| Aspect | Key findings (1–2 sentences) | Key quantitative/statistical data | Key sources (with DOI URL; publication date) | Evidence type |
|---|---|---|---|---|
| Reaction/site | Human PUS3 is the correct UniProt Q9BZE2 gene product and is a TruA-family stand-alone pseudouridine synthase that catalyzes uridine-to-pseudouridine formation in the tRNA anticodon stem-loop, primarily at positions 38/39; recombinant human PUS3 directly catalyzes Ψ39 formation in vitro. This matches the UniProt annotation for “tRNA pseudouridine(38/39) synthase.” (pqac-00000017, pqac-00000022, pqac-00000027) | In vitro tRNA-binding EC50 for WT PUS3: 3.7 ± 0.6 μM; Y71C: 2.6 ± 0.7 μM. Thermal stability Tm: WT 51.4 ± 0.1 °C; catalytic-dead D118A 52.8 ± 0.1 °C; Y71C 40.1 ± 0.1 °C. (pqac-00000018) | Lin 2022, *Human Mutation*, Oct 2022, https://doi.org/10.1002/humu.24471; Lin 2025, *RNA Biology*, 2025, https://doi.org/10.1080/15476286.2025.2541421 | Biochemical; mechanistic review |
| Substrates/specificity | Human PUS3 shows strict preference for intact tRNA-shaped substrates rather than isolated anticodon stem-loops; both mature and precursor tRNAs can bind. A 2025 mechanistic review reports that Pseudo-seq in PUS3-depleted human cells detected no PUS3-dependent mRNA sites, supporting primarily tRNA-specific activity, whereas older reviews listed tRNA and mRNA more broadly. (pqac-00000023, pqac-00000016, pqac-00000025) | Qualitative rather than kinetic in the cited review: no detectable PUS3-dependent mRNA Ψ sites by Pseudo-seq in human cells; substrate recognition requires intact tRNA architecture. (pqac-00000023) | Lin 2025, *RNA Biology*, 2025, https://doi.org/10.1080/15476286.2025.2541421; Guillen-Angel 2024, *Current Opinion in Genetics & Development*, Aug 2024, https://doi.org/10.1016/j.gde.2024.102210 | Mechanistic review; review |
| Mechanism/structure | Human PUS3 forms a homodimer and uses a dimeric scaffold to bind tRNAs; the 2025 review describes an anti-parallel coiled-coil C-terminal helix and interaction with the tRNA elbow plus anticodon stem-loop, explaining why full tRNA architecture is needed for catalysis. Disease variants can impair protein stability without abolishing catalytic chemistry per se. (pqac-00000023, pqac-00000003, pqac-00000004) | I299T formed soluble aggregates, preventing standard biophysical characterization; Y71C preserved binding/activity in vitro but lowered Tm by ~11.3 °C versus WT. (pqac-00000018, pqac-00000003) | Lin 2022, *Human Mutation*, Oct 2022, https://doi.org/10.1002/humu.24471; Lin 2025, *RNA Biology*, 2025, https://doi.org/10.1080/15476286.2025.2541421 | Biochemical; structural/mechanistic review |
| Localization | Available cited sources most consistently place PUS3 in the nucleus and cytoplasm, in line with action on nuclear pre-tRNA/maturing tRNA and cytoplasmic tRNA pools; no evidence in the retrieved sources supports mitochondrial localization. Localization evidence in the retrieved corpus is stronger in reviews than in the 2022 primary biochemical paper. (pqac-00000021, pqac-00000014) | Qualitative only: nucleus + cytoplasm; no mitochondrial localization stated in the cited sources. (pqac-00000021) | Yang 2025, *Cells*, Sep 2025, https://doi.org/10.3390/cells14171380 | Review |
| Cellular roles/pathways | PUS3 functions in the tRNA modification/biogenesis pathway and, by modifying U38/U39 in anticodon loops, influences translation-related outputs. Yeast evidence summarized in review shows reduced stop-codon readthrough and reduced frameshift efficiency when PUS3-dependent Ψ38/39 is absent, implicating anticodon-loop pseudouridylation in decoding behavior and translation fidelity; genetic interaction with La/PUS4 suggests a role in tRNA maturation robustness. (pqac-00000024, pqac-00000015) | Yeast functional effects summarized qualitatively: loss of Ψ38/39 reduced stop-codon readthrough; Ψ39 was required for +1 frameshifts at slippery sequences. (pqac-00000024) | Rintala-Dempsey 2017, *RNA Biology*, Feb 2017, https://doi.org/10.1080/15476286.2016.1276150 | Review synthesizing yeast genetics/translation phenotypes |
| Human disease | Biallelic PUS3 variants cause a rare neurodevelopmental disorder characterized mainly by intellectual disability/developmental delay, epilepsy, hypotonia, microcephaly, and nonspecific dysmorphism. Lin 2022 provides a molecular explanation: patient variants lower cellular PUS3 abundance and reduce PUS3-dependent Ψ39 in fibroblasts; Y71C mainly destabilizes protein, whereas I299T promotes aggregation. (pqac-00000008, pqac-00000003, pqac-00000004) | Cohort of 21 affected individuals from 15 families; epilepsy 13/18 (72%), brain MRI abnormalities 11/15 (73%), microcephaly/anencephaly 13/18 (72%), facial dysmorphism 17/18 (94%), short stature ≤3rd percentile in 8 individuals; 17 distinct variants identified. p.Tyr71Cys gnomAD exome frequency reported as 0.0001 in Europeans. (pqac-00000008, pqac-00000004) | Nøstvik 2021, *Clinical Genetics*, Aug 2021, https://doi.org/10.1111/cge.14051; Lin 2022, *Human Mutation*, Oct 2022, https://doi.org/10.1002/humu.24471 | Clinical genetics; patient-cell functional follow-up |
| Disease/therapeutic context | Recent review literature places PUS3 among human pseudouridine synthases whose dysregulation is relevant to disease biology, listing reported substrates as tRNA and mRNA and linking PUS3 mutations to neurodevelopmental disease. The review emphasizes broader therapeutic interest in RNA pseudouridylation pathways, though direct PUS3-targeted therapies are not established. (pqac-00000009, pqac-00000016) | Qualitative only in cited review; no PUS3-specific therapeutic trial data identified. (pqac-00000016) | Guillen-Angel 2024, *Current Opinion in Genetics & Development*, Aug 2024, https://doi.org/10.1016/j.gde.2024.102210 | Review |
| Database disease association | Open Targets independently supports human disease linkage, showing curated/literature-backed associations between PUS3 and intellectual disability and microcephaly. This database-level convergence is consistent with OMIM/clinical-genetics literature but should be treated as supporting rather than mechanistic evidence. (pqac-00000000) | Open Targets evidence size: 5 for intellectual disability and 5 for microcephaly; association scores ~0.373 and ~0.371, respectively. Literature cited in evidence includes PMIDs 27055666, 30308082, 30697592. (pqac-00000000) | Open Targets Platform search result for PUS3, accessed via tool context; context includes linked literature evidence. (pqac-00000000) | Database |
| Evidence synthesis / annotation confidence | The strongest evidence supports a primary annotation of human PUS3 as a nucleus/cytoplasm-associated TruA-family tRNA pseudouridine synthase for anticodon-loop U38/U39, with disease caused by loss of stable functional enzyme and reduction of cellular Ψ39. Claims for broad human mRNA targeting are less secure than older reviews suggested, because the more recent mechanistic synthesis reports no PUS3-dependent mRNA sites by Pseudo-seq in depleted human cells. (pqac-00000017, pqac-00000023, pqac-00000025) | Confidence is highest for tRNA Ψ38/39 catalysis and neurodevelopmental disease association; lower for direct human mRNA targeting due to conflicting review-era vs newer Pseudo-seq evidence. (pqac-00000023, pqac-00000025) | Lin 2025, *RNA Biology*, 2025, https://doi.org/10.1080/15476286.2025.2541421; Guillen-Angel 2024, *Current Opinion in Genetics & Development*, Aug 2024, https://doi.org/10.1016/j.gde.2024.102210; Lin 2022, *Human Mutation*, Oct 2022, https://doi.org/10.1002/humu.24471 | Integrated assessment from primary + review + database evidence |


*Table: This table summarizes the strongest functional annotation evidence for human PUS3/Q9BZE2 across biochemistry, mechanism, localization, pathway context, and human disease. It is useful for quickly separating high-confidence claims (tRNA Ψ38/39 catalysis, neurodevelopmental disorder association) from less-settled points such as direct human mRNA targeting.*