ERG2

Summary: Core C-8 sterol isomerase activity propagated from the fungal ERG2 PAINT node.

Reason: PTN001280219 is the fungal ERG2 PAINT node seeded by Candida and S. cerevisiae ERG2 activity evidence, and it is separate from the animal Sigma-receptor nodes in PTHR10868. The propagated activity matches the enzymatic step assigned to C. albicans ERG2 by UniProt/Rhea and the direct CGD experimental rows.

Summary: CGD inferred C-8 sterol isomerase activity for the C. albicans erg2 mutant from S. cerevisiae ERG2.

Reason: The cached Pierson et al. paper is abstract-only, but the abstract confirms that the study used a C. albicans erg2 ergosterol-biosynthetic mutant. Because the full text was available to CGD curators and the same activity is supported by the fungal PAINT node, UniProt's S. cerevisiae transfer, and the expected fecosterol-to-episterol reaction, this direct Candida experimental row should be retained.

Summary: CGD IMP evidence for C-8 sterol isomerase activity from the C. albicans erg2 mutant is consistent with all ERG2 family evidence.

Reason: Pierson et al. directly studied a C. albicans erg2 ergosterol mutant. The cached abstract does not expose the full mutant characterization, so the review defers to CGD full-text curation; the assigned molecular function is the conserved ERG2 reaction and is also supported by the PAINT and ISS transfers.

Summary: Manual sequence-similarity transfer from S. cerevisiae ERG2 correctly captures the conserved fungal sterol C-8 isomerase activity.

Reason: C. albicans ERG2 and S. cerevisiae ERG2 fall in the same fungal PTHR10868:SF1 ERG2/SigmaR subfamily, and C-8 sterol isomerization is the core late ergosterol-biosynthetic reaction of fungal ERG2 proteins. This ISS transfer is consistent with the more recent fungal PAINT placement.

Summary: Root cellular component ND annotation: when it was made, no cellular component had been curated for this gene product from literature.

Reason: ACCEPT under the ND acceptance rule (projects/NO_DATA.md). The evidence this review cites for the cellular component is inferred (from orthologs, family membership or sequence features) or comes from other species; none of it is literature on this gene product in this species. This was judged from the review's own content during the NO_DATA re-action pass, not from a new literature search. Earlier action: KEEP_AS_NON_CORE.

Summary: PTHR10868 ER localization transfer from the broad ERG2/SIGMAR1-family node is valid for C. albicans ERG2.

Reason: The source node PTN001328958 is broad, with fungal ERG2 and animal SIGMAR1 descendants, but the ER compartment is shared and biologically appropriate for the C. albicans sterol C-8 isomerase. The animal-specific Sigma-receptor signaling and postsynaptic rows are confined to different PTN descendants and were not transferred to this fungal target.

Summary: UniProt subcellular-location transfer places C. albicans ERG2 at the ER membrane.

Reason: ERG2 acts in the late sterol-biosynthetic pathway with other ER-associated sterol enzymes and is predicted by UniProt to be a single-pass ER-membrane protein. This is the most specific current compartment row for the C. albicans enzyme.

Summary: Fungal ERG2 PAINT transfer correctly assigns the ergosterol biosynthetic process.

Reason: The PTHR10868 node carrying this term is the fungal ERG2 node seeded by PomBase and SGD ERG2 entries, and the C. albicans protein catalyzes the fecosterol-to-episterol step in the UniPathway/Rhea late ergosterol route. ERG2 therefore performs one of the pathway reactions itself.

Summary: UniPathway transfer to sterol biosynthesis is a true parent of the ergosterol-specific pathway assignment.

Reason: The UniPathway mapping is broader than the fungal PAINT ergosterol row, but it is not misleading: ergosterol biosynthesis is a fungal sterol biosynthetic pathway and ERG2 directly catalyzes the reaction from fecosterol to episterol.

Summary: ERG2 chemical-genetic response phenotypes are real but secondary to the core sterol-isomerase step.

Reason: Xu et al. used the CaFT heterozygous deletion pool to profile responses to inhibitory compounds and reports the additional ergosterol-biosynthesis inhibitor profiles in supplemental Text S1, Figure S2, and Table S1. The cached main text does not expose the ERG2-specific supplementary result, so this review defers to CGD for the row. The response phenotype is biologically plausible because ERG2 mutants alter membrane sterol composition and show altered susceptibility to multiple xenobiotics, but it is a downstream phenotype rather than the gene's core catalytic role.