ERG28 (ergosterol biosynthesis 28 homolog) is a non-catalytic, membrane-associated protein localized to the endoplasmic reticulum that functions as a scaffold in sterol biosynthesis 1. The protein is conserved from yeast to humans and plays a critical role in cholesterol synthesis, particularly in C-4 demethylation of sterol intermediates 2. ERG28 interacts with catalytic enzymes NSDHL and SC4MOL, and likely tethers multiple demethylation proteins (Erg25p, Erg26p, Erg27p) into a functional complex 13. Transcription of ERG28 is regulated by SREBP-2, the master transcription factor controlling cholesterol synthesis genes 3. ERG28 knockout studies in mammalian cells demonstrate 60-75% reduction in cholesterol synthesis rates and decreased total cholesterol levels in sterol-depleted conditions, with effects partially mediated through impaired SREBP-2 activation 3. Beyond classical sterol synthesis, ERG28 is a unique target gene for intestinal PXR nuclear receptor activation 4. Clinically, ERG28 emerges as a potential biomarker correlating with prostate cancer immunotherapy response and favorable outcome in rectal cancer treated with neoadjuvant chemoradiotherapy 56. The gene is highly expressed in testis and cancer cell lines 7, suggesting potential roles beyond sterol metabolism.