... Rbx1, and one of afamily of F-box proteins, Fbw7 [17]. Glycogen syn-thase kinase-3b phosphorylates serine and ⁄ or threonineresidues near the ubiquitination site in SREBP-1 and SREBP-2, and ... their specific ligands are present, HNF-4 and LRH-1 appear to be exceptional, in that they are con-stitutively active in the abundance of their endogenousligands, acyl-CoA and phospholipids, ... themature forms of SREBPs, which enter the nucleus and activate genes related to cholesterol and fattyacid metabolism [1,2]. In both the cytoplasm and nucleus, SREBPs associate with a variety of...