Protein involved in regulation of sterol biosynthesis; stabilizes Hmg2p, one of two HMG-CoA isoenzymes that catalyze the rate-limiting step in sterol biosynthesis; localizes to the ER; localizes to the nucleus-vacuole junction during glucose restriction; homolog of mammalian INSIG proteins; NSG2 has a paralog, NSG1, that arose from the whole genome duplication