Upstream Activation Sequence

Inositol-sensitive upstream activation sequence (UAS_INO)

The inositol-sensitive upstream activation sequence (UAS_INO) has a consensus sequence 5'-CATGTGAAAT-3' and is present in the promoter regions of genes that encode enzymes of phospholipid biosynthesis. These enzymes are regulated by inositol and choline, both of which are phospholipid precursors. Within this consensus sequence, the first six bases are homologous with canonical binding motif for proteins within the bHLH or the basic helix-loop-helix family. Studies have shown that Ino2p and Ino4p, two bHLH regulatory proteins from Saccharomyces cerevisiae, bind to promoter fragments containing this element of the consensus sequence. Additional studies have been designed to explore the function of UAS_INO in more detail largely in part because a large number of phospholipid biosynthetic enzyme activities in the model organism Saccharomyces cerevisiae show this common pattern of expression.