PUS3

Existing Annotations Review

GO Term	Evidence	Action	Reason
GO:0009982 pseudouridine synthase activity	IBA GO_REF:0000033	ACCEPT	Summary: PUS3 catalyzes pseudouridine formation in tRNA as demonstrated experimentally (PMID:27055666). The IBA annotation is well-supported by evolutionary conservation of this function across the TruA/Pus3 family from bacteria to humans. Reason: This annotation accurately captures PUS3's core enzymatic function. The protein has been experimentally validated to catalyze the isomerization of uridine to pseudouridine in tRNAs, with loss-of-function mutations abolishing this activity in patient cells. Supporting Evidence: PMID:27055666 Consistent with the known role of Pus3 in isomerizing uracil to pseudouridine at positions 38 and 39 in tRNA, we found a significant reduction in this post-transcriptional modification of tRNA in patient cells.
GO:0031119 tRNA pseudouridine synthesis	IBA GO_REF:0000033	ACCEPT	Summary: PUS3 specifically synthesizes pseudouridine in tRNAs at positions 38/39 of the anticodon loop. This function is conserved across the TruA/Pus3 family and experimentally validated. Reason: This accurately describes PUS3's biological process. The enzyme specifically modifies cytosolic tRNAs, not other RNA types, as confirmed by experimental evidence showing loss of tRNA pseudouridylation in patient cells with PUS3 mutations. Supporting Evidence: PMID:27055666 PUS3 is a member of the highly conserved TruA/Pus3 family of pseudouridylases, which are important for healthy growth in bacteria and yeast...and catalyze pseudouridine formation at specific uridine residues in the anticodon-stem loop of tRNAs
GO:0005737 cytoplasm	IBA GO_REF:0000033	ACCEPT	Summary: PUS3 localizes to the cytoplasm as confirmed by multiple sources including UniProt curation and expression databases. This is consistent with its role in modifying cytosolic tRNAs. Reason: The cytoplasmic localization is well-supported. PUS3 modifies cytosolic tRNAs and needs to be present where these tRNAs function. The Human Protein Atlas and COMPARTMENTS database confirm cytoplasmic/cytosolic presence. Supporting Evidence: file:human/PUS3/PUS3-deep-research.md PUS3 predominantly localizes to the nucleus and the cytoplasm, consistent with its role in modifying tRNAs which are transcribed and processed in the nucleus and function in the cytosol file:human/PUS3/PUS3-deep-research-falcon.md PUS3 is reported as present in nucleus and cytoplasm, consistent with roles spanning nuclear pre-tRNA processing/maturation and cytoplasmic function of modified tRNAs. No retrieved evidence supported mitochondrial localization for human PUS3.
GO:0005634 nucleus	IBA GO_REF:0000033	ACCEPT	Summary: PUS3 localizes to the nucleus where it likely modifies nascent or pre-tRNAs during their maturation. This dual nuclear-cytoplasmic localization is typical for tRNA modification enzymes. Reason: Nuclear localization is well-supported by UniProt curation and expression data. PUS3 likely acts on tRNAs during their nuclear maturation phase before export to the cytoplasm. Supporting Evidence: file:human/PUS3/PUS3-uniprot.txt SUBCELLULAR LOCATION: Nucleus {ECO:0000305}.
GO:1990481 mRNA pseudouridine synthesis	IBA GO_REF:0000033	REMOVE	Summary: Recent high-throughput mapping studies found NO PUS3-dependent pseudouridine sites in mRNAs, indicating PUS3 is specific to tRNA modification and does not modify mRNAs. Reason: This annotation is incorrect based on current evidence. PUS3 specifically modifies tRNAs at positions 38/39 and has no demonstrated activity on mRNAs. Recent comprehensive mapping studies explicitly found no PUS3-dependent pseudouridine sites in mRNAs. Supporting Evidence: file:human/PUS3/PUS3-deep-research.md Notably, PUS3 activity appears specific to tRNAs; recent high-throughput mapping found no PUS3-dependent pseudouridine sites in mRNAs, linking the enzyme's function exclusively to tRNA modification file:human/PUS3/PUS3-deep-research-falcon.md Pseudo-seq in PUS3-depleted human cells found no PUS3-dependent pseudouridylation sites in mRNAs**, supporting that PUS3’s primary substrates are tRNAs rather than mRNAs.
GO:0160154 tRNA pseudouridine(38/39) synthase activity	IEA GO_REF:0000120	ACCEPT	Summary: This is the most specific and accurate molecular function annotation for PUS3, precisely describing its activity at positions 38 and 39 of tRNA anticodon loops. Reason: This highly specific term perfectly captures PUS3's enzymatic activity. It is more precise than the general pseudouridine synthase term and accurately reflects the specific positions modified by PUS3. Supporting Evidence: file:human/PUS3/PUS3-uniprot.txt RecName: Full=tRNA pseudouridine(38/39) synthase; EC=5.4.99.45
GO:0001522 pseudouridine synthesis	IEA GO_REF:0000002	MARK AS OVER ANNOTATED	Summary: While PUS3 does synthesize pseudouridine, this term is too general. The more specific term GO:0031119 (tRNA pseudouridine synthesis) better captures PUS3's specific function. Reason: This annotation is technically correct but overly general. PUS3 specifically synthesizes pseudouridine in tRNAs, not in all RNA types. The more specific GO:0031119 provides better functional information. Supporting Evidence: PMID:27055666 PUS3 is a member of the highly conserved TruA/Pus3 family of pseudouridylases...catalyze pseudouridine formation at specific uridine residues in the anticodon-stem loop of tRNAs
GO:0003723 RNA binding	IEA GO_REF:0000002	MODIFY	Summary: While PUS3 does bind RNA (specifically tRNA), this term is too vague. A more specific term like 'tRNA binding' (GO:0000049) would be more informative. Reason: PUS3 does bind RNA, but specifically binds tRNA substrates as a stand-alone enzyme. The general 'RNA binding' term doesn't convey the specificity of PUS3's substrate recognition. Proposed replacements: tRNA binding Supporting Evidence: file:human/PUS3/PUS3-deep-research.md PUS3 is a 'stand-alone' pseudouridine synthase, meaning it autonomously binds its RNA substrate without requiring a guide RNA file:human/PUS3/PUS3-deep-research-falcon.md human PUS3 has strict selectivity for intact, tRNA-shaped substrates (recognizing global tRNA architecture) and does not bind isolated anticodon stem-loop fragments efficiently.
GO:0005634 nucleus	IEA GO_REF:0000044	ACCEPT	Summary: Duplicate annotation of nuclear localization with different evidence code. The IBA annotation is sufficient. Reason: Although duplicated with the IBA annotation above, both annotations support nuclear localization which is correct for PUS3. Multiple evidence types strengthen this annotation. Supporting Evidence: file:human/PUS3/PUS3-uniprot.txt SUBCELLULAR LOCATION: Nucleus {ECO:0000305}.
GO:0008033 tRNA processing	IEA GO_REF:0000043	ACCEPT	Summary: PUS3 is involved in tRNA processing through its role in post-transcriptional modification. However, the more specific term GO:0031119 (tRNA pseudouridine synthesis) is more informative. Reason: This annotation is correct - pseudouridylation is a type of tRNA processing. PUS3 modifies tRNAs during their maturation, which is part of the broader tRNA processing pathway. Supporting Evidence: file:human/PUS3/PUS3-deep-research.md As a tRNA pseudouridine synthase, PUS3 is directly involved in tRNA processing and RNA post-transcriptional modification pathways
GO:0009451 RNA modification	IEA GO_REF:0000002	MARK AS OVER ANNOTATED	Summary: While accurate, this term is too general. PUS3 specifically performs tRNA pseudouridylation, and more specific terms are available. Reason: This annotation is correct but overly broad. PUS3 specifically modifies tRNAs by pseudouridylation. More specific terms like GO:0031119 (tRNA pseudouridine synthesis) provide better functional resolution. Supporting Evidence: PMID:27055666 identified a novel homozygous truncating mutation in PUS3 that fully segregates with the intellectual disability phenotype...found a significant reduction in this post-transcriptional modification of tRNA
GO:0009982 pseudouridine synthase activity	IEA GO_REF:0000120	ACCEPT	Summary: Duplicate of the IBA annotation for the same term. The more specific GO:0160154 (tRNA pseudouridine(38/39) synthase activity) is preferable. Reason: Correct annotation duplicating the IBA evidence above. Multiple evidence types support this core function. However, GO:0160154 provides more specificity. Supporting Evidence: PMID:27055666 Consistent with the known role of Pus3 in isomerizing uracil to pseudouridine at positions 38 and 39 in tRNA
GO:0016853 isomerase activity	IEA GO_REF:0000043	MARK AS OVER ANNOTATED	Summary: While technically correct (PUS3 is an isomerase), this term is too general. The specific pseudouridine synthase terms are more informative. Reason: This annotation is correct but far too general. PUS3 is specifically a pseudouridine synthase (RNA isomerase EC 5.4.99.45), and more specific terms accurately describe its function. Supporting Evidence: file:human/PUS3/PUS3-uniprot.txt EC=5.4.99.45...AltName: Full=tRNA-uridine isomerase 3
GO:0031119 tRNA pseudouridine synthesis	IEA GO_REF:0000120	ACCEPT	Summary: Duplicate annotation with different evidence code. Correctly describes PUS3's biological process. Reason: Correct annotation that accurately describes PUS3's role in tRNA pseudouridylation. Multiple evidence codes strengthen this annotation. Supporting Evidence: PMID:27055666 catalyze pseudouridine formation at specific uridine residues in the anticodon-stem loop of tRNAs in all kingdoms of life
GO:0006400 tRNA modification	TAS Reactome:R-HSA-8870289	ACCEPT	Summary: PUS3 performs tRNA modification through pseudouridylation at positions 38/39. This Reactome-based annotation is well-curated and accurate. Reason: Correct annotation from Reactome pathway database. PUS3's pseudouridylation activity is a specific type of tRNA modification essential for tRNA function. Supporting Evidence: file:human/PUS3/PUS3-deep-research.md PUS3 is involved in: tRNA modification – specifically pseudouridine formation in tRNAs
GO:0009982 pseudouridine synthase activity	EXP PMID:27055666 A homozygous truncating mutation in PUS3 expands the role of...	ACCEPT	Summary: Direct experimental evidence from patient cells showing loss of pseudouridine synthase activity with PUS3 mutations. This is the strongest evidence for this function. Reason: This annotation has the strongest experimental support. The cited paper directly demonstrated that PUS3 mutations result in loss of tRNA pseudouridylation in patient cells. Supporting Evidence: PMID:27055666 we found a significant reduction in this post-transcriptional modification of tRNA in patient cells...Since tRNA Phe from LCLs with the Arg435* allele of PUS3 had almost exactly 1 mole/mole less Ψ than control LCLs
GO:0160154 tRNA pseudouridine(38/39) synthase activity	IMP PMID:27055666 A homozygous truncating mutation in PUS3 expands the role of...	ACCEPT	Summary: The most specific and accurate molecular function for PUS3, with strong mutant phenotype evidence showing loss of pseudouridine at positions 38/39 in patient tRNAs. Reason: This is the most precise annotation for PUS3's molecular function, supported by direct evidence from mutant phenotypes. Patient cells with PUS3 mutations specifically lose pseudouridine at these positions. Supporting Evidence: PMID:27055666 Consistent with the known role of Pus3 in isomerizing uracil to pseudouridine at positions 38 and 39 in tRNA, we found a significant reduction in this post-transcriptional modification of tRNA in patient cells file:human/PUS3/PUS3-deep-research-falcon.md A primary biochemical study using recombinant human PUS3 shows direct catalysis of tRNA Ψ39 formation in vitro using CMC-based primer extension assays.
GO:0031119 tRNA pseudouridine synthesis	IMP PMID:27055666 A homozygous truncating mutation in PUS3 expands the role of...	ACCEPT	Summary: Strong experimental evidence from mutant phenotypes showing loss of tRNA pseudouridylation. This accurately describes PUS3's biological process. Reason: Well-supported by mutant phenotype data showing that loss of PUS3 function results in decreased tRNA pseudouridylation, confirming its role in this biological process. Supporting Evidence: PMID:27055666 we show that a homozygous truncation mutation in PUS3 segregating with ID results in impaired isomerization of uridine to pseudouridine (Ψ) in patient tRNA
GO:0005829 cytosol	TAS Reactome:R-HSA-8870289	ACCEPT	Summary: PUS3 localizes to the cytosol where it modifies cytosolic tRNAs. This Reactome-based annotation is consistent with other localization data. Reason: Correct annotation from curated Reactome pathway. PUS3 acts on cytosolic tRNAs and is detected in the cytosolic fraction, distinguishing it from mitochondrial pseudouridine synthases. Supporting Evidence: file:human/PUS3/PUS3-deep-research.md The COMPARTMENTS database (integrating multiple localization evidence) likewise scores PUS3 highest for the cytosol and nucleus (confidence scores 5 and 4, respectively)