FunctionTranscriptional activator required for lipid homeostasis. Regulates transcription of the LDL receptor gene as well as the cholesterol and to a lesser degree the fatty acid synthesis pathway (By similarity). Binds the sterol regulatory element 1 (SRE-1) (5'-ATCACCCCAC-3') found in the flanking region of the LDRL and HMG-CoA synthase genes.
Tissue specificityUbiquitously expressed in adult and fetal tissues.
Sequence similaritiesBelongs to the SREBP family. Contains 1 basic helix-loop-helix (bHLH) domain.
Post-translational modificationsAt low cholesterol the SCAP/SREBP complex is recruited into COPII vesicles for export from the ER. In the Golgi complex SREBPs are cleaved sequentially by site-1 and site-2 protease. The first cleavage by site-1 protease occurs within the luminal loop, the second cleavage by site-2 protease occurs within the first transmembrane domain and releases the transcription factor from the Golgi membrane. Apoptosis triggers cleavage by the cysteine proteases caspase-3 and caspase-7.
Cellular localizationNucleus and Endoplasmic reticulum membrane. Golgi apparatus membrane. Cytoplasmic vesicle > COPII-coated vesicle membrane. Moves from the endoplasmic reticulum to the Golgi in the absence of sterols.