approaches might help us to reverse-engineer dynamic interactions and critical non-native states from a single fitness landscape.

molecular biology↗

bioRxiv2020

Histone variants in archaea and the evolution of combinatorial chromatin complexity

Nucleosomes in eukaryotes act as platforms for the dynamic integration of epigenetic information. Post-translational modifications are reversibly added or removed and core histones exchanged for paralogous variants, in concert with changing demands on transcription and genome accessibility. Histones are also common in archaea. Their role in genome regulation, however, and the capacity of individual paralogs to assemble into histone-DNA complexes with distinct properties remain poorly understood. Here, we combine structural modelling with phylogenetic analysis to shed light on archaeal histone paralogs, their evolutionary history and capacity to generate complex combinatorial chromatin states through hetero-oligomeric assembly. Focusing on the human commensal Methanosphaera stadtmanae as a model archaeal system, we show that the heteromeric complexes that can be assembled from its seven histone paralogs vary substantially in DNA binding affinity and tetramer stability, occupying a large but densely populated chromatin state space. Using molecular dynamics simulations, we go on to identify unique paralogs in M. stadtmanae and Methanobrevibacter smithii that are characterized by unstable dimer:dimer interfaces. We propose that these paralogs act as capstones that prevent stable tetramer formation and extension into longer oligomers characteristic of model archaeal histones. Importantly, we provide evidence from phylogeny and genome architecture that these capstones, as well as other paralogs in the Methanobacteriales, have been maintained for hundreds of millions of years following ancient duplication events. Taken together, our findings indicate that at least some archaeal histone paralogs have evolved to play distinct and conserved functional roles, reminiscent of eukaryotic histone variants. We conclude that combinatorially complex histone-based chromatin is not restricted to eukaryotes and likely predates their emergence.

evolutionary biology↗

bioRxiv2019

Cytosine methylation affects the mutability of neighbouring nucleotides in human, Arabidopsis, and rice

Methylated cytosines deaminate at higher rates than unmethylated cytosines and the lesions they produce are repaired less efficiently. As a result, methylated cytosines are mutational hotspots. Here, combining rare polymorphism and base-resolution methylation data in humans, Arabidopsis thaliana, and rice (Oryza sativa), we present evidence that methylation state affects mutation dynamics not only at the focal cytosine but also at neighbouring nucleotides. In humans, contrary to prior suggestions, we find that nucleotides in the close vicinity ({+/-}3nt) of methylated cytosines mutate less frequently. In contrast, methylation is associated with increased neighbourhood mutation risk in A. thaliana and rice. The difference in mutation risk associated with methylation is less pronounced further away from the focal CpG, is modulated by regional GC content, and enhanced in heterochromatic regions. Our results are consistent with a model where elevated risk at neighbouring bases is linked to lesion formation at the focal cytosine and subsequent long-patch repair. Our results provide evidence that cytosine methylation has a broader mutational footprints than commonly assumed. They also illustrate that methylation is not intrinsically associated with higher mutation risk for surrounding bases, but that mutagenic effects reflect evolved species-specific and lesion-specific predispositions to elicit error-prone long-patch DNA repair.

genomics↗

bioRxiv2019

Chromatinization of Escherichia coli with archaeal histones

Nucleosomes restrict DNA accessibility throughout eukaryotic genomes, with repercussions for replication, transcription, and other DNA-templated processes. How this globally restrictive organization emerged from a presumably more open ancestral state remains poorly understood. Here, to better understand the challenges associated with establishing globally restrictive chromatin, we express histones in a naive bacterial system that has not evolved to deal with nucleosomal structures: Escherichia coli. We find that histone proteins from the archaeon Methanothermus fervidus assemble on the E. coli chromosome in vivo and protect DNA from micrococcal nuclease digestion, allowing us to map binding footprints genome-wide. We provide evidence that nucleosome occupancy along the E. coli genome tracks intrinsic sequence preferences but is disturbed by ongoing transcription and replication. Notably, we show that higher nucleosome occupancy at promoters and across gene bodies is associated with lower transcript levels, consistent with local repressive effects. Surprisingly, however, this sudden enforced chromatinization has only mild repercussions for growth, suggesting that histones can become established as ubiquitous chromatin proteins without interfering critically with key DNA-templated processes. Our results have implications for the evolvability of transcriptional ground states and highlight chromatinization by archaeal histones as a potential avenue for controlling genome accessibility in synthetic prokaryotic systems.

systems biology↗

bioRxiv2019

The DNA-binding protein HTa from Thermoplasma acidophilum is an archaeal histone analog

Histones are a principal constituent of chromatin in eukaryotes and fundamental to our understanding of eukaryotic gene regulation. In archaea, histones are phylogenetically widespread, often highly abundant, but not universal: several archaeal lineages have lost histone genes from their coding repertoire. What prompted or facilitated these losses and how archaea without histones organize their chromatin remains largely unknown. Here, we use micrococcal nuclease digestion followed by high-throughput sequencing (MNase-Seq) to elucidate primary chromatin architecture in an archaeon without histones, the acido-thermophilic archaeon Thermoplasma acidophilum. We confirm and extend prior results showing that T. acidophilum harbours a HU family protein, HTa, that is highly expressed and protects a sizeable fraction of the genome from MNase digestion. Charting HTa-based chromatin architecture across the growth cycle and comparing it to that of three histone-encoding archaea (Methanothermus fervidus, Thermococcus kodakarensis and Haloferax volcanii), we then present evidence that HTa is an archaeal histone analog. HTa-protected fragments are GC-rich, display histone-like mono- and dinucleotide patterns around a conspicuous dyad, exhibit relatively invariant positioning throughout the growth cycle, and show archaeal histone-like oligomerization dynamics. Our results suggest that HTa, a DNA-binding protein of bacterial origin, has converged onto an architectural role filled by histones in other archaea.

microbiology↗

bioRxiv2018

Horizontal gene flow into Geobacillus is constrained by the chromosomal organization of growth and sporulation

Horizontal gene transfer (HGT) in bacteria occurs in the context of adaptive genome architecture. As a consequence, some chromosomal neighbourhoods are likely more permissive to HGT than others. Here, we investigate the chromosomal topology of horizontal gene flow into a clade of Bacillaceae that includes Geobacillus spp. Reconstructing HGT patterns using a phylogenetic approach coupled to model-based reconciliation, we discover three large contiguous chromosomal zones of HGT enrichment. These zones encompass and connect classically defined genomic islands. Analyzing topological and strand biases of recent and older transfer events, we show that restrictions on entry are rapidly enforced by selection and that restrictive and permissive zones have existed in their current locations for long periods of evolution. The largest zone, characterized by a high influx of metabolic genes, is centred on the terminus. The other two zones flank a narrow non-permissive zone around the origin of replication and extend to delimit the first third of the chromosome - the part of the chromosome that is confined to the forespore during early spore formation. Horizontal transfers into this area are biased towards functions classically controlled by the forespore-specific sigma factor {sigma}F: signal transduction, transcription, and particularly membrane biogenesis. Similar enrichment patterns are present in spore-forming but absent in non-spore-forming Bacilli. Our results suggest that the topology of HGT in Geobacillus, and Bacilli more generally, reflects constraints imposed by chromosomal organization for fast and sporulation, as asymmetric chromosomal entrapment in the forespore during early spore formation restricts where HGT-driven innovation in sporulation can occur.

evolutionary biology↗