SPAC25B8.09

Summary: Genome-wide YFP-fusion localization of the target protein observed nuclear signal.

Reason: Direct high-throughput observation on the target protein, recorded by PomBase and reflected with experimental attribution in the UniProt record. The ORFeome paper is abstract-only in the cache, but the curated observation is target-specific and there is no conflicting evidence. Nuclear plus cytosolic signal is typical of a small soluble enzyme that can diffuse through nuclear pores.

Summary: SubCell mapping of the experimentally attributed UniProt nucleus location.

Reason: Electronic mapping of the UniProt subcellular-location line, which itself rests on the target HDA observation (PMID:16823372). Consistent with the accepted HDA row for the same term.

Summary: Correct but general; the underlying observation is cytosolic.

Reason: The UniProt "Cytoplasm" location derives from the same localization study that PomBase curated more precisely as cytosol (HDA, PMID:16823372). The protein has no transmembrane segment, signal peptide or organelle-targeting annotation, so the specific supported term is cytosol (GO:0005829), which the gene already carries.

Proposed replacements: cytosol

Summary: Genome-wide YFP-fusion localization of the target protein observed cytosolic signal.

Reason: Direct target observation curated by PomBase; consistent with a soluble small-molecule methyltransferase (budding-yeast Tmt1 activity is also cytosolic). The cached paper is abstract-only, so the curator judgment is deferred to.

Summary: Correct; the PAINT node is deep and the more specific SAM-dependent term is supported.

Reason: PTN008676703 is a deep class I methyltransferase node whose donors span several PANTHER families (E. coli RlmA, human TMT1A/METTL7A, M. tuberculosis Rv2952, P. aeruginosa PA4379); the curator propagated only the generic methyltransferase term, and did not use Tmt1 as a donor or propagate any acceptor-specific activity, which is read here as a deliberate decision. The methyl-transfer claim is sound. The gene also carries the more specific SAM-dependent methyltransferase activity (GO:0008757), supported by the Methyltransf_11 domain and SAM-dependent MTase superfamily signatures, so that term is the better statement of the same claim.

Proposed replacements: S-adenosylmethionine-dependent methyltransferase activity

Summary: SAM-dependent methyltransferase activity is the best-supported molecular function.

Reason: The Methyltransf_11 domain (IPR013216/PF08241) and SAM-dependent MTase superfamily membership define the catalytic class, and the PTHR44942:SF4 subfamily contains experimentally active SAM-dependent carboxyl methyltransferases (budding-yeast Tmt1). This is as specific as the evidence allows; the methyl acceptor is unknown.

Summary: Transferred from Tmt1, where the link to amino acid starvation is Gcn4-driven induction and a budding-yeast-specific invasive-growth signal.

Reason: In budding yeast, Tmt1 is transcriptionally induced by amino acid starvation via Gcn4, and its product 3-isopropylmalate methyl ester was proposed to signal haploid invasive growth. Induction is an expression response rather than evidence that the enzyme executes the starvation response, and the invasive-growth signalling is a Saccharomyces-specific physiology. For SPAC25B8.09, one-to-one orthology to TMT1 is not resolved (the two fission-yeast SF4 paralogs are about equidistant from Tmt1 and Crg1), so a donor-specific process cannot be transferred with confidence. No fission-yeast data link this gene to the starvation response.

Summary: Plausible but not established; the acceptor specificity of this SF4 member is unresolved.

Reason: Tmt1 trans-aconitate methyltransferase activity is experimentally established, and SPAC25B8.09 shares PTHR44942:SF4 with it. However the substrate-specific claim requires orthology, and the evolutionary placement does not resolve it - fission yeast has a lineage-specific tandem pair (SPAC25B8.09/SPAC25B8.10, 68% identical), budding yeast has Tmt1 and Crg1, and each fission-yeast copy is 25-29% identical to both budding-yeast proteins. SF4 also contains natural-product O-methyltransferases with unrelated acceptors, and the official PANTHER 19.0 classification places Q9UTA9 in a different family (PTHR42912:SF95). The PAINT curator propagated only generic methyltransferase activity to this gene. Trans-aconitate methylation remains a reasonable hypothesis, but neither the target nor its paralog has been assayed.

Summary: Detoxification of trans-aconitate is a hypothesis even for the donor, and orthology is unresolved.

Reason: For Tmt1, the detoxification role is an inference from trans-aconitate being an aconitase inhibitor ("appears to be"), and its major endogenous substrate is 3-isopropylmalate, not trans-aconitate. Transferring a speculative physiological process from a donor whose orthology to SPAC25B8.09 is not resolved overstates what is known. Retained as a possible role pending substrate identification.