Biology subjects

Beltran, T.

Publications and source records attributed to Beltran, T..

9 recordsLinked to original sources

bioRxiv2024

The allosteric landscape of the Src kinase

Enzymes catalyze the reactions of life and are the targets of most small molecule drugs. Most drugs target conserved enzyme active sites, often causing problems of specificity and toxicity. Targeting allosteric sites can increase specificity, overcome resistance mutations, and allow fine-tuning of activity. However, most enzymes have no known allosteric sites and methods do not exist to comprehensively identify them. Here we present a general and fast approach to chart allosteric communication in enzymes and apply it to the Src kinase to produce the first comprehensive map of negative and positive allosteric control of an enzymatic activity. Allostery in the Src kinase domain is pervasive, anisotropic, partially predictable, and modulated by regulatory domains. Multiple surface pockets of Src are allosterically active and so genetically-prioritized for the development of inhibitory and activating drugs. Using this approach it should be possible to chart global allosteric maps of many kinases and other enzymes important for medicine and biotechnology. HighlightsO_LIFirst comprehensive map of negative and positive allosteric control of an enzymatic activity, the Src kinase. C_LIO_LIAllosteric communication is pervasive, distance dependent, and anisotropic. C_LIO_LIAllostery is conserved and modulated in the presence of the Src regulatory domains. C_LIO_LIGenetic prioritization of druggable surface pockets for Src inhibition and activation. C_LIO_LIAllosteric maps can now be constructed for many medically and industrially important kinases and enzymes. C_LI

biophysics↗

bioRxiv2024

Site saturation mutagenesis of 500 human protein domains reveals the contribution of protein destabilization to genetic disease

Missense variants that change the amino acid sequences of proteins cause one third of human genetic diseases1. Tens of millions of missense variants exist in the current human population, with the vast majority having unknown functional consequences. Here we present the first large-scale experimental analysis of human missense variants across many different proteins. Using DNA synthesis and cellular selection experiments we quantify the impact of >500,000 variants on the abundance of >500 human protein domains. This dataset, Human Domainome 1, reveals that >60% of pathogenic missense variants reduce protein stability. The contribution of stability to protein fitness varies across proteins and diseases, and is particularly important in recessive disorders. Combining stability measurements with protein language models annotates functional sites across proteins. Mutational effects on stability are largely conserved in homologous domains, allowing accurate stability prediction across entire protein families using energy models. Domainome 1 demonstrates the feasibility of assaying human protein variants at scale and provides a large consistent reference dataset for clinical variant interpretation and the training and benchmarking of computational methods.

genomics↗

bioRxiv2023

Deep indel mutagenesis reveals the impact of insertions and deletions on protein stability and function

Amino acid insertions and deletions (indels) are an abundant class of genetic variants. However, compared to substitutions, the effects of indels on protein stability are not well understood and are poorly predicted. To better understand indels here we analyze new and existing large-scale deep indel mutagenesis (DIM) of structurally diverse proteins. The effects of indels on protein stability vary extensively among and within proteins and are not well predicted by existing computational methods. To address this shortcoming we present INDELi, a series of models that combine experimental or predicted substitution effects and secondary structure information to provide good prediction of the effects of indels on both protein stability and pathogenicity. Moreover, quantifying the effects of indels on protein-protein interactions suggests that insertions can be an important class of gain-of-function variants. Our results provide an overview of the impact of indels on proteins and a method to predict their effects genome-wide.

genomics↗

bioRxiv2020

Integrator terminates promoter-proximal Pol II to generate C. elegans piRNA precursors

Piwi-interacting RNAs (piRNAs) play key roles in germline development and genome defence in metazoans. In C. elegans, piRNAs are transcribed from >15000 discrete genomic loci by RNA polymerase II, resulting in 28 nt short-capped piRNA precursors. Here we investigate transcription termination at piRNA loci. We show that the Integrator complex, which terminates snRNA transcription, is recruited to piRNA loci. We show that the catalytic activity of Integrator cleaves nascent capped piRNA precursors associated with promoter-proximal Pol II, resulting in termination of transcription. Loss of Integrator activity, however, does not result in transcriptional readthrough at the majority of piRNA loci. Our results draw new parallels between snRNA and piRNA biogenesis in nematodes, and provide evidence of a role for the Integrator complex as a terminator of promoter-proximal RNA polymerase II. Highlights- Integrator localises to sites of piRNA biogenesis in nematodes - Integrator cleaves nascent RNAs associated with promoter-proximal Pol II at piRNA loci to release short capped piRNA precursors from chromatin - Repression of Pol II elongation at the majority of piRNA loci is independent of Integrator

molecular biology↗

bioRxiv2020

The RNA Polymerase II core subunit RPB-9 directs transcriptional elongation at piRNA loci in Caenorhabditis elegans

PIWI-interacting RNAs (piRNAs) are genome-encoded small RNAs that regulate germ cell development and maintain germline integrity in many animals. Mature piRNAs engage Piwi Argonaute proteins to silence complementary transcripts, including transposable elements and endogenous genes. piRNA biogenesis mechanisms are diverse and remain poorly understood. Here, we identify the RNA Polymerase II (RNA Pol II) core subunit RPB-9 as required for piRNA-mediated silencing in the nematode Caenorhabditis elegans. rpb-9 mutants fail to initiate heritable piRNA-mediated gene silencing. Furthermore, we show that RPB-9 is required to repress two DNA transposon families and a subset of somatic genes in the C. elegans germline. We provide genetic and biochemical evidence that RPB-9 is required for piRNA biogenesis. We demonstrate that RPB-9 acts to promote transcriptional elongation/termination at endogenous piRNA loci. We conclude that as a part of its rapid evolution the piRNA pathway has co-opted another ancient machinery, this time for high-fidelity transcription.

genetics↗

bioRxiv2019

Epimutations driven by small RNAs arise frequently but have limited duration in a metazoan organism

Epigenetic regulation involves changes in gene expression independent of DNA sequence variation that are inherited through cell division (Holliday, 2006). In addition to a fundamental role in cell differentiation, some epigenetic changes can also be transmitted transgenerationally through meiosis (Heard and Martienssen, 2014). Epigenetic alterations ("epimutations") could thus contribute to heritable variation within populations and be subject to evolutionary processes such as natural selection and drift (Burggren, 2016). However, this suggestion is controversial, partly because unlike classical mutations involving DNA sequence changes, key parameters such as the rate at which epimutations arise and their persistence are unknown. Here, we perform the first genome-wide study of epimutations in a metazoan organism. We use experimental evolution to characterise the rate, spectrum and stability of epimutations driven by small silencing RNAs in the model nematode C. elegans. We show that epimutations arise spontaneously at a rate [~]25 times greater than DNA sequence changes and typically have short half-lives of 2-3 generations. Nevertheless, some epimutations last at least 10 generations. Epimutations thus may contribute to evolutionary processes over a short timescale but are unlikely to bring about long-term divergence without further DNA sequence changes.

genetics↗

bioRxiv2019

Long-term experimental evolution reveals purifying selection on piRNA-mediated control of transposable element expression

Transposable elements (TEs) are an almost universal constituent of eukaryotic genomes. In animals, Piwi-interacting small RNAs (piRNAs) and repressive chromatin often play crucial roles in preventing TE transcription and thus restricting TE activity. Nevertheless, TE content varies widely across eukaryotes and the dynamics of TE activity and TE silencing across evolutionary time is poorly understood. Here we used experimentally evolved populations of C. elegans to study the dynamics of TE expression over 400 generations. The experimental populations were evolved at three different population sizes to manipulate the efficiency of natural selection versus genetic drift. We demonstrate increased TE expression relative to the ancestral population, with the largest increases occurring in the smallest populations. We show that the transcriptional activation of TEs within active regions of the genome is associated with failure of piRNA-mediated silencing, whilst desilenced TEs in repressed chromatin domains retain small RNAs. Additionally, we find that the sequence context of the surrounding region influences the propensity of TEs to lose silencing through failure of small RNA-mediated silencing. Together, our results show that natural selection in C. elegans is responsible for maintaining low levels of TE expression, and provide new insights into the epigenomic features responsible.

molecular biology↗

bioRxiv2018

Comparative genomics of ten new Caenorhabditis species

The nematode Caenorhabditis elegans has been central to the understanding of metazoan biology. However, C. elegans is but one species among millions and the significance of this important model organism will only be fully revealed if it is placed in a rich evolutionary context. Global sampling efforts have led to the discovery of over 50 putative species from the genus Caenorhabditis, many of which await formal species description. Here, we present species descriptions for ten new Caenorhabditis species. We also present draft genome sequences for nine of these new species, along with a transcriptome assembly for one. We exploit these whole-genome data to reconstruct the Caenorhabditis phylogeny and use this phylogenetic tree to dissect the evolution of morphology in the genus. We show unexpected complexity in the evolutionary history of key developmental pathway genes. The genomic data also permit large scale analysis of gene structure, which we find to be highly variable within the genus. These new species and the associated genomic resources will be essential in our attempts to understand the evolutionary origins of the C. elegans model.

evolutionary biology↗

bioRxiv2018

Evolutionary analysis implicates RNA polymerase II pausing and chromatin structure in nematode piRNA biogenesis

Piwi-interacting RNAs (piRNAs) control transposable elements widely across metazoans but have rapidly evolving biogenesis pathways. In Caenorhabditis elegans, almost all piRNA loci are found within two 3Mb clusters on Chromosome IV. Each piRNA locus possesses an upstream motif that recruits RNA polymerase II to produce a [~]28 nt precursor transcript. Here, we use comparative epigenomics across nematodes to gain insight into piRNA biogenesis. We show that the piRNA upstream motif is derived from core promoter elements controlling snRNA biogenesis. We describe two alternative modes of piRNA organisation in nematodes: in C. elegans and closely related nematodes, piRNAs are clustered within repressive H3K27me3 chromatin, whilst in other species, typified by Pristionchus pacificus, piRNAs are distributed genome-wide within introns of actively transcribed genes. In both groups, piRNA production depends on downstream sequence signals associated with RNA polymerase II pausing, which synergise with the chromatin environment to control piRNA precursor transcription.

genomics↗