Differential Regulatory Response for the Δ9 Desaturase in Saccharomyces cerevisiae Based on Fatty Acid Species and Membrane-Altering Conditions

Unsaturated fatty acids (UFAs) regulate the expression of OLE1, the gene encoding the Δ9 desaturase in the yeast Saccharomyces cerevisiae. Previous work has demonstrated that the transcription factors Mga2p and Spt23p are required for OLE1 expression, and that differential processing controls their activity. We have examined how the structure of unsaturated fatty acids and environmental conditions affect the processing of Mga2 and Spt23p and control the regulation of OLE1. We have found that yeast grown in UFAs 16:1Δ9, and 18:2Δ9,12 strongly repress transcription of OLE1, while 18:1Δ9 and 17:1Δ10 had a lesser effect in a wild-type strain. We also examined how these exogenous UFAs control the processing of Mga2p and Spt23p in wild-type yeast. We have found that cells grown in 17:1Δ10, and 18:2Δ9,12 have all of the Spt23p protein in inactive form, while the other growth conditions Mga2p and Spt23p can be found in both the active and the inactive form