SAS4
S. cerevisiae
Sas4p
What the model saw
Gene: SAS4 Organism: Saccharomyces cerevisiae Known functions: Sas4p. acetyltransferase activity. histone acetyltransferase activity. protein binding.
View unredacted entry
Sas4p. acetyltransferase activity. histone acetyltransferase activity. protein binding.
Solver output
SAS4 encodes a component of the SAS (Something About Silencing) histone acetyltransferase complex in S. cerevisiae, which is responsible for acetylating histone H4 at lysine 16 (H4K16ac) and lysine 12 (H4K12ac). H4K16 acetylation is a critical epigenetic mark that regulates chromatin structure and transcriptional silencing at telomeres and the HM loci; its proper maintenance is tightly linked to replicative lifespan in yeast. Loss of H4K16ac at subtelomeric regions is a hallmark of aging in yeast, and the SAS complex counteracts the deacetylase Sir2 to maintain appropriate acetylation balance. By sustaining H4K16ac levels, SAS4 helps preserve proper chromatin architecture and gene expression patterns, opposing the epigenetic drift associated with aging. Thus, the normal acetyltransferase function of SAS4 is expected to support longevity by maintaining epigenetic homeostasis.
GenAge curators classify each gene's normal function as promoting (Pro-Longevity) or opposing (Anti-Longevity) longevity, based on synthesis across studies. Loss-of-function effects can vary from this depending on the manipulation.
Advisor judgment
The model predicted pro_longevity but the ground truth is anti_longevity. The model's reasoning about SAS4's role in H4K16 acetylation and the SAS complex is partially correct in terms of biochemical function, but the conclusion about longevity is wrong. In yeast, SAS4 (part of the SAS-I complex) acetylates H4K16, which actually antagonizes silencing at telomeres and HM loci by competing with Sir2-mediated deacetylation. Loss of silencing at these loci is associated with aging, but the SAS complex's role in promoting H4K16ac can actually reduce silencing and thus be anti-longevity. The model incorrectly reasoned that maintaining H4K16ac supports longevity, when in fact SAS4 activity (by opposing Sir2-mediated silencing) is anti-longevity. The model had moderate confidence (0.62) but reached the wrong conclusion with flawed mechanistic reasoning about the direction of the effect.
Raw API responses
solver
{
"reasoning": "SAS4 encodes a component of the SAS (Something About Silencing) histone acetyltransferase complex in S. cerevisiae, which is responsible for acetylating histone H4 at lysine 16 (H4K16ac) and lysine 12 (H4K12ac). H4K16 acetylation is a critical epigenetic mark that regulates chromatin structure and transcriptional silencing at telomeres and the HM loci; its proper maintenance is tightly linked to replicative lifespan in yeast. Loss of H4K16ac at subtelomeric regions is a hallmark of aging in yeast, and the SAS complex counteracts the deacetylase Sir2 to maintain appropriate acetylation balance. By sustaining H4K16ac levels, SAS4 helps preserve proper chromatin architecture and gene expression patterns, opposing the epigenetic drift associated with aging. Thus, the normal acetyltransferase function of SAS4 is expected to support longevity by maintaining epigenetic homeostasis.",
"confidence": 0.62,
"key_pathways": [
"H4K16 acetylation / SAS complex",
"telomeric silencing and chromatin regulation",
"Sir2-SAS acetyltransferase balance"
],
"mechanism_class": "epigenetic_alterations",
"longevity_influence": "pro_longevity"
}advisor
{
"notes": "The model predicted pro_longevity but the ground truth is anti_longevity. The model's reasoning about SAS4's role in H4K16 acetylation and the SAS complex is partially correct in terms of biochemical function, but the conclusion about longevity is wrong. In yeast, SAS4 (part of the SAS-I complex) acetylates H4K16, which actually antagonizes silencing at telomeres and HM loci by competing with Sir2-mediated deacetylation. Loss of silencing at these loci is associated with aging, but the SAS complex's role in promoting H4K16ac can actually reduce silencing and thus be anti-longevity. The model incorrectly reasoned that maintaining H4K16ac supports longevity, when in fact SAS4 activity (by opposing Sir2-mediated silencing) is anti-longevity. The model had moderate confidence (0.62) but reached the wrong conclusion with flawed mechanistic reasoning about the direction of the effect.",
"failure_mode": "confident_wrong",
"answer_correct": false,
"mechanism_correct": false,
"reasoning_quality": 2,
"ground_truth_questionable": false
}