GO:0002143 tRNA wobble position uridine thiolation: Translational Fidelity Pathway, Genes, Functions and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0002143 describes the post-transcriptional conversion of uridine at tRNA anticodon position 34 into 2-thiouridine (s2U), a sulfur-transfer process that requires L-cysteine as the sulfur donor.
• The conserved Ctu1-Ctu2 (also known as Ncs6-Ncs2) thiolase complex is the core enzymatic machinery that catalyzes wobble uridine thiolation in eukaryotes.
• Loss of wobble uridine thiolation impairs ribosome A-site binding of tKUUU, tQUUG and tEUUC, reducing translational efficiency and fidelity.
• Biallelic variants in CTU2 cause DREAM-PL syndrome, a human developmental disorder directly linked to defective tRNA wobble U34 thiolation.
• Wobble uridine thiolation is required for genome integrity and is connected to additional modifications such as mcm5s2U and yW that depend on ALKBH8 and Sod1.
• CRISPR knockout, point-mutation, knock-in and overexpression models enable causal dissection of thiolation pathway genes in development, angiogenesis and disease.
Description
GO:0002143, tRNA wobble position uridine thiolation, is the biological process in which a uridine residue at position 34 of a tRNA anticodon is post-transcriptionally thiolated at the C2 position, using sulfur transferred from L-cysteine through several enzymatic steps. This modification produces 2-thiouridine (s2U) and related derivatives at the wobble position, where codon-anticodon pairing occurs. Because wobble nucleotides govern how tRNAs recognize degenerate codons, thiolation directly influences the speed and accuracy of protein synthesis. The process is conserved from yeast to humans, and its core enzymes, Ctu1 and Ctu2, form a thiolase complex that is essential for normal development and genome stability. In recent years, human genetics has linked defects in this pathway to DREAM-PL syndrome, a severe developmental disorder caused by biallelic CTU2 variants that impair U34 thiolation. Consequently, GO:0002143 has become a focal point for researchers studying translation, tRNA biology, developmental disease and genome maintenance.
tRNA wobble position uridine thiolation At A Glance
| GO ID | GO:0002143 |
|---|---|
| GO term | tRNA wobble position uridine thiolation |
| Ontology | biological_process |
| Synonym | tRNA wobble uridine thiolation; wobble position s2U biosynthesis |
| Major function | Post-transcriptional thiolation of uridine 34 in tRNA anticodons to form 2-thiouridine, supporting codon recognition and translation |
| Sulfur donor | L-cysteine |
| Core enzyme complex | Ctu1-Ctu2 (Ncs6-Ncs2) thiolase |
| Key modified tRNAs | tKUUU, tQUUG, tEUUC |
| Associated human disease | DREAM-PL syndrome (CTU2 variants) |
What Is GO:0002143?
In simple terms, GO:0002143 is the cellular process that attaches a sulfur atom to a specific uridine in tRNA so the tRNA can decode its codons correctly. More precisely, it is the post-transcriptional thiolation of the uridine at position 34 of the anticodon, generating 2-thiouridine through a multi-step transfer of sulfur from L-cysteine. This wobble-position modification is distinct from other tRNA modifications and is required for efficient codon recognition and translational fidelity.
Why Is tRNA wobble position uridine thiolation Important in Cell Biology?
Wobble uridine thiolation is important because it chemically tunes the tRNA anticodon loop to ensure accurate and efficient decoding of mRNA codons, and its disruption has measurable consequences for translation, genome stability and organismal development. The pathway is conserved and essential, and mutations in its components cause human disease, making it a high-value target for mechanistic and translational research.
• Ensures efficient ribosome A-site binding for tRNAs with U34 modifications, directly affecting translation rate.
• Maintains translational fidelity by stabilizing codon-anticodon interactions at the wobble position.
• Required for genome integrity, as loss of Ctu1-Ctu2 thiolase activity increases genome instability.
• Essential for angiogenesis and embryonic development in vertebrate models.
• Causally linked to DREAM-PL syndrome through biallelic CTU2 variants.
• Interconnects with other tRNA modifications such as mcm5s2U and yW, which depend on ALKBH8 and Sod1.
• Provides a model system for studying tRNA modification enzymes and their E1-like activation by Uba4.
• Relevant to Leishmania tRNA sorting and subcellular localization studies.
• Offers CRISPR-tractable targets for functional genomics of translation.
• Serves as a biomarker candidate for disorders of tRNA modification and translation.
What Happens During tRNA wobble position uridine thiolation?
Substrate recognition and sulfur transfer from L-cysteine
In simple terms: The cell takes sulfur from the amino acid cysteine and prepares it for attachment to tRNA.
The thiolation process begins with the transfer of sulfur from L-cysteine to the tRNA uridine 34 substrate through several enzymatic steps. This step is chemically demanding and requires dedicated enzymes to mobilize the sulfur donor and deliver it to the tRNA.
Activation by the Uba4 E1-like enzyme
In simple terms: A helper enzyme activates the sulfur-carrying protein so it can pass sulfur onward.
The E1-activating enzyme Uba4 activates Urm1 by thiocarboxylation, a key step that enables sulfur relay to the thiolation machinery. Structural and biochemical studies have revealed the molecular basis for thiocarboxylation and release of Urm1 by Uba4, clarifying how sulfur is handed off in the pathway.
Ctu1-Ctu2 thiolase complex catalyzes U34 thiolation
In simple terms: A two-protein machine called Ctu1-Ctu2 puts the sulfur onto the tRNA.
The conserved wobble uridine tRNA thiolase Ctu1-Ctu2 is required for the thiolation of U34 and for maintaining genome integrity. In vertebrate models, Ctu1 is required for angiogenesis and embryonic development, demonstrating that the thiolase complex is essential for normal organismal physiology.
Formation of 2-thiouridine and related wobble modifications
In simple terms: The final product is a modified tRNA base called 2-thiouridine that helps the tRNA read its codon.
Thiolation at C2 of uridine 34 generates 2-thiouridine (s2U), which is further elaborated into complex wobble modifications such as mcm5s2U. ALKBH8 contributes methyltransferase activity required for the biogenesis of multiple wobble uridine modifications, linking thiolation to a broader modification network. Sod1 deficiency impairs formation of mcm5s2U and yW, indicating that redox homeostasis influences this pathway.
Functional consequence: enhanced ribosome A-site binding
In simple terms: The modified tRNA binds the ribosome better, so proteins are made more accurately.
tRNA tKUUU, tQUUG and tEUUC wobble position modifications fine-tune protein translation by promoting ribosome A-site binding. This functional readout explains why loss of thiolation reduces translational efficiency and fidelity.
Key Genes Involved in GO:0002143 tRNA wobble position uridine thiolation
The following genes and proteins are experimentally implicated in tRNA wobble position uridine thiolation and its associated biology.
| Gene | Major Role | Research Relevance |
|---|---|---|
| CTU1 | Core subunit of the Ctu1-Ctu2 thiolase complex that catalyzes U34 thiolation | Required for angiogenesis and embryonic development; knockout models show developmental defects |
| CTU2 | Core subunit of the thiolase complex; biallelic variants impair U34 thiolation | Causally linked to DREAM-PL syndrome; key disease gene |
| UBA4 | E1-activating enzyme that thiocarboxylates Urm1 to mobilize sulfur | Provides mechanistic entry point for sulfur relay studies |
| URM1 | Sulfur carrier protein activated by Uba4 | Central to understanding sulfur transfer in thiolation |
| ALKBH8 | tRNA methyltransferase required for biogenesis of multiple wobble uridine modifications | Links thiolation to broader wobble modification networks |
| SOD1 | Redox enzyme whose deficiency impairs mcm5s2U and yW formation | Connects oxidative stress to tRNA modification |
| tKUUU (tRNA-Lys) | Wobble-modified tRNA whose A-site binding depends on thiolation | Functional readout for translation studies |
| tQUUG (tRNA-Gln) | Wobble-modified tRNA with thiolation-dependent decoding | Model tRNA for codon-specific translation assays |
| tEUUC (tRNA-Glu) | Wobble-modified tRNA requiring thiolation for efficient A-site binding | Used to dissect wobble modification effects |
| NCS6 (yeast CTU1 ortholog) | Yeast thiolase subunit required for genome integrity | Genetic model for thiolation pathway |
| NCS2 (yeast CTU2 ortholog) | Yeast thiolase subunit required for genome integrity | Genetic model for thiolation pathway |
| Leishmania tRNA genes | tRNAs whose wobble modifications differ and influence subcellular localization | Comparative model for tRNA sorting |
How Is tRNA wobble position uridine thiolation Regulated?
The thiolation pathway is regulated at the level of sulfur mobilization and enzyme availability. Uba4-mediated thiocarboxylation of Urm1 is a regulated activation step that controls sulfur flux into the pathway. In addition, redox status influences the formation of downstream wobble modifications, as Sod1 deficiency impairs mcm5s2U and yW production. ALKBH8-dependent methylation further modulates the spectrum of wobble uridine modifications, indicating layered regulation of the pathway.
tRNA wobble position uridine thiolation and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| CTU2 | DREAM-PL syndrome with impaired U34 thiolation | Patient-derived cells or CTU2 point-mutation knock-in models |
| CTU1 | Angiogenesis and embryonic development defects | Zebrafish or mouse Ctu1 knockout |
| CTU1/CTU2 | Genome instability | Yeast ncs6/ncs2 deletion and mammalian knockout cells |
| ALKBH8 | Wobble modification biogenesis defects | ALKBH8 knockout cell lines |
| SOD1 | Impaired mcm5s2U and yW formation under redox stress | Sod1-deficient cells and overexpression rescue |
DREAM-PL syndrome and CTU2 variants
Biallelic variants in CTU2 cause DREAM-PL syndrome and impair thiolation of tRNA wobble U34, establishing a direct link between this GO process and a human developmental disorder. This finding makes CTU2 a diagnostic and mechanistic focal point for tRNA modification diseases.
Genome instability and cancer biology
The conserved wobble uridine tRNA thiolase Ctu1-Ctu2 is required to maintain genome integrity, suggesting that loss of thiolation could contribute to genomic instability relevant to cancer. This connection positions the pathway as a candidate for studies of DNA damage and tumorigenesis.
Developmental and angiogenic defects
The conserved wobble uridine tRNA thiolase Ctu1 is required for angiogenesis and embryonic development, indicating that thiolation defects can disrupt vascular and embryonic programs. These observations support the use of vertebrate models to study the developmental impact of thiolation loss.
Neurodegeneration and redox stress
Sod1-deficient cells are impaired in formation of the modified nucleosides mcm5s2U and yW in tRNA, linking redox stress and neurodegeneration-associated pathways to wobble modification defects. This suggests that thiolation-related modifications may be relevant to oxidative stress-related disease.
From tRNA wobble position uridine thiolation-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Is CTU1 required for development? | CTU1 knockout zebrafish or mouse |
| Do CTU2 variants impair U34 thiolation? | CTU2 point-mutation knock-in cell lines |
| How does Uba4 activate Urm1? | Recombinant Uba4/Urm1 biochemistry with tagged knock-in |
| Does thiolation affect translation fidelity? | Knockout cells analyzed by Ribo-seq and polysome profiling |
| Does loss of thiolation cause genome instability? | Yeast ncs6/ncs2 deletion and mammalian KO |
| Can ALKBH8 or Sod1 rescue modification defects? | Overexpression and rescue models |
How to Study the tRNA wobble position uridine thiolation Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Ribo-seq | Ribosome occupancy and translation efficiency | Assessing translational impact of thiolation loss |
| Polysome profiling | Global translation status | Validating translation defects in knockout cells |
| LC-MS nucleoside analysis | Levels of s2U, mcm5s2U and yW | Quantifying wobble modification defects |
| Biochemical thiocarboxylation assay | Uba4-mediated Urm1 activation | Mechanistic studies of sulfur transfer |
| Yeast genetics | Genome integrity and growth phenotypes | Functional conservation studies |
| Zebrafish developmental imaging | Angiogenesis and embryonic phenotypes | In vivo relevance of thiolation |
| Fluorescence in situ hybridization | tRNA subcellular localization | Comparative tRNA sorting studies |
Ribo-seq and polysome profiling
Ribosome profiling measures ribosome occupancy and can reveal translation defects when wobble uridine thiolation is lost, because modified tRNAs promote A-site binding. Polysome profiling complements this by assessing global translation efficiency.
tRNA modification analysis by mass spectrometry
Mass spectrometry-based nucleoside analysis detects 2-thiouridine and related modifications such as mcm5s2U, allowing direct quantification of pathway activity. This approach is essential for validating thiolation defects in mutant cells.
Genetic and biochemical assays of sulfur transfer
Biochemical reconstitution of Uba4-mediated thiocarboxylation and Urm1 release provides mechanistic insight into sulfur relay. Genetic deletion of Ctu1-Ctu2 in yeast and mammalian cells links enzyme activity to genome integrity.
Developmental and imaging assays
Vertebrate models can be used to assess angiogenesis and embryonic development upon loss of Ctu1, combining imaging with molecular readouts. Comparative tRNA localization studies in Leishmania provide additional cell biology context.
How CRISPR Can Be Used to Study GO:0002143 tRNA wobble position uridine thiolation
Knockout
CRISPR knockout of CTU1 or CTU2 abolishes wobble uridine thiolation and produces measurable translation and genome stability phenotypes, enabling causal testing of the pathway. Knockout models are also useful for validating disease-associated variants.
Point Mutation
Introducing patient-derived CTU2 point mutations by CRISPR allows precise modeling of DREAM-PL syndrome and assessment of U34 thiolation defects. Point-mutation models are ideal for separating catalytic from structural functions of thiolase subunits.
Knock-in
Tagged knock-in of CTU1, CTU2, UBA4 or URM1 supports biochemical purification and localization studies of the thiolation machinery. Knock-in reporters can also track pathway activity in living cells.
Overexpression
Overexpression of ALKBH8 or Sod1 can be used to test rescue of wobble modification defects and to probe regulatory interactions. Overexpression models help define sufficiency of individual components in the pathway.
How EDITGENE Supports tRNA wobble position uridine thiolation Research
Researchers studying tRNA wobble position uridine thiolation-related genes often need to determine whether a candidate gene is causally involved in the pathway or merely correlated with its phenotypes. EDITGENE provides the CRISPR tools and bioinformatics support required to move from correlation to causation in this conserved translational process.
Contact EDITGENE today to design your custom CRISPR model for tRNA wobble position uridine thiolation research.
Frequently Asked Questions About tRNA wobble position uridine thiolation
What is tRNA wobble position uridine thiolation?
It is the post-transcriptional conversion of uridine 34 in tRNA anticodons into 2-thiouridine using sulfur from L-cysteine, a process defined by GO:0002143.
What genes are involved in tRNA wobble position uridine thiolation?
Key genes include CTU1, CTU2, UBA4, URM1, ALKBH8 and SOD1, which together support sulfur transfer and wobble modification.
Why is wobble uridine thiolation important for translation?
It promotes ribosome A-site binding of tRNAs such as tKUUU, tQUUG and tEUUC, improving translational efficiency and fidelity.
What disease is linked to CTU2 mutations?
Biallelic CTU2 variants cause DREAM-PL syndrome and impair thiolation of tRNA wobble U34.
How is 2-thiouridine formed?
Sulfur is transferred from L-cysteine through several steps, including Uba4-mediated activation of Urm1 and catalysis by the Ctu1-Ctu2 thiolase.
Does loss of thiolation affect genome stability?
Yes, the conserved Ctu1-Ctu2 thiolase is required to maintain genome integrity.
What methods study tRNA wobble uridine thiolation?
Ribo-seq, polysome profiling, LC-MS nucleoside analysis and biochemical thiocarboxylation assays are commonly used.
Is wobble uridine thiolation conserved?
Yes, the Ctu1-Ctu2 thiolase is conserved and is required for development and genome integrity across species.
How does Sod1 relate to wobble modifications?
Sod1-deficient cells are impaired in formation of mcm5s2U and yW, linking redox status to wobble modification.
Can CRISPR model thiolation pathway defects?
Yes, CRISPR knockout, point-mutation, knock-in and overexpression models enable causal studies of CTU1, CTU2 and related genes.
Conclusion
GO:0002143, tRNA wobble position uridine thiolation, is a conserved and mechanistically rich process that converts uridine 34 into 2-thiouridine to support accurate translation. Its core enzymes, Ctu1 and Ctu2, are required for genome integrity and development, and CTU2 variants cause DREAM-PL syndrome in humans. Studying this pathway with CRISPR models and multi-omics methods will continue to reveal how tRNA modifications shape translation and disease.
References
- 1. Yu Y et al.. 2024. The conserved wobble uridine tRNA thiolase Ctu1 is required for angiogenesis and embryonic development.. PLoS One 19(12):e0315854 PMID: 39705244
- 2. Sokołowski M et al.. 2024. Molecular basis for thiocarboxylation and release of Urm1 by its E1-activating enzyme Uba4.. Nucleic Acids Res 52(22):13980-13995 PMID: 39673271
- 3. Shaheen R et al.. 2019. Biallelic variants in CTU2 cause DREAM-PL syndrome and impair thiolation of tRNA wobble U34.. Hum Mutat 40(11):2108-2120 PMID: 31301155
- 4. Rezgui VA et al.. 2013. tRNA tKUUU, tQUUG, and tEUUC wobble position modifications fine-tune protein translation by promoting ribosome A-site binding.. Proc Natl Acad Sci U S A 110(30):12289-94 PMID: 23836657
- 5. Dewez M et al.. 2008. The conserved Wobble uridine tRNA thiolase Ctu1-Ctu2 is required to maintain genome integrity.. Proc Natl Acad Sci U S A 105(14):5459-64 PMID: 18391219
- 6. Songe-Møller L et al.. 2010. Mammalian ALKBH8 possesses tRNA methyltransferase activity required for the biogenesis of multiple wobble uridine modifications implicated in translational decoding.. Mol Cell Biol 30(7):1814-27 PMID: 20123966
- 7. Xu F et al.. 2024. Sod1-deficient cells are impaired in formation of the modified nucleosides mcm(5)s(2)U and yW in tRNA.. RNA 30(12):1586-1595 PMID: 39322276
- 8. Kaneko T et al.. 2003. Wobble modification differences and subcellular localization of tRNAs in Leishmania tarentolae: implication for tRNA sorting mechanism.. EMBO J 22(3):657-67 PMID: 12554666
