GO:0160154 tRNA pseudouridine(38/39) synthase activity: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0160154 describes the molecular function of catalyzing the conversion of uridine at positions 38 and/or 39 of tRNA into pseudouridine, a conserved RNA modification.
• This activity is essential for proper tRNA folding and function, impacting translation fidelity and efficiency.
• The human enzyme responsible, PUS3 (pseudouridine synthase 3), selectively modifies tRNA positions 38/39 and is linked to neurological disorders.
• Key catalytic residues, including a conserved aspartate, are critical for the isomerization reaction.
• Dysregulation of tRNA pseudouridylation is associated with cancer, neurodegeneration, and mitochondrial diseases.
• CRISPR-based models (knockout, point mutation, knock-in) enable precise functional studies of this modification and its role in disease.
Description
tRNA pseudouridine(38/39) synthase activity (GO:0160154) is a molecular function that introduces pseudouridine (Ψ) at positions 38 and/or 39 of transfer RNA (tRNA). This modification is one of the most abundant in tRNA and is critical for stabilizing the canonical L-shaped tertiary structure, thereby influencing translation accuracy and efficiency. The enzyme responsible in humans, PUS3, belongs to the pseudouridine synthase family and exhibits strict substrate specificity for tRNA. Understanding this activity is fundamental for researchers studying RNA modification, translation, and related diseases.
tRNA pseudouridine(38/39) synthase activity At A Glance
| GO ID | GO:0160154 |
|---|---|
| GO term | tRNA pseudouridine(38/39) synthase activity |
| Ontology | molecular_function |
| Synonym | None |
| Major function | Catalyzes the isomerization of uridine to pseudouridine at positions 38 and/or 39 in tRNA |
| Reaction | uridine(38/39) in tRNA = pseudouridine(38/39) in tRNA |
| Substrate | tRNA containing uridine at position 38 and/or 39 |
| Product | tRNA containing pseudouridine at position 38 and/or 39 |
| Cofactors | None required (uses conserved aspartate as nucleophile) |
What Is GO:0160154?
GO:0160154 is defined as the catalysis of the reaction: uridine(38/39) in tRNA = pseudouridine(38/39) in tRNA. It specifically modifies uridine at position 38 and/or 39 of tRNA molecules, converting it to pseudouridine through an isomerization reaction.
Why Is tRNA pseudouridine(38/39) synthase activity Important in Cell Biology?
Pseudouridylation at tRNA positions 38/39 is crucial for maintaining the structural integrity and function of tRNA, which directly affects protein synthesis. Mutations in the human enzyme PUS3 cause intellectual disability and other neurological phenotypes, highlighting its clinical relevance. Moreover, this modification is implicated in cancer progression and mitochondrial dysfunction, making it a potential therapeutic target.
• Essential for tRNA stability and folding, impacting translation.
• Mutations in PUS3 lead to neurodevelopmental disorders.
• Altered pseudouridylation is observed in various cancers.
• Plays a role in mitochondrial tRNA modification and related diseases.
• Conserved from bacteria to humans, facilitating model organism studies.
• Provides a paradigm for understanding RNA-modifying enzyme mechanisms.
• Potential biomarker for disease diagnosis and prognosis.
• Target for RNA-based therapeutics and drug discovery.
Molecular Mechanism of tRNA pseudouridine(38/39) synthase activity
Substrate Recognition and Binding
In simple terms: The enzyme finds and grabs the tRNA molecule at the right spot.
The synthase specifically recognizes the anticodon arm of tRNA, particularly the region around positions 38 and 39. Structural studies of TruA, a bacterial homolog, reveal that the enzyme binds tRNA through conserved residues that interact with the anticodon stem-loop, ensuring precise positioning of the target uridine. Human PUS3 also exhibits strict tRNA selectivity, as shown by recent molecular analyses.
Catalytic Isomerization
In simple terms: The enzyme changes uridine into pseudouridine by rearranging its atoms.
The isomerization of uridine to pseudouridine involves cleavage of the glycosidic bond, rotation of the base, and re-ligation. A conserved aspartate residue acts as a nucleophile, forming a covalent intermediate with the ribose, as demonstrated for pseudouridine synthase I. Cysteine residues are also implicated in the rearrangement process, though their exact role may vary among enzymes.
Cofactors and Energy Requirements
In simple terms: No extra molecules are needed; the enzyme does the job on its own.
Unlike many RNA-modifying enzymes, tRNA pseudouridine synthases do not require ATP or other cofactors. The reaction is driven by the intrinsic chemistry of the active site, with the conserved aspartate facilitating the rearrangement without external energy sources.
Regulation and Post-Translational Modifications
In simple terms: The enzyme's activity can be turned up or down by cellular signals.
While direct regulation of PUS3 is not fully elucidated, its expression and activity may be influenced by cellular stress and metabolic states. For instance, pseudouridylation levels can change in response to environmental cues, potentially affecting translation under stress conditions.
Key Genes Involved in GO:0160154 tRNA pseudouridine(38/39) synthase activity
The following genes and proteins are key players in tRNA pseudouridine(38/39) synthase activity and its biological context.
| Gene | Major Role | Research Relevance |
|---|---|---|
| PUS3 | Human tRNA pseudouridine(38/39) synthase; catalyzes Ψ38/39 formation | Mutations linked to neurodevelopmental disorders; target for cancer studies |
| PUS1 | Pseudouridine synthase acting on tRNA and other RNAs | Related to mitochondrial myopathy and sideroblastic anemia |
| DKC1 | Pseudouridine synthase in H/ACA snoRNPs | Dyskeratosis congenita; telomere maintenance |
| TRUA (TruA) | Bacterial homolog; modifies tRNA positions 38/39 | Model for structural and mechanistic studies |
| RluA | Bacterial pseudouridine synthase for 23S rRNA and tRNA | Insights into substrate specificity |
| PUS7 | Pseudouridine synthase for tRNA and other RNAs | Role in stem cell differentiation and cancer |
| PUS10 | Pseudouridine synthase involved in tRNA and miRNA processing | Implicated in apoptosis and cancer |
| PUS4 | tRNA pseudouridine synthase for position 55 | Distinct from 38/39 but related family member |
| PUS6 | Mitochondrial tRNA pseudouridine synthase | Mitochondrial translation and disease |
| PUS7L | Pseudouridine synthase-like protein | Less characterized; potential regulatory roles |
| PUS3 (zebrafish) | Model organism ortholog | Developmental studies and disease modeling |
| PUS3 (mouse) | Mammalian model for PUS3 function | Neurological and behavioral studies |
| tRNA | Substrate for modification | Central to translation and its regulation |
| Anticodon stem-loop | Structural element recognized by synthase | Key for substrate specificity |
| Aspartate residue (catalytic) | Essential for isomerization | Mutational analysis target |
| Cysteine residues | Potential role in catalysis | Biochemical studies |
| PUS1 (yeast) | Yeast ortholog for pseudouridylation | Genetic screens and functional studies |
| PUS3 (Drosophila) | Invertebrate model | Developmental genetics |
How Is tRNA pseudouridine(38/39) synthase activity Regulated?
The activity of tRNA pseudouridine(38/39) synthase is primarily regulated at the level of enzyme expression and substrate availability. While no direct allosteric regulators are known, cellular stress conditions can alter pseudouridylation patterns, potentially through changes in PUS3 expression or tRNA modifications. Additionally, mutations in the catalytic domain, such as the conserved aspartate, abolish activity, underscoring the importance of structural integrity for regulation.
tRNA pseudouridine(38/39) synthase activity and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| PUS3 | Neurodevelopmental disorder with intellectual disability | Knockout mouse, patient-derived iPSCs |
| PUS3 | Cancer (various types) | Cancer cell lines with PUS3 knockdown/overexpression |
| PUS1 | Mitochondrial myopathy and sideroblastic anemia | Yeast and human cell models |
| DKC1 | Dyskeratosis congenita | Patient fibroblasts, zebrafish |
| PUS7 | Stem cell differentiation defects | Embryonic stem cells |
Neurological Disorders
Biallelic mutations in PUS3 cause a neurodevelopmental disorder characterized by intellectual disability, microcephaly, and seizures. These mutations often affect the catalytic domain, leading to loss of pseudouridylation at tRNA positions 38/39 and impaired translation in neurons.
Cancer
Dysregulated pseudouridylation is emerging as a hallmark of cancer. PUS3 expression is altered in various malignancies, and its activity may influence tumor growth and progression through effects on translation and stress responses.
Mitochondrial Diseases
Although PUS3 primarily modifies cytoplasmic tRNA, other pseudouridine synthases like PUS6 modify mitochondrial tRNA. Defects in mitochondrial pseudouridylation can lead to oxidative phosphorylation deficiencies and mitochondrial myopathies.
From tRNA pseudouridine(38/39) synthase activity-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| What is the effect of PUS3 loss on translation? | PUS3 knockout cell lines (e.g., HEK293T) |
| How does a specific point mutation affect catalytic activity? | Point-mutation knock-in via CRISPR (e.g., D→A) |
| Does tagging PUS3 alter its localization? | Knock-in of fluorescent tag (e.g., GFP) |
| Can overexpression rescue a disease phenotype? | Overexpression of wild-type PUS3 in patient cells |
| What is the substrate specificity of PUS3? | In vitro assays with mutant tRNA substrates |
| How does PUS3 mutation affect neuronal development? | Patient iPSC-derived neurons |
How to Study the tRNA pseudouridine(38/39) synthase activity Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Ribo-seq | Translation efficiency and ribosome occupancy | Assessing impact of PUS3 loss on global translation |
| Ψ-seq | Pseudouridine sites transcriptome-wide | Mapping tRNA modifications |
| CRISPR knockout | Loss of gene function | Studying PUS3 essentiality |
| Site-directed mutagenesis | Effect of specific amino acid changes | Testing catalytic residues |
| X-ray crystallography | 3D structure of enzyme-tRNA complex | Understanding substrate binding |
| HPLC/MS | Quantification of pseudouridine | Measuring enzyme activity in vitro |
| Western blot | Protein expression levels | Validating knockout/overexpression |
| Immunofluorescence | Subcellular localization | Determining PUS3 localization |
Ribo-seq and RNA-seq
Ribosome profiling (Ribo-seq) can measure changes in translation efficiency upon PUS3 perturbation, while RNA-seq reveals transcript-level effects. These methods help link pseudouridylation to codon-specific translation defects.
Pseudouridine Detection
Pseudouridine can be detected using Ψ-seq, which involves chemical modification (CMC) followed by sequencing. This allows mapping of pseudouridylation sites at single-nucleotide resolution, including positions 38/39 in tRNA.
Structural Biology
X-ray crystallography and cryo-EM of PUS3-tRNA complexes provide insights into substrate recognition and catalysis. The structure of TruA from Thermus thermophilus revealed key interactions with the anticodon stem-loop.
Biochemical Assays
In vitro assays using purified enzyme and tRNA substrates, combined with mutagenesis of catalytic residues (e.g., aspartate), can dissect the mechanism. High-performance liquid chromatography (HPLC) or mass spectrometry can quantify pseudouridine formation.
How CRISPR Can Be Used to Study GO:0160154 tRNA pseudouridine(38/39) synthase activity
Knockout
CRISPR-Cas9 knockout of PUS3 in cell lines (e.g., HEK293T, HeLa) abolishes pseudouridylation at positions 38/39, leading to tRNA instability and translation defects. These models are valuable for studying the cellular consequences of loss of function.
Point Mutation
Introducing point mutations in the catalytic domain of PUS3 (e.g., aspartate to alanine) via CRISPR base editing or HDR allows precise dissection of the enzymatic mechanism without affecting protein stability. Such models can reveal the importance of individual residues.
Knock-in
Knock-in of epitope tags (e.g., FLAG, GFP) at the endogenous PUS3 locus enables tracking of protein expression, localization, and interaction partners in a physiological context. This approach avoids artifacts from overexpression.
Overexpression
CRISPR activation (CRISPRa) or lentiviral overexpression of PUS3 can be used to study gain-of-function effects, such as enhanced pseudouridylation and its impact on translation and cell growth. Overexpression models are useful for rescue experiments.
How EDITGENE Supports tRNA pseudouridine(38/39) synthase activity Research
Researchers studying tRNA pseudouridine(38/39) synthase activity-related genes often need to determine whether a candidate gene is causally involved in a specific phenotype, such as translation defects or disease progression. EDITGENE provides a comprehensive suite of CRISPR-based services to generate precisely engineered cell models, enabling rigorous functional validation.
Contact EDITGENE today to design your custom CRISPR model for tRNA pseudouridine(38/39) synthase activity research.
Frequently Asked Questions About tRNA pseudouridine(38/39) synthase activity
What is tRNA pseudouridine(38/39) synthase activity?
It is the enzymatic activity that converts uridine at positions 38 and/or 39 of tRNA into pseudouridine, a modified RNA base critical for tRNA structure and function.
What genes are involved in tRNA pseudouridine(38/39) synthase activity?
The primary human gene is PUS3, which encodes the enzyme responsible for this modification. Homologs include TruA in bacteria and PUS1 in yeast.
What diseases are associated with tRNA pseudouridine(38/39) synthase activity?
Mutations in PUS3 cause neurodevelopmental disorders with intellectual disability. Dysregulation is also implicated in cancer and mitochondrial diseases.
How is tRNA pseudouridine(38/39) synthase activity regulated?
Regulation occurs mainly through enzyme expression and substrate availability. Cellular stress can alter pseudouridylation patterns.
What is the mechanism of tRNA pseudouridine(38/39) synthase?
The enzyme uses a conserved aspartate as a nucleophile to isomerize uridine to pseudouridine, without requiring cofactors.
Can CRISPR be used to study tRNA pseudouridine(38/39) synthase activity?
Yes, CRISPR knockout, point mutation, knock-in, and overexpression models enable precise functional studies of PUS3 and its role in translation and disease.
What methods detect pseudouridine in tRNA?
Ψ-seq, HPLC, and mass spectrometry are commonly used to detect and quantify pseudouridine at specific tRNA positions.
Why is pseudouridine at position 38/39 important?
It stabilizes the anticodon loop structure, ensuring accurate and efficient translation.
Is PUS3 essential for survival?
PUS3 is essential for normal development; its loss causes severe neurological phenotypes in humans and model organisms.
How can I create a PUS3 knockout cell line?
EDITGENE provides custom CRISPR knockout services to generate PUS3 knockout cell lines for functional studies.
Conclusion
tRNA pseudouridine(38/39) synthase activity (GO:0160154) is a fundamental RNA modification process that ensures proper tRNA function and translation. The human enzyme PUS3 is critical for this activity, and its dysfunction leads to neurological disorders and contributes to cancer. Understanding the molecular mechanism and regulation of this enzyme opens avenues for therapeutic intervention. CRISPR-based models and advanced sequencing methods are indispensable tools for dissecting its roles in health and disease.
References
- 1. Lin TY et al.. 2024. The molecular basis of tRNA selectivity by human pseudouridine synthase 3.. Mol Cell 84(13):2472-2489.e8 PMID: 38996458
- 2. Dong X et al.. 2006. Crystal structure of tRNA pseudouridine synthase TruA from Thermus thermophilus HB8.. RNA Biol 3(3):115-22 PMID: 17114947
- 3. Green CJ et al.. 1982. Purification and properties of a mammalian tRNA pseudouridine synthase.. J Biol Chem 257(6):3045-52 PMID: 7037778
- 4. Huang L et al.. 1998. A conserved aspartate of tRNA pseudouridine synthase is essential for activity and a probable nucleophilic catalyst.. Biochemistry 37(1):344-51 PMID: 9425056
- 5. Zhao X et al.. 1997. The role of cysteine residues in the rearrangement of uridine to pseudouridine catalyzed by pseudouridine synthase I.. J Biol Chem 272(3):1950-5 PMID: 8999885
