Sterol regulatory element binding proteins(SREBPs) are membrane-bound transcription factors that activate genes encoding enzymes of cholesterol and fatty acid biosynthesis.SREBPs are synthesized as precursor proteins in the endoplasmic reticulum(ER),where they form a complex with another protein,SREBP cleavage activating protein(SCAP).SCAP escorts SREBP to activation in the Golgi apparatus.There,SREBP undergoes two proteolytic cleavage steps to release the mature,biologically active transcription factor,nuclear SREBP(nSREBP).The process is induced by two proteins,SCAP and Insig.This review is to summarize the role of SCAP and Insig in the procession and maturation of SREBP and the lipid metabolism.