Biology subjects

Doye, J. P. K.

Publications and source records attributed to Doye, J. P. K..

7 recordsLinked to original sources

bioRxiv2024

Controlling DNA-RNA strand displacement kinetics with base distribution

DNA-RNA hybrid strand displacement underpins the function of many natural and engineered systems. Understanding and controlling factors affecting DNA-RNA strand displacement reactions is necessary to enable control of processes such as CRISPR-Cas9 gene editing. By combining multi-scale modelling with strand displacement experiments we show that the distribution of bases along the displacement domain of an invading strand has a very strong effect on reaction kinetics. Merely by redistributing bases within a displacement domain of fixed base composition, we are able to design sequences whose reaction rates span more than two orders of magnitude. We characterize this effect in reactions involving the invasion of dsDNA by an RNA strand and invasion of a hybrid duplex by a DNA strand. We show that oxNA, a recently introduced coarse-grained model of DNA-RNA hybrids, can reproduce trends in experimentally observed reaction rates. We also develop a kinetic model for predicting strand displacement rates. On the basis of these results, we argue that base distribution effects are likely to play an important role in the function of the guide RNAs that direct CRISPR-Cas systems.

biophysics↗

bioRxiv2024

Punctuated and continuous structural diversity of S-layers across the prokaryotic tree of life

Surface layers (S-layers) are two-dimensional (2D) crystalline lattices that frequently coat prokaryotic cells, playing a crucial role in protection, maintaining cellular integrity, and mediating environmental interactions. However, the molecular landscape of these abundant proteins has remained underexplored due to a lack of structural data. By employing AlphaFold2multimer together with planar symmetry constraints in a workflow validated by electron cryomicroscopy structure determination, we have elucidated the lattice structures of over 150 S-layers from diverse archaea and bacteria. Our findings unveil a multifaceted evolutionary landscape for S-layer proteins, highlighting key differences in the evolution of bacterial and archaeal S-layers. Our study allows us to discover underlying patterns in S-layer structure, organisa-tion, and cell anchoring mechanisms across the prokaryotic tree of life, deepening our understanding of the intricately complex microbial cell surfaces, which appear to have evolved proteinaceous S-layers independently on multiple occasions. This work will open avenues for rational manipulation of prokaryotic cellular interactions in multicellular microbiomes, as well as for innovative 2D biomaterial design.

molecular biology↗

bioRxiv2024

Reconfigurable multi-component nanostructures built from DNA origami voxels

In cells, proteins rapidly self-assemble into sophisticated nanomachines. Bio-inspired self-assembly approaches, such as DNA origami, have achieved complex 3D nanostructures and devices. However, current synthetic systems are limited by lack of structural diversity, low yields in hierarchical assembly, and challenges in reconfiguration. Here, we develop a modular system of DNA origami voxels with programmable 3D connections. We demonstrate multifunctional pools of up to 12 unique voxels that can assemble into many shapes, prototyping 50 structures. Multi-step assembly pathways with sequential reduction in conformational freedom were then explored to increase yield. Voxels were first assembled into flexible chains and then folded into rigid structures, increasing yield 100-fold. Furthermore, programmable switching of local connections between flexible and rigid states achieved rapid and reversible reconfiguration of global structures. We envision that foldable chains of DNA origami voxels can be integrated with scalable assembly methods to achieve new levels of complexity in reconfigurable nanomaterials.

synthetic biology↗

bioRxiv2021

The interplay of supercoiling and thymine dimers inDNA

AO_SCPLOWBSTRACTC_SCPLOWThymine dimers are a major mutagenic photoproduct induced by UV radiation. While they have been the subject of extensive theoretical and experimental investigations, questions of how DNA supercoiling affects local defect properties, or, conversely, how the presence of such defects changes global supercoiled structure, are largely unexplored. Here we introduce a model of thymine dimers in the oxDNA forcefield, parametrised by comparison to melting experiments and structural measurements of the thymine dimer induced bend angle. We performed extensive molecular dynamics simulations of double-stranded DNA as a function of external twist and force. Compared to undamaged DNA, the presence of a thymine dimer lowers the supercoiling densities at which plectonemes and bubbles occur. For biologically relevant supercoiling densities and forces, thymine dimers can preferentially segregate to the tips of the plectonemes, where they enhance the probability of a localized tip-bubble. This mechanism increases the probability of highly bent and denatured states at the thymine dimer site, which may facilitate repair enzyme binding. Thymine dimer-induced tip-bubbles also pin plectonemes, which may help repair enzymes to locate damage. We hypothesize that the interplay of supercoiling and local defects plays an important role for a wider set of DNA damage repair systems.

biophysics↗

bioRxiv2021

Symmetry and simplicity spontaneously emerge from the algorithmic nature of evolution

Engineers routinely design systems to be modular and symmetric in order to increase robustness to perturbations and to facilitate alterations at a later date. Biological structures also frequently exhibit modularity and symmetry, but the origin of such trends is much less well understood. It can be tempting to assume - by analogy to engineering design - that symmetry and modularity arise from natural selection. But evolution, unlike engineers, cannot plan ahead, and so these traits must also afford some immediate selective advantage which is hard to reconcile with the breadth of systems where symmetry is observed. Here we introduce an alternative non-adaptive hypothesis based on an algorithmic picture of evolution. It suggests that symmetric structures preferentially arise not just due to natural selection, but also because they require less specific information to encode, and are therefore much more likely to appear as phenotypic variation through random mutations. Arguments from algorithmic information theory can formalise this intuition, leading to the prediction that many genotype-phenotype maps are exponentially biased towards phenotypes with low descriptional complexity. A preference for symmetry is a special case of this bias towards compressible descriptions. We test these predictions with extensive biological data, showing that that protein complexes, RNA secondary structures, and a model gene-regulatory network all exhibit the expected exponential bias towards simpler (and more symmetric) phenotypes. Lower descriptional complexity also correlates with higher mutational robustness, which may aid the evolution of complex modular assemblies of multiple components.

evolutionary biology↗

bioRxiv2020

Designer protein assemblies with tunable phase diagrams in living cells

The self-organization of proteins into specific assemblies is a hallmark of biological systems. Principles governing protein-protein interactions have long been known. However, principles by which such nanoscale interactions generate diverse phenotypes of mesoscale assemblies, including phase-separated compartments, remains challenging to characterize and understand. To illuminate such principles, we create a system of two proteins designed to interact and form mesh-like assemblies in living cells. We devise a novel strategy to map high-resolution phase diagrams in vivo, which provide mesoscale self-assembly signatures of our system. The structural modularity of the two protein components allows straightforward modification of their molecular properties, enabling us to characterize how point mutations that change their interaction affinity impact the phase diagram and material state of the assemblies in vivo. Both, the phase diagrams and their dependence on interaction affinity were captured by theory and simulations, including out-of-equilibrium effects seen in growing cells. Applying our system to interrogate biological mechanisms of self-assembly, we find that co-translational protein binding suffices to recruit an mRNA to the designed micron-scale structures.Competing Interest StatementThe authors have declared no competing interest.View Full Text

synthetic biology↗

bioRxiv2018

Substrate conformational dynamics drive structure-specific recognition of gapped DNA by DNA polymerase

DNA-binding proteins utilise different recognition mechanisms to locate their DNA targets. Some proteins recognise specific nucleotide sequences, while many DNA repair proteins interact with specific (often bent) DNA structures. While sequence-specific DNA binding mechanisms have been studied extensively, structure-specific mechanisms remain unclear. Here, we study structure-specific DNA recognition by examining the structure and dynamics of DNA polymerase I (Pol) substrates both alone and in Pol-DNA complexes. Using a rigid-body docking approach based on a network of 73 distance restraints collected using single-molecule FRET, we determined a novel solution structure of the singlenucleotide-gapped DNA-Pol binary complex. The structure was highly consistent with previous crystal structures with regards to the downstream primer-template DNA substrate; further, our structure showed a previously unobserved sharp bend (~120{degrees}) in the DNA substrate; we also showed that this pronounced bending of the substrate is present in living bacteria. All-atom molecular dynamics simulations and single-molecule quenching assays revealed that 4-5 nt of downstream gap-proximal DNA are unwound in the binary complex. Coarsegrained simulations on free gapped substrates reproduced our experimental FRET values with remarkable accuracy (<{Delta}FRET> = -0.0025 across 34 independent distances) and revealed that the one-nucleotide-gapped DNA frequently adopted highly bent conformations similar to those in the Pol-bound state ({Delta}G < 4 kT); such conformations were much less accessible to nicked (> 7 kT) or duplex (>> 10 kT) DNA. Our results suggest a mechanism by which Pol and other structure-specific DNA-binding proteins locate their DNA targets through sensing of the conformational dynamics of DNA substrates.\n\nSignificance StatementMost genetic processes, including DNA replication, repair and transcription, rely on DNA-binding proteins locating specific sites on DNA; some sites contain a specific sequence, whereas others present a specific structure. While sequence-specific recognition has a clear physical basis, structure-specific recognition mechanisms remain obscure. Here, we use single-molecule FRET and computer simulations to show that the conformational dynamics of an important repair intermediate (1nt-gapped DNA) act as central recognition signals for structure-specific binding by DNA polymerase I (Pol). Our conclusion is strongly supported by a novel solution structure of the Pol-DNA complex wherein the gapped-DNA is significantly bent. Our iterative approach combining precise single-molecule measurements with molecular modelling is general and can elucidate the structure and dynamics for many large biomachines.

biophysics↗