Biology subjects

Yesselman, J. D.

Publications and source records attributed to Yesselman, J. D..

11 recordsLinked to original sources

bioRxiv2026

Single-base substitutions switch RNA tertiary allostery between positive and negative coupling.

Riboswitches regulate gene expression in response to ligand binding, remodeling their secondary structure to terminate transcription or block translation. This innate switching has driven efforts to repurpose riboswitches as synthetic control elements. Although promising, tuning riboswitch responses to new ligands and functions has proven difficult. Large RNAs such as the ribosome and RNase P exhibit an alternative switching mode via the docking and undocking of tertiary contacts. These transitions are buried deep within the machines, and there is no minimal system to study them in isolation. To overcome this limitation, we built a minimal 3D-structure ligand-inducible switch. We started with a previously designed nanostructure containing an ATP-aptamer and a tetraloop/tetraloop receptor (TL/TLR) tertiary contact. DMS-MaPseq screening of 3,375 mutants of the two linking motifs, a kink-turn and a 4-1 junction, identified 237 variants in which AMP binding undocked the TL/TLR and 120 in which it drove docking. Switching arose almost entirely from mutations in the conserved sheared G{middle dot}A base pairs of the kink-turn. Fitting four representative constructs AMP titrations to a linked-equilibrium model yielded coupling free energies spanning 3.7 kcal/mol, and magnesium titrations with and without AMP independently confirmed these couplings while revealing a three-state docking pathway in mutants lacking wild-type coupling. Single nucleotides inserted into the kink-turn motif adjust the sign and strength of coupling without redesigning the secondary structure. This simple system thus provides a platform both as a model for tertiary switching in other large RNA machines and as a foundation for designing synthetic control elements based on tertiary interactions.

biochemistry↗

bioRxiv2025

Quantitative Thermodynamic Characterization of Self-Assembling RNA Nanostructures

Recent developments in RNA nanotechnology have led to the rise in designing specific higher order RNA structures with functional goals in mind, such as drug delivery and immunomodulation. As researchers create RNA nanostructures with the goal of becoming common in the molecular biologists toolkit, more investigation is required on the robustness of RNA designs. Primarily, what different molecular contexts are the designed and intended nanostructures stable in? In this work we show that by using second-order right-angle light scattering, that RNA nanostructure self-assembly is highly sensitive to environmental conditions. While a test RNA hexagonal grid nanostructure that forms correctly though 120{degrees} kissing loops under ideal conditions, small variations in salt conditions and annealing times cause the nanostructure to form less structured variants. Tertiary contacts for self-assembly require magnesium and break over a broad range of low temperatures, melting at 42 {degrees}C. In contrast this was found to be considerably lower than the secondary structure melting which occurred at 75 {degrees}C. This work underscores the importance of quantitative and thermodynamic characterization of self-assembling nanostructures as they begin to be deployed for engineering and therapeutic applications.x1

biochemistry↗

bioRxiv2024

Analysis of natural structures and chemical mapping data reveals local stability compensation in RNA

RNA molecules adopt complex structures that perform essential biological functions across all forms of life, making them promising candidates for therapeutic applications. However, our ability to design new RNA structures remains limited by an incomplete understanding of their folding principles. While global metrics such as the minimum free energy are widely used, they are at odds with naturally occurring structures and incompatible with established design rules. Here, we introduce local stability compensation (LSC), a principle that RNA folding is governed by the local balance between destabilizing loops and their stabilizing adjacent stems, challenging the focus on global energetic optimization. Analysis of over 100,000 RNA structures revealed that LSC signatures are particularly pronounced in bulges and their adjacent stems, with distinct patterns across different RNA families that align with their biological functions. To validate LSC experimentally, we systematically analyzed thousands of RNA variants using DMS chemical mapping. Our results demonstrate that stem folding, as measured by reactivity, correlates with LSC (R2 = 0.458 for hairpin loops) and that instabilities show no significant effect on folding for distal stems. These findings demonstrate that LSC can be a guiding principle for understanding RNA function and for the rational design of custom RNAs. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=74 SRC="FIGDIR/small/627843v2_ufig1.gif" ALT="Figure 1"> View larger version (21K): org.highwire.dtl.DTLVardef@a493bdorg.highwire.dtl.DTLVardef@df7a58org.highwire.dtl.DTLVardef@1d946a0org.highwire.dtl.DTLVardef@1abedcb_HPS_FORMAT_FIGEXP M_FIG C_FIG

biophysics↗

bioRxiv2024

A quantitative framework for structural interpretation of DMS reactivity

Dimethyl sulfate (DMS) chemical mapping probes RNA structure, where low reactivity is generally interpreted as Watson-Crick (WC) base pairs and high reactivity as unpaired nucleotides. Studies examining DMS reactivity of RNAs with known 3D structures have identified nucleotides that deviate from this interpretation with distinct solvent accessibility and hydrogen bonding patterns. Understanding the frequency of these outliers and their recurring structural 3D features remains incomplete. To address this knowledge gap, we systematically analyzed DMS reactivity patterns across a library of 7,500 RNA constructs containing two-way junctions with known 3D structures. We observe DMS reactivity exists on a continuum over four orders of magnitude with approximately 10% overlap in reactivity between WC and non-WC nucleotides. We find that non-WC bases with WC-like DMS protection exhibit increased hydrogen bonding and decreased solvent accessibility, whereas WC pairs exhibiting greater DMS reactivity tend to flank junctions, correlating with weaker base stacking and greater junction dynamics. Furthermore, we discover that DMS reactivity values in non-canonical pairs correlate with atomic distances and base pair geometry, enabling discrimination between different 3D conformations. These DMS reactivity patterns indicate that DMS reactivity provides atomic-scale information about RNA 3D conformations, which can be used to model RNA structures and dynamics.

biochemistry↗

bioRxiv2024

High-throughput determination of RNA tertiary contact thermodynamics by quantitative DMS chemical mapping

Structured RNAs often contain long-range tertiary contacts that are critical to their function. Despite the importance of tertiary contacts, methods to measure their thermodynamics are low throughput or require specialized instruments. Here, we introduce a new quantitative chemical mapping method (qDMS-MaPseq) to measure Mg2+-induced formation of tertiary contact thermodynamics in a high-throughput manner using standard biochemistry equipment. With qDMS-MaPseq, we measured the {Delta}G of 98 unique tetraloop/tetraloop receptor (TL/TLR) variants in a one-pot reaction. These results agree well with measurements from specialized instruments (R2=0.64). Furthermore, the DMS reactivity of the TL directly correlates to the stability of the contact (R2=0.68), the first direct evidence that DMS reactivity reports on thermodynamics. Combined with structure prediction, DMS reactivity allowed the development of experimentally accurate 3D models of TLR mutants. These results demonstrate that qDMS-MaPseq is broadly accessible, high-throughput, and directly links DMS reactivity to thermodynamics.

biochemistry↗

bioRxiv2023

Visualizing a two-state conformational ensemble in stem-loop 3 of the transcriptional regulator 7SK RNA

Structural plasticity is integral to RNA function; however, there are currently few methods to quantitatively resolve RNAs that have multiple structural states. NMR spectroscopy is a powerful approach for resolving conformational ensembles but is size-limited. Chemical probing is well-suited for large RNAs but provides limited structural and no kinetics information. Here, we integrate the two approaches to visualize a two-state conformational ensemble for the central stem-loop 3 (SL3) of 7SK RNA, a critical element for 7SK RNA function in transcription regulation. We find that the SL3 distal end exchanges between two equally populated yet structurally distinct states in both isolated SL3 constructs and full-length 7SK RNA. We rationally designed constructs that lock SL3 into a single state and demonstrate that both chemical probing and NMR data fit to a linear combination of the two states. Comparison of vertebrate 7SK RNA sequences shows conservation of both states, suggesting functional importance. These results provide new insights into 7SK RNA structural dynamics and demonstrate the utility of integrating chemical probing with NMR spectroscopy to gain quantitative insights into RNA conformational ensembles.

biophysics↗

bioRxiv2020

Amilorides inhibit SARS-CoV-2 replication in vitro by targeting RNA structures

The SARS-CoV-2 pandemic, and the likelihood of future coronavirus pandemics, has rendered our understanding of coronavirus biology more essential than ever. Small molecule chemical probes offer to both reveal novel aspects of virus replication and to serve as leads for antiviral therapeutic development. The RNA-biased amiloride scaffold was recently tuned to target a viral RNA structure critical for translation in enterovirus 71, ultimately uncovering a novel mechanism to modulate positive-sense RNA viral translation and replication. Analysis of CoV RNA genomes reveal many conserved RNA structures in the 5-UTR and proximal region critical for viral translation and replication, including several containing bulge-like secondary structures suitable for small molecule targeting. Following phylogenetic conservation analysis of this region, we screened an amiloride-based small molecule library against a less virulent human coronavirus, OC43, to identify lead ligands. Amilorides inhibited OC43 replication as seen in viral plaque assays. Select amilorides also potently inhibited replication competent SARS-CoV-2 as evident in the decreased levels of cell free virions in cell culture supernatants of treated cells. Reporter screens confirmed the importance of RNA structures in the 5-end of the viral genome for small molecule activity. Finally, NMR chemical shift perturbation studies of the first six stem loops of the 5-end revealed specific amiloride interactions with stem loops 4, 5a, and 6, all of which contain bulge like structures and were predicted to be strongly bound by the lead amilorides in retrospective docking studies. Taken together, the use of multiple orthogonal approaches allowed us to identify the first small molecules aimed at targeting RNA structures within the 5-UTR and proximal region of the CoV genome. These molecules will serve as chemical probes to further understand CoV RNA biology and can pave the way for the development of specific CoV RNA-targeted antivirals.

microbiology↗

bioRxiv2020

An RNA dynamic ensemble at atomic resolution

Biomolecules do not fold into a single 3D structure but rather form dynamic ensembles of many inter-converting conformations1. Knowledge of dynamic ensembles is key for understanding how biomolecules fold and function, and for rationally manipulating their activities in drug discovery and synthetic biology2-4. However, solving dynamic ensembles of biomolecules at atomic resolution is a major challenge in structural biology because the information required to specify the position of all atoms in thousands of conformations in an ensemble far exceeds the information content of experimental measurements. Here we addressed the data gap and dramatically simplified and accelerated RNA ensemble determination by using structure prediction tools that leverage the growing database of RNA structures to generate a conformational library. Library refinement with NMR residual dipolar couplings enabled determination of an atomic-resolution ensemble for HIV-1 TAR as confirmed by quantum-mechanical calculations of NMR chemical shifts, comparison to a crystal structure of a substate, and through the successful redistribution of the ensemble by design using atomic mutagenesis. The ensemble provides an unprecedented view of how bulge residues cooperatively flip out and undergo sugar repuckering to allow the adjoining helices to stack. The generality of this approach will make determination of atomic-resolution RNA ensembles routine.

biophysics↗

bioRxiv2019

Ribosolve: Rapid determination of three-dimensional RNA-only structures

The discovery and design of biologically important RNA molecules is dramatically outpacing three-dimensional structural characterization. To address this challenge, we present Ribosolve, a hybrid method integrating moderate-resolution cryo-EM maps, chemical mapping, and Rosetta computational modeling, and demonstrate its application to thirteen previously unknown 119-to 338-nucleotide protein-free RNA-only structures: full-length Tetrahymena ribozyme, hc16 ligase with and without substrate, full-length V. cholerae and F. nucleatum glycine riboswitch aptamers with and without glycine, Mycobacterium SAM-IV riboswitch with and without S-adenosylmethionine, and computer-designed spinach-TTR-3, eterna3D-JR_1, and ATP-TTR-3 with and without AMP. Blind challenges, prospective compensatory mutagenesis, internal controls, and simulation benchmarks validate the Ribosolve models and establish that modeling convergence is quantitatively predictive of model accuracy. These results demonstrate that RNA-only 3D structure determination can be rapid and routine.

biophysics↗

bioRxiv2018

RNA tertiary structure energetics predicted by an ensemble model of the RNA double helix

Over 50% of residues within functional structured RNAs are base-paired in Watson-Crick helices, but it is not fully understood how these helices geometric preferences and flexibility might influence RNA tertiary structure. Here, we show experimentally and computationally that the ensemble fluctuations of RNA helices substantially impact RNA tertiary structure stability. We updated a model for the conformational ensemble of the RNA helix using crystallographic structures of Watson-Crick base pair steps. To test this model, we made blind predictions of the thermodynamic stability of >1500 tertiary assemblies with differing helical sequences and compared calculations to independent measurements from a high-throughput experimental platform. The blind predictions accounted for thermodynamic effects from changing helix sequence and length with unexpectedly tight accuracies (RMSD of 0.34 and 0.77 kcal/mol, respectively). These comparisons lead to a detailed picture of how RNA base pair steps fluctuate within complex assemblies and suggest a new route toward predicting RNA tertiary structure formation and energetics.

biophysics↗

bioRxiv2017

Computational Design of Asymmetric Three-dimensional RNA Structures and Machines.

The emerging field of RNA nanotechnology seeks to create nanoscale 3D machines by repurposing natural RNA modules, but successes have been limited to symmetric assemblies of single repeating motifs. We present RNAMake, a suite that automates design of RNA molecules with complex 3D folds. We first challenged RNAMake with the paradigmatic problem of aligning a tetraloop and sequence-distal receptor, previously only solved via symmetry. Single-nucleotide-resolution chemical mapping, native gel electrophoresis, and solution x-ray scattering confirmed that 11 of the 16 miniTTR designs successfully achieved clothespin-like folds. A 2.55 [A] diffraction-resolution crystal structure of one design verified formation of the target asymmetric nanostructure, with large sections achieving near-atomic accuracy (< 2.0 [A]). Finally, RNAMake designed asymmetric segments to tether the 16S and 23S rRNAs together into a synthetic singlestranded ribosome that remains uncleaved by ribonucleases and supports life in Escherichia coli, a challenge previously requiring several rounds of trial-and-error.

bioengineering↗