Genetic screen to identify regulators of nuclear sterol regulatory element binding protein (SREBP) in fission yeast

Abstract

Sterol regulatory element binding proteins (SREBPs) are membrane‐bound transcription factors that control lipid homeostasis in mammalian cells. Sterols regulate the activation of SREBP by inhibiting ER‐Golgi transport of SREBP and proteolysis in the Golgi. While much is known about the mechanisms of sterol‐dependent ER retention, less is known about regulation of the nuclear form of SREBP. To identify novel regulators of nuclear SREBP, we designed a genetic selection scheme in Schizosaccharomyces pombe that reports the in vivo activity of nuclear Sre1, the fission yeast ortholog of SREBP. This selection uses a yeast strain containing a ura4+ reporter gene driven by multiple Sre1 DNA binding elements. This scheme allowed us to perform a growth‐dependent, plasmid‐based, high copy suppressor screen for regulators of nuclear Sre1. To date, we have identified both positive and negative candidate regulators of nuclear Sre1, including 2 kinases. This genetic screen should give us a broader view of Sre1 regulation in yeast and identify candidate regulators of SREBP in mammalian cells. Research was funded by a grant from the NIH HL‐077588 and a Burroughs Wellcome Fund Career Award in the Biomedical Sciences (PJE).