Alternative products:Additional isoforms seem to exist ,Function:Transcriptional activator required for lipid homeostasis. Regulates transcription of the LDL receptor gene as well as the fatty acid and to a lesser degree the cholesterol synthesis pathway (By similarity) . Binds to the sterol regulatory element 1 (SRE-1) (5'-ATCACCCCAC-3') . Has dual sequence specificity binding to both an E-box motif (5'-ATCACGTGA-3') and to SRE-1 (5'-ATCACCCCAC-3') . ,online information:Sterol regulatory element-binding protein entry ,PTM:At 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. ,sequence Caution:Intron retention. ,similarity:Belongs to the SREBP family. ,similarity:Contains 1 basic helix-loop-helix (bHLH) domain. ,subcellular location:Moves from the endoplasmic reticulum to the Golgi in the absence of sterols. ,subunit:Forms a tight complex with SCAP in the ER membrane. Efficient DNA binding of the soluble transcription factor fragment requires dimerization with another bHLH protein. Interacts with LMNA. ,tissue specificity:Expressed in a wide variety of tissues , most abundant in liver and adrenal gland. In fetal tissues lung and liver shows highest expression. Isoform SREBP-1C predominates in liver , adrenal gland and ovary , whereas isoform SREBP-1A predominates in hepatoma cell lines. Isoform SREBP-1A and isoform SREBP-1C are found in kidney , brain , white fat , and muscle. ,
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