CH25H

Existing Annotations Review

GO Term	Evidence	Action	Reason
GO:0005789 endoplasmic reticulum membrane	IBA GO_REF:0000033	ACCEPT	Summary: Correct core localization. CH25H is an ER-membrane multi-pass integral membrane protein; UniProt reports ER membrane localization and three transmembrane helices. The phylogenetic (IBA) inference agrees with experimental/ISS localization. Supporting Evidence: file:human/CH25H/CH25H-uniprot.txt CC -!- SUBCELLULAR LOCATION: Endoplasmic reticulum membrane CC {ECO:0000250\|UniProtKB:Q9Z0F5}; Multi-pass membrane protein CC {ECO:0000250\|UniProtKB:Q9Z0F5}.
GO:0001567 cholesterol 25-hydroxylase activity	IBA GO_REF:0000033	ACCEPT	Summary: This is the core molecular function of CH25H. The phylogenetic inference matches the experimentally demonstrated cholesterol 25-hydroxylase activity (EC 1.14.99.38). Supporting Evidence: file:human/CH25H/CH25H-uniprot.txt Catalyzes the formation of 25-hydroxycholesterol from
GO:0036197 zymosterol biosynthetic process	IBA GO_REF:0000033	REMOVE	Summary: Incorrect IBA propagation. The PAINT IBD for zymosterol biosynthesis sits on PTN002275159 (Eumetazoa) and is seeded only by mouse Msmo1, a C-4 methylsterol oxidase of the post-lanosterol cholesterol pathway (PANTHER subfamily SF225). CH25H lies in a separate subfamily (PTHR11863:SF213, CHOLESTEROL 25-HYDROXYLASE) whose own PAINT node (PTN002627316) carries only cholesterol 25-hydroxylase activity. CH25H acts on the finished cholesterol molecule, downstream of zymosterol, and no study places it in the C-4 demethylation steps that produce zymosterol. Reason: Full re-review (2026-10-20). The source node grants a pathway role defined by C-4 methylsterol oxidation chemistry that the CH25H subfamily diverged from; the CH25H-specific node deliberately carries a different activity. Because the term is wrong for this gene product, not merely broad, REMOVE replaces the earlier MARK_AS_OVER_ANNOTATED. Propagation Review Root cause: PROPAGATION BAD Failure modes: FUNCTIONAL DIVERGENCE Sources checked: PANTHER:PTN002275159 · sterol desaturase family node SUPPORTS SOURCE BUT NOT TARGET Family node for methylsterol/zymosterol-processing members; CH25H diverged to C-25 hydroxylation of cholesterol. MGI:MGI:1913484 · Msmo1 (mouse) SUPPORTS SOURCE BUT NOT TARGET Methylsterol oxidase acting in zymosterol biosynthesis; not the substrate/role of CH25H. Supporting Evidence: file:human/CH25H/CH25H-uniprot.txt Catalyzes the formation of 25-hydroxycholesterol from
GO:0000254 C-4 methylsterol oxidase activity	IBA GO_REF:0000033	REMOVE	Summary: Incorrect IBA propagation. The IBD sits on the deep eukaryote node PTN000221246 of PTHR11863, seeded by C-4 methylsterol oxidases (human MSMO1, yeast ERG25, plant SMO1/SMO2 genes). CH25H belongs to a separate subfamily (PTHR11863:SF213) whose PAINT node PTN002627316 carries cholesterol 25-hydroxylase activity, seeded by mouse Ch25h and human CH25H. The demonstrated CH25H reaction is side-chain C-25 hydroxylation of cholesterol, which has no C-4 methyl group to oxidise, and no study reports C-4 methylsterol oxidase activity for CH25H. Reason: Full re-review (2026-10-20). Shared histidine-box diiron chemistry makes the family a sterol oxygenase family, but substrate and position specificity diverged among subfamilies. The PTHR11863 family review (interpro/panther/PTHR11863/PTHR11863-review.yaml) reaches the same conclusion, that C-4 methylsterol oxidase activity is not a family-wide grant and is not supported for CH25H. The term is wrong for this gene, so REMOVE replaces the earlier MARK_AS_OVER_ANNOTATED. Propagation Review Root cause: PROPAGATION BAD Failure modes: FUNCTIONAL DIVERGENCE Sources checked: UniProtKB:Q15800 · MSMO1 (human) SUPPORTS SOURCE BUT NOT TARGET Bona fide C-4 methylsterol oxidase; CH25H shares the fatty-acid-hydroxylase/histidine-box fold but hydroxylates cholesterol at C-25. SGD:S000003292 · ERG25 (yeast) SUPPORTS SOURCE BUT NOT TARGET C-4 methylsterol oxidase of ergosterol biosynthesis; family-level activity that did not transfer to CH25H's true function. PANTHER:PTN000221246 · sterol desaturase family node SUPPORTS SOURCE BUT NOT TARGET Broad family node; C-4 methylsterol oxidase activity is over-general for CH25H. Supporting Evidence: PMID:9852097 Here, we report the cloning of cholesterol
GO:0001567 cholesterol 25-hydroxylase activity	IEA GO_REF:0000120	ACCEPT	Summary: Correct core molecular function, redundant with the experimental annotations to the same term. The automated IEA (via ortholog Q9Z0F5, RHEA, and EC:1.14.99.38) agrees with experiment. Supporting Evidence: file:human/CH25H/CH25H-uniprot.txt Catalyzes the formation of 25-hydroxycholesterol from
GO:0005506 iron ion binding	IEA GO_REF:0000002	ACCEPT	Summary: Biologically correct and consistent with the enzyme mechanism. CH25H is a diiron enzyme (not a heme/P450); UniProt records an Fe cation cofactor and the conserved histidine-box motifs coordinate the diiron center. Iron ion binding is part of the catalytic machinery. Supporting Evidence: PMID:9852097 it is a member of a small family of enzymes that utilize diiron
GO:0005789 endoplasmic reticulum membrane	IEA GO_REF:0000044	ACCEPT	Summary: Correct core localization, derived from the UniProt subcellular-location mapping. Consistent with the experimental/ISS and IBA ER-membrane annotations. Supporting Evidence: file:human/CH25H/CH25H-uniprot.txt CC -!- SUBCELLULAR LOCATION: Endoplasmic reticulum membrane CC {ECO:0000250\|UniProtKB:Q9Z0F5}; Multi-pass membrane protein CC {ECO:0000250\|UniProtKB:Q9Z0F5}.
GO:0008610 lipid biosynthetic process	IEA GO_REF:0000002	KEEP AS NON CORE	Summary: Correct InterPro2GO annotation. CH25H synthesizes the oxysterol 25-hydroxycholesterol, a lipid, so it does perform a step of lipid biosynthesis. GO has no oxysterol or 25-hydroxycholesterol biosynthetic process term (checked by label search of GO), and the specific process the gene carries, cholesterol metabolic process, is not a descendant of lipid biosynthetic process, so no refinement is available. Reason: As precise as the ontology allows for the product side of the reaction; peripheral to the core description, which is expressed through the MF and cholesterol metabolic process. Supporting Evidence: PMID:9852097 cholesterol 25-hydroxylases, polytopic membrane proteins that synthesize a potent oxysterol regulator of lipid metabolism
GO:0005515 protein binding	IPI PMID:32296183 A reference map of the human binary protein interactome.	REMOVE	Summary: Bare protein binding from the HuRI systematic yeast two-hybrid interactome, here with OTX1 (P32242), a nuclear homeobox transcription factor. No functional relationship to an ER-membrane cholesterol hydroxylase is known, and the term carries no information about CH25H function. Reason: Per the repository protein-binding policy, a bare GO:0005515 row is removed as uninformative; removal does not assert that the reported interaction is false. No more informative MF is supported by the screen.
GO:0035754 B cell chemotaxis	IEA GO_REF:0000107	KEEP AS NON CORE	Summary: Downstream/indirect physiological role transferred from the mouse ortholog. CH25H does not itself have chemotactic activity; its product 25-HC is converted to 7alpha,25-dihydroxycholesterol, a GPR183/EBI2 ligand that guides B-cell positioning. Biologically reasonable but indirect and non-core. Supporting Evidence: PMID:33239446 25HC is further converted to 7-α, 25-dihydroxycholesterol (7-α, 25-diHC), an oxysterol that functions as a chemoattractant for T cells and B cells
GO:0090206 negative regulation of cholesterol metabolic process	IEA GO_REF:0000107	KEEP AS NON CORE	Summary: Captures the well-established regulatory role of 25-HC as an SREBP co-repressor that suppresses cholesterol biosynthesis. Transferred electronically from the mouse ortholog but supported by human experimental work showing reduced cholesterol synthesis and blocked SREBP processing. Regulatory and downstream of the catalytic MF, so kept as non-core. Supporting Evidence: PMID:9852097 the biosynthesis of cholesterol from acetate and suppresses the cleavage of
GO:0001567 cholesterol 25-hydroxylase activity	EXP PMID:33239446 Cholesterol 25-hydroxylase suppresses SARS-CoV-2 replication...	ACCEPT	Summary: Core molecular function, directly demonstrated. The catalytic His-His double mutant abolished 25-HC production, confirming CH25H is the enzyme producing 25-HC from cholesterol. Supporting Evidence: PMID:33239446 mutant CH25H did not produce 25HC and 7-α, 25-diHC
GO:0001567 cholesterol 25-hydroxylase activity	EXP PMID:9852097 cDNA cloning of mouse and human cholesterol 25-hydroxylases,...	ACCEPT	Summary: Core molecular function, from the original cloning and catalytic characterization of human and mouse cholesterol 25-hydroxylases. Establishes the diiron, non-P450 nature of the enzyme. Supporting Evidence: PMID:9852097 Here, we report the cloning of cholesterol
GO:0005789 endoplasmic reticulum membrane	ISS GO_REF:0000024	ACCEPT	Summary: Correct core localization, inferred by sequence similarity from the mouse ortholog (Q9Z0F5). Consistent with the multi-pass membrane topology and the IBA/IEA ER-membrane annotations. Supporting Evidence: file:human/CH25H/CH25H-uniprot.txt CC -!- SUBCELLULAR LOCATION: Endoplasmic reticulum membrane CC {ECO:0000250\|UniProtKB:Q9Z0F5}; Multi-pass membrane protein CC {ECO:0000250\|UniProtKB:Q9Z0F5}.
GO:0001567 cholesterol 25-hydroxylase activity	IDA PMID:32944968 Cholesterol 25-Hydroxylase inhibits SARS-CoV-2 and other cor...	ACCEPT	Summary: Core molecular function, directly assayed. CH25H converts cholesterol to 25-hydroxycholesterol; this study demonstrates production of 25-HC and its antiviral consequences in human cells. Supporting Evidence: PMID:32944968 CH25H converts cholesterol to 25-hydrocholesterol (25HC)
GO:0008203 cholesterol metabolic process	IDA PMID:33239446 Cholesterol 25-hydroxylase suppresses SARS-CoV-2 replication...	ACCEPT	Summary: Correct core biological process: CH25H catalyzes a step of cholesterol/oxysterol metabolism, converting cholesterol to 25-HC. Directly supported by the demonstrated catalytic activity. Supporting Evidence: PMID:33239446 CH25H encodes cholesterol 25-hydroxylase that catalyzes the formation of 25-hydroxycholesterol (25HC) from cholesterol
GO:0034340 response to type I interferon	IDA PMID:33239446 Cholesterol 25-hydroxylase suppresses SARS-CoV-2 replication...	KEEP AS NON CORE	Summary: CH25H is an interferon-stimulated gene, induced by type I interferon and acting as one of the antiviral effectors of that response through its product 25-HC. The annotation is supported, but it records the cellular context in which the enzyme is deployed rather than what the enzyme does. Reason: Full re-review (2026-10-20). Changed from ACCEPT to KEEP_AS_NON_CORE; the core function is the C-25 hydroxylation, and the antiviral consequence is captured more precisely by GO:1903914. Supporting Evidence: PMID:33239446 Cholesterol 25-hydroxylase (CH25H) is an interferon (IFN)-stimulated gene that
GO:1903914 negative regulation of fusion of virus membrane with host plasma membrane	IDA PMID:32944968 Cholesterol 25-Hydroxylase inhibits SARS-CoV-2 and other cor...	ACCEPT	Summary: Well-supported antiviral biological process. CH25H/25-HC blocks coronavirus spike-mediated membrane fusion by activating ER ACAT and depleting accessible plasma-membrane cholesterol. Supporting Evidence: PMID:32944968 These results strongly support a function for 25HC in blocking human coronavirus spike
GO:1903914 negative regulation of fusion of virus membrane with host plasma membrane	IDA PMID:33239446 Cholesterol 25-hydroxylase suppresses SARS-CoV-2 replication...	ACCEPT	Summary: Well-supported antiviral biological process (independent confirmation). CH25H expression and 25-HC block SARS-CoV-2 spike-mediated membrane fusion; the catalytic mutant, which cannot make 25-HC, loses antiviral activity, tying the phenotype to the enzyme's product. Supporting Evidence: PMID:33239446 our data support a model that 25HC suppresses SARS-CoV-2 S protein-mediated fusion, which inhibits virus replication
GO:0001567 cholesterol 25-hydroxylase activity	ISS GO_REF:0000024	ACCEPT	Summary: Core molecular function, inferred by sequence similarity from mouse (Q9Z0F5) and redundant with the direct experimental annotations to the same term. Consistent. Supporting Evidence: file:human/CH25H/CH25H-uniprot.txt Catalyzes the formation of 25-hydroxycholesterol from
GO:0035754 B cell chemotaxis	ISS GO_REF:0000024	KEEP AS NON CORE	Summary: Downstream/indirect physiological role inferred by similarity from mouse. Same as the Ensembl IEA to this term: CH25H does not have chemotactic activity itself; its product feeds 7alpha,25-diHC/EBI2-mediated lymphocyte positioning. Non-core. Supporting Evidence: PMID:33239446 25HC is further converted to 7-α, 25-dihydroxycholesterol (7-α, 25-diHC), an oxysterol that functions as a chemoattractant for T cells and B cells
GO:0005829 cytosol	TAS Reactome:R-HSA-191983	REMOVE	Summary: Mislocalization. This TAS annotation reflects the compartment assigned to a Reactome reaction ("Cholesterol is hydroxylated to 25-hydroxycholesterol"), not the location of the enzyme. CH25H is a polytopic integral membrane protein of the ER (three predicted transmembrane helices, N-glycosylated); it is not a soluble cytosolic protein. The ER membrane annotations are the accurate ones. Reason: Full re-review (2026-10-20). An integral ER-membrane enzyme is not located in the cytosol; a reaction-compartment artifact is a demonstrably wrong localization, so REMOVE replaces the earlier MARK_AS_OVER_ANNOTATED. Supporting Evidence: file:human/CH25H/CH25H-uniprot.txt CC -!- SUBCELLULAR LOCATION: Endoplasmic reticulum membrane CC {ECO:0000250\|UniProtKB:Q9Z0F5}; Multi-pass membrane protein CC {ECO:0000250\|UniProtKB:Q9Z0F5}.
GO:0006629 lipid metabolic process	TAS PMID:9852097 cDNA cloning of mouse and human cholesterol 25-hydroxylases,...	MODIFY	Summary: Correct but very general. CH25H converts cholesterol to 25-hydroxycholesterol, a step of cholesterol metabolism; GO:0008203 cholesterol metabolic process is a descendant of lipid metabolic process and is already carried by this gene (IDA, PMID:33239446). Reason: Full re-review (2026-10-20). Per the refinement rule, a correct but general term is MODIFY to the specific supported descendant rather than KEEP_AS_NON_CORE. Proposed replacements: cholesterol metabolic process Supporting Evidence: PMID:9852097 a potent oxysterol regulator of lipid metabolism
GO:0008395 steroid hydroxylase activity	TAS PMID:9852097 cDNA cloning of mouse and human cholesterol 25-hydroxylases,...	MODIFY	Summary: Correct but overly general: this is the direct parent of GO:0001567 cholesterol 25-hydroxylase activity, which is the specific, experimentally demonstrated activity. Recommend replacing with the specific child term. Proposed replacements: cholesterol 25-hydroxylase activity Supporting Evidence: PMID:9852097 Here, we report the cloning of cholesterol
GO:0005515 protein binding	IPI PMID:32296183 A reference map of the human binary protein interactome.	REMOVE	Summary: Bare protein binding from the HuRI systematic yeast two-hybrid interactome, here with KRTAP12-4 (P60329), a hair keratin-associated protein. No functional relationship to an ER-membrane cholesterol hydroxylase is known, and the term carries no information about CH25H function. Reason: Per the repository protein-binding policy, a bare GO:0005515 row is removed as uninformative; removal does not assert that the reported interaction is false. Made consistent with the sibling OTX1 row from the same screen (previously the two rows carried different actions).

Gene Description

Existing Annotations Review

Core Functions

Cholesterol 25-hydroxylase: an ER-membrane, diiron (non-P450) oxygenase that hydroxylates cholesterol at C-25 to produce the regulatory oxysterol 25-hydroxycholesterol, using molecular oxygen and iron.

Iron cofactor binding for catalysis: CH25H coordinates a diiron center (conserved histidine-box motifs) required for its monooxygenase activity.

Antiviral effector function of the 25-HC product: as an interferon-stimulated gene, CH25H restrains enveloped-virus infection by blocking virus membrane fusion with the host plasma membrane.

References

Deep Research

Falcon

Manual

📚 Additional Documentation

Notes

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