AARSD1 encodes a conserved AlaX-family trans-editing factor that functions in the cytoplasm to hydrolyze mischarged aminoacyl-tRNAs and preserve translational fidelity. The literature and UniProt support AARSD1 as a proofreading enzyme rather than an alanine-tRNA ligase. Recent direct work on human AlaX shows broad activity against Ser-mischarged tRNAs and links AARSD1 loss to Ala- and Thr-to-Ser mistranslation, supporting a translation-quality-control role as core biology. A proposed HSP90 cochaperone interpretation is not supported as a core gene-level assignment for canonical AARSD1; the relevant muscle-differentiation paper appears to map to non-canonical readthrough-derived PTGES3L-AARSD1 fusion isoforms noted by UniProt for isoforms 2 and 3. That HSP90-related role is best treated as contextual and isoform-associated rather than a general function of canonical AARSD1.
Curated functional classes representing distinct biological activities. These may be splice variants, cleavage products, or other forms with different functions.
AARSD1_ALAXAARSD1_READTHROUGH_FUSION| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0002196 Ser-tRNA(Ala) deacylase activity | IBA GO_REF:0000033 | ACCEPT | Summary: This phylogenetically inferred annotation matches the now directly supported core activity of human AARSD1/AlaX. Human AlaX is a Ser-selective trans-editing factor, and Ser-tRNA(Ala) deacylation remains the defining conserved function of the AlaX family. Reason: Appropriate core molecular-function annotation for canonical AARSD1. Supporting Evidence: PMID:38869066 human AlaX (hAlaX), which is exclusively distributed in the cytoplasm, is an active trans-editing factor with strict Ser-specificity file:human/AARSD1/AARSD1-uniprot.txt Functions in trans to edit the amino acid moiety from incorrectly charged tRNA(Ala). |
| GO:0006450 regulation of translational fidelity | IBA GO_REF:0000033 | ACCEPT | Summary: AARSD1 clearly participates in translational fidelity control by proofreading mischarged tRNAs. The term is broader than the mechanistic process term GO:0106074, but it remains biologically true. Reason: Supported parent-level process annotation for the gene's proofreading role. Supporting Evidence: PMID:38869066 loss of ScAlaX or hAlaX readily induced Ala- and Thr-to-Ser misincorporation PMID:38869066 provide multiple checkpoints to maintain the speed and fidelity of genetic decoding file:human/AARSD1/AARSD1-deep-research-falcon.md AARSD1/hAlaX is positioned in a translation quality-control pathway that prevents (or reduces) amino acid misincorporation |
| GO:0106074 aminoacyl-tRNA metabolism involved in translational fidelity | IEA GO_REF:0000120 | ACCEPT | Summary: This is the most mechanistically informative biological-process term among the existing translation-quality-control annotations. AARSD1 removes incorrect amino acids from charged tRNAs after aminoacylation, matching the term definition. Reason: Directly supported by recent human AlaX work and consistent with UniProt curation. Supporting Evidence: PMID:38869066 In vitro, both hAlaX and yeast AlaX (ScAlaX) were capable of hydrolyzing nearly all Ser-mischarged cytoplasmic and mitochondrial tRNAs PMID:38869066 provide multiple checkpoints to maintain the speed and fidelity of genetic decoding file:human/AARSD1/AARSD1-deep-research-falcon.md hydrolyzes mischarged aa-tRNAs (especially serine-mischarged tRNAs) to protect proteome fidelity and modulate decoding dynamics |
| GO:0002161 aminoacyl-tRNA deacylase activity | IEA GO_REF:0000120 | ACCEPT | Summary: The generic deacylase term is appropriate because human AlaX has broader activity than only Ser-tRNA(Ala) hydrolysis and acts on multiple Ser-mischarged tRNA species in the 2024 human study. Reason: Supported core molecular function and a good summary term for the expanded substrate range of eukaryotic AlaX. Supporting Evidence: PMID:38869066 active trans-editing factor with strict Ser-specificity PMID:38869066 hydrolyzing nearly all Ser-mischarged cytoplasmic and mitochondrial tRNAs file:human/AARSD1/AARSD1-deep-research-falcon.md The best-supported primary biochemical function of human AARSD1 is deacylation (hydrolysis) of misacylated aa-tRNAs |
| GO:0002196 Ser-tRNA(Ala) deacylase activity | IEA GO_REF:0000107 | ACCEPT | Summary: The orthology-transferred annotation is consistent with both the conserved AlaX family assignment and direct human evidence. Reason: Correct orthology-supported annotation for canonical AARSD1. Supporting Evidence: PMID:38869066 active trans-editing factor with strict Ser-specificity file:human/AARSD1/AARSD1-uniprot.txt Functions in trans to edit the amino acid moiety from incorrectly charged tRNA(Ala). |
| GO:0000166 nucleotide binding | IEA GO_REF:0000002 | REMOVE | Summary: This InterPro-derived annotation appears to conflate AARSD1 with catalytic alanine-tRNA synthetases. The canonical human protein is an AlaX editing factor rather than a nucleotide-dependent ligase, and current curated sources emphasize proofreading plus zinc binding rather than nucleotide binding. Reason: No convincing evidence for a standalone nucleotide-binding function of canonical AARSD1. Supporting Evidence: PMID:38869066 active trans-editing factor with strict Ser-specificity file:human/AARSD1/AARSD1-uniprot.txt Functions in trans to edit the amino acid moiety from incorrectly charged tRNA(Ala). |
| GO:0003676 nucleic acid binding | IEA GO_REF:0000002 | MARK AS OVER ANNOTATED | Summary: AARSD1 necessarily contacts tRNA substrates, but this generic term is far less informative than the specific deacylase activities already present. The annotation adds little biological value and blurs the actual proofreading function. Reason: Substrate binding is implicit in the catalytic proofreading activity; generic nucleic acid binding is too broad for this gene. Supporting Evidence: PMID:38869066 hydrolyzing nearly all Ser-mischarged cytoplasmic and mitochondrial tRNAs |
| GO:0004812 aminoacyl-tRNA ligase activity | IEA GO_REF:0000002 | REMOVE | Summary: This is a domain/family-based overcall from the gene name and remote synthetase homology. Canonical AARSD1 lacks the core aminoacylation role of AARS1 and is instead an editing enzyme that acts in trans after aminoacylation. Reason: Incorrect molecular-function assignment for canonical AARSD1. Supporting Evidence: PMID:38869066 The trans-editing factor AlaX predominantly hydrolyzes Ser-tRNAAla file:human/AARSD1/AARSD1-uniprot.txt Functions in trans to edit the amino acid moiety from incorrectly charged tRNA(Ala). |
| GO:0004813 alanine-tRNA ligase activity | IEA GO_REF:0000002 | REMOVE | Summary: This is even more specifically incorrect than GO:0004812. The alanine-charging enzyme is AARS1, whereas AARSD1 is the trans-editing AlaX factor that proofreads mischarged tRNAs. Reason: Not supported for canonical AARSD1; this annotation conflates editing with aminoacylation. Supporting Evidence: PMID:38869066 The trans-editing factor AlaX predominantly hydrolyzes Ser-tRNAAla file:human/AARSD1/AARSD1-uniprot.txt Functions in trans to edit the amino acid moiety from incorrectly charged tRNA(Ala). |
| GO:0005524 ATP binding | IEA GO_REF:0000002 | REMOVE | Summary: ATP binding is inferred here from the same mistaken synthetase-like propagation that produced the ligase annotations. Neither UniProt nor the direct human AlaX study supports ATP-dependent aminoacylation as a function of canonical AARSD1. Reason: Likely a false positive carried over from aaRS homology rather than an authentic activity of AARSD1. Supporting Evidence: PMID:38869066 active trans-editing factor with strict Ser-specificity file:human/AARSD1/AARSD1-uniprot.txt Name=Zn(2+) |
| GO:0005737 cytoplasm | IEA GO_REF:0000044 | ACCEPT | Summary: Cytoplasmic localization is strongly supported and fits the proofreading role of canonical AARSD1 in cytoplasmic translation quality control. Reason: Best-supported core localization for the canonical protein. Supporting Evidence: PMID:38869066 human AlaX (hAlaX), which is exclusively distributed in the cytoplasm file:human/AARSD1/AARSD1-uniprot.txt SUBCELLULAR LOCATION: Cytoplasm |
| GO:0006419 alanyl-tRNA aminoacylation | IEA GO_REF:0000002 | REMOVE | Summary: This annotation incorrectly assigns the aminoacylation step itself to AARSD1. The protein functions downstream as a proofreading factor and does not charge tRNA with alanine. Reason: AARSD1 maintains fidelity after aminoacylation rather than catalyzing alanine charging. Supporting Evidence: PMID:38869066 The trans-editing factor AlaX predominantly hydrolyzes Ser-tRNAAla PMID:32484512 while wrong amino acids are corrected within an aaRS, a wrong tRNA is handled in trans by an aaRS cognate to the mischarged tRNA species |
| GO:0043039 tRNA aminoacylation | IEA GO_REF:0000002 | REMOVE | Summary: As with the alanine-specific process term above, this broader aminoacylation annotation conflates proofreading with the charging reaction itself. Reason: Canonical AARSD1 is a trans-editing factor, not an aminoacyl-tRNA synthetase. Supporting Evidence: PMID:38869066 The trans-editing factor AlaX predominantly hydrolyzes Ser-tRNAAla |
| GO:0005634 nucleus | HDA PMID:21630459 Proteomic characterization of the human sperm nucleus. | KEEP AS NON CORE | Summary: The evidence is a high-throughput proteomic characterization of purified human sperm nuclei, not a focused localization study of canonical AARSD1 in typical somatic cells. This makes the nuclear call plausible as a specialized context but not part of the core localization/function profile of the gene. Reason: Keep as a context-specific observation only; the canonical and directly tested localization remains cytoplasmic. Supporting Evidence: PMID:21630459 403 different proteins have been identified from the isolated sperm nuclei PMID:38869066 human AlaX (hAlaX), which is exclusively distributed in the cytoplasm |
| GO:0003674 molecular_function | ND GO_REF:0000015 | REMOVE | Summary: This placeholder annotation reflected the absence of curated function at an earlier stage and is now obsolete. Reason: AARSD1 has directly supported proofreading activities and no longer requires an ND placeholder. |
| GO:0008150 biological_process | ND GO_REF:0000015 | REMOVE | Summary: This placeholder annotation is obsolete because AARSD1 now has well-supported biological-process assignments tied to translational fidelity. Reason: Replace generic ND with the supported translation-quality-control terms above. |
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Download this section (compressed HTML)Q: Does human muscle primarily express the canonical AARSD1 proofreading isoform, PTGES3L-AARSD1 readthrough fusion proteins, or both under differentiation conditions?
Q: Is the sperm-nuclear detection of AARSD1 a true specialized localization or a context-dependent carryover from highly abundant translation-quality-control machinery?
Q: Which endogenous mischarged human tRNA species dominate AARSD1 dependence in vivo outside the cell systems tested in PMID:38869066?
Experiment: Isoform-specific long-read RNA-seq plus targeted proteomics in human skeletal muscle and differentiating myoblasts to distinguish canonical AARSD1 from PTGES3L-AARSD1 readthrough products.
Hypothesis: The reported HSP90-cochaperone activity maps to readthrough-derived fusion isoforms rather than to canonical AARSD1.
Type: transcriptomics/proteomics
Experiment: CRISPR knockout or degron depletion of canonical AARSD1 followed by mistranslation proteomics to quantify Ala- and Thr-to-Ser substitutions in human cells.
Hypothesis: Loss of canonical AARSD1 increases specific serine misincorporation events predicted from AlaX proofreading defects.
Type: genetic manipulation/proteomics
Experiment: Endogenous isoform-resolved localization of canonical AARSD1 and readthrough-derived fusion proteins in sperm and somatic cells using isoform-specific tagging or proteotypic peptides.
Hypothesis: Canonical AARSD1 is predominantly cytoplasmic, whereas any nuclear or HSP90-associated signal is restricted to specialized contexts or readthrough-derived isoforms.
Type: microscopy/proteomics
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