A novel gene conserved from yeast to humans is involved in sterol biosynthesis

The ERG28 gene was originally identified by microarray expression profiling as possibly involved in the Saa charomyces cerevisiae sterol pathway, Micr oarray analyses suggested that the transcription pattern of ERG28 closely f ollowed that of genes involved in sterol synthesis, ERG28 was also found in Schizosaccharomyces pombe and Arabidopsis as well as humans, and in the la tter was shown to be highly expressed in adult testis tissue. All four prot eins contain potential transmembrane domain(s), Gas chromatography-mass spe ctrometry analysis of an ERG28-deleted S, cerevisiae strain (which is slow growing but not auxotrophic for ergosterol) indicates a lesion in sterol C- 4 demethylation, Sterol:profiles indicate accumulation of 3-keto and carbox ylic acid sterol intermediates, which are involved in removing the two C-4 methyl groups from the sterol A ring. Similar intermediates have previously been demonstrated to accumulate in erg26 (sterol dehydrogenase/decarboxyla se) and erg27 (3-ketoreductase) mutants in yeast, We speculate that the rol e of the Erg28 protein (Erg28p) may be either to tether Erg26p and Erg27p t o the endoplasmic reticulum or to facilitate interaction between these prot eins.