The Role of Nro1p in Recognition and Signaling the Presence of Dietary Unsaturated Fatty Acids

Abstract

The OLE1 gene in Saccharomyces cerevisiae encodes the sole fatty acyl desaturase in that species. OLE1 gene expression is controlled in part through transcriptional regulators Mga2p and Spt23p. These proteins reside in the ER, and when an insufficient supply of unsaturated fatty acids (UFAs) is detected, they are proteolytically cleaved and translocated into the nucleus, where they activate OLE1 expression. Recently our lab has isolated a mutant that is deficient in regulation of OLE1, called nro1 (no regulation of OLE1). The mechanism for the NRO1 protein's action is unknown. In this study, we report that growth tests using a reporter gene under control of the OLE1 promoter demonstrate that in wild type cells, normal regulation is observed with the UFAs 16:1Δ9 and 18:2Δ9, 12 but not with UFAs 18:1Δ9 or 17:1Δ9. Fatty acid profiles of nro1 mutant cells are similar to wildtype when cells are supplemented with the various UFAs, showing evidence of post‐transciptional regulation. Results examining the effect of nro1 on the proteolytic processing of Mga2p and Spt23p through western analysis are presented. Taken together, there is evidence that the NRO1 system helps to regulate OLE1 expression in response to fatty acids 16:1Δ9 and 18:2Δ9, 12, but not 18:1Δ9 or 17:1Δ9. Supported by a Summer Research Scholar Award from Hope College Biology Department