Using In Vitro and In-cell SHAPE to Investigate Small Molecule Induced Pre-mRNA Structural Changes
January 30th, 2019
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Detailed protocols for both in vitro and in-cell selective 2'-hydroxyl acylation analyzed by primer extension (SHAPE) experiments to determine the secondary structure of pre-mRNA sequences of interest in the presence of an RNA-targeting small molecule are presented in this article.
Overview
This article presents detailed protocols for in vitro selective 2'-hydroxyl acylation analyzed by primer extension (SHAPE) experiments. These methods are designed to determine the secondary structure of pre-mRNA sequences in the presence of RNA-targeting small molecules.
Key Study Components
Area of Science
- Neuroscience
- Biochemistry
- Molecular Biology
Background
- Understanding RNA secondary structures is crucial for elucidating their functions.
- SHAPE is a powerful technique for probing RNA structure in a cellular context.
- Small molecules can influence RNA structure and function.
- In vitro methods provide a controlled environment for these studies.
Purpose of Study
- To develop protocols for SHAPE experiments.
- To analyze RNA secondary structures in the presence of small molecules.
- To enhance the understanding of RNA dynamics and interactions.
Methods Used
- Preparation of RNA templates for SHAPE analysis.
- Radio labeling of reverse transcription primers.
- Incubation and activation of samples under specific conditions.
- Use of desalting columns for sample purification.
Main Results
- Protocols were successfully developed for in vitro SHAPE experiments.
- Secondary structures of RNA sequences were determined.
- Effects of RNA-targeting small molecules on RNA structure were analyzed.
- The methods demonstrated cost-effectiveness and efficiency.
Conclusions
- The developed protocols provide a reliable approach for studying RNA structures.
- SHAPE experiments can reveal important insights into RNA dynamics.
- Future studies can build on these methods to explore RNA-small molecule interactions.
Frequently Asked Questions
What is SHAPE?
SHAPE stands for selective 2'-hydroxyl acylation analyzed by primer extension, a technique used to study RNA secondary structures.
Why is RNA secondary structure important?
RNA secondary structure is crucial for understanding RNA function and interactions with proteins and small molecules.
How does the presence of small molecules affect RNA?
Small molecules can bind to RNA and alter its structure, potentially influencing its function and stability.
What are the advantages of in vitro methods?
In vitro methods allow for controlled experimental conditions, making it easier to study specific interactions and dynamics.
Can these protocols be applied to other RNA sequences?
Yes, the protocols can be adapted for various RNA sequences of interest.
Executive Industry Relevance
RNA-targeting small molecules require precise structural validation to confirm mechanism of action and de-risk therapeutic hypotheses. In vitro and in-cell SHAPE provide orthogonal, nucleotide-resolution insights into RNA structural changes induced by ligand binding, enabling early-stage target validation and predictive confidence in lead optimization. These methods support go/no-go decisions by distinguishing direct RNA effects from cellular context artifacts, reducing late-stage failure risk in nucleic acid drug discovery.
Strategic Applications in Biopharma R&D
Early Discovery & Target Validation
- Scientific Value: Quantifies ligand-induced RNA structural changes at single-nucleotide resolution to validate target engagement and mechanism of action.
- Operational Value: Enables rapid, cost-effective screening of small molecule effects on RNA folding without requiring cellular systems.
- Scientific Value: In-cell SHAPE captures RNA structure in native cellular context, preserving RNA-binding protein interactions lost in vitro.
- Operational Value: Supports lead identification by correlating structural perturbations with functional outcomes in disease-relevant pre-mRNA targets like SMN2 exon 7.
Screening & Assay Development
- Scientific Value: Provides quantitative, nucleotide-resolved reactivity profiles that serve as direct readouts for RNA structural dynamics.
- Operational Value: In vitro SHAPE uses PAGE-based detection for short RNAs (<200 nt), enabling low-cost, high-throughput screening campaigns.
- Operational Value: In-cell SHAPE leverages next-generation sequencing to analyze longer RNA targets (~1,000 nt), increasing assay scalability and target coverage.
- Scientific Value: Enables assay standardization through normalized SHAPE reactivity metrics, supporting cross-lab reproducibility and data integration.
Translational & Preclinical Research
- Scientific Value: Confirms structural conservation between in vitro models and cellular RNA, strengthening translational relevance of lead compounds.
- Operational Value: Facilitates mechanistic de-risking by distinguishing direct RNA binding from indirect cellular effects.
- Scientific Value: Supports biomarker development by linking RNA structural changes to splicing outcomes or target modulation in preclinical models.
- Operational Value: Informs preclinical advancement decisions by providing structural evidence of target engagement in disease-relevant tissues.
Pipeline & Workflow Integration
SHAPE methods integrate into the discovery continuum from early target validation through lead optimization to preclinical mechanistic studies, particularly for RNA-targeted therapeutics where structural validation is critical for progression.
- Discovery Biology: Enables hypothesis testing of RNA structural mechanisms and pathway clarification through direct observation of ligand-induced folding changes.
- Screening: Delivers assay-ready, quantitative structural readouts that support reproducible compound evaluation and structure-activity relationship (SAR) mapping.
- Analytics: Generates nucleotide-resolution reactivity data and differential SHAPE profiles that allow teams to quantify structural perturbations and compare compound efficacy.
- Translational Research: Bridges discovery and preclinical work by validating RNA structural effects in cellular contexts, ensuring target relevance beyond reductionist models.
- Enterprise Reuse: Establishes a reusable platform for RNA structural interrogation across multiple targets, modalities, and therapeutic areas.
Operational & Enterprise Impact
- Scientific Value: Increases predictive confidence in target validation by reducing mechanistic ambiguity in RNA-small molecule interactions.
- Operational Value: Enhances reproducibility and standardization through well-defined chemical modification and detection workflows.
- Strategic Value: Improves capital efficiency by enabling early de-risking of RNA targets, reducing investment in false positives.
- Portfolio Impact: Supports risk-adjusted prioritization by providing structural evidence to guide lead selection and advancement decisions.
Implementation Considerations
- Requires expertise in RNA biochemistry, radiolabeling safety protocols, and nucleic acid handling for in vitro SHAPE.
- Dependent on access to phosphorimaging equipment, polyacrylamide gel electrophoresis systems, and scintillation counters for radiolabeled detection.
- Necessitates cross-team standardization of RNA folding conditions, SHAPE reagent handling, and data analysis pipelines for reproducible results.
- In-cell SHAPE requires adaptation to cellular permeability, toxicity, and fixation protocols when extending to primary or disease-relevant cell lines.
- Practical limitations include RNA length constraints (~200 nt for in vitro PAGE, ~1,000 nt for in-cell NGS) and potential artifacts from overexpression systems or incomplete ligand equilibration.
Biopharma FAQs
Why does SHAPE reactivity change indicate RNA structural modulation?
Altered 2'-OH acylation rates reflect changes in nucleotide flexibility or base pairing, directly reporting on ligand-induced structural rearrangements in RNA. This enables quantification of structural perturbations at single-nucleotide resolution, supporting target validation in RNA-targeting small molecule programs.
How does isolating the small molecule as the independent variable improve target validation?
By keeping RNA sequence, folding conditions, and SHAPE reagent constant while varying only the small molecule concentration or structure, researchers can attribute observed SHAPE changes directly to ligand binding. This isolation strengthens causal inference between compound exposure and RNA structural effects, reducing confounding variables in early discovery.
What quantitative SHAPE measurements enable lead optimization decisions?
Differential SHAPE reactivity scores at specific nucleotides provide a quantitative readout of structural change magnitude and location, allowing correlation with functional assays like splicing modulation or binding affinity. These metrics support SAR modeling and help prioritize compounds with desired structural and functional profiles.
Why are replication requirements critical for cross-functional collaboration in SHAPE-based projects?
Biological and technical replicates ensure that observed SHAPE changes are reproducible and not due to experimental noise or batch effects, which is essential for data sharing between chemistry, biology, and computational teams. Consistent replication builds confidence in structural findings and supports unified go/no-go decisions across disciplines.
What statistical analysis is required before implementing SHAPE in a lead identification workflow?
Implementation requires normalization of SHAPE reactivity, calculation of significance thresholds (e.g., Z-scores or p-values) for differential reactivity, and correction for multiple testing across nucleotides. These analyses ensure that detected structural changes are statistically robust and not false positives, enabling reliable integration into compound screening and decision-making pipelines.
Chapters in this video
0:04
Title
0:31
32P-labeled Primer Labeling for In Vitro Selective 2‘-hydroxyl Acylation Analyzed by Primer Extension (SHAPE)
3:44
Small Molecule Binding and RNA 2‘-OH Modification
6:29
Marker Preparation and Primer Extension
8:59
PAGE Analysis
10:15
Results of In Vitro and In-cell SHAPE for Analyzing Small Molecule Induced Pre-mRNA Structural Changes
11:02
Conclusion
