Studies on the transcriptional regulation of genes involved in fatty acid and cholesterol metabolism by SREBP

SREBP是一种转录因子，在调节脂肪酸和胆固醇代谢相关酶和蛋白质的基因中起着关键作用，HMG CoA合成酶和角鲨烯合成酶基因的启动子都含有多个SREBP和NF-Y结合位点。使用在SREBP结合位点和NF-Y结合位点之间含有各种核苷酸间隔长度的构建体的报道基因测定证明16 - 20-bp的间隔范围是最大转录调节所需的，为了研究SREBP家族的两个成员SREBP-1和SREBP-2在各自生理功能上的差异，我们利用lac-switch系统建立了瞬时表达SREBP-2的HeLa细胞系，当细胞与甾醇类化合物共同培养时，SREBP-2优先刺激与胆固醇代谢相关的基因的转录，而不刺激与脂肪酸代谢相关的基因的转录，说明SREBP-2主要调控胆固醇代谢，而SREBP-1主要调控脂肪酸代谢。

SREBP is a transcription factor which plays a critical role in regulation of genes encoding enzymes and proteins involved in fatty acid and cholesterol metabolism.The promoters of both HMG CoA synthase and squalene synthase genes contain multiple SREBP-binding and NF-Y-binding sites.A number of reporter luciferase assays revealed that SREBP and NF-Y, a ubiquitous transcription factor, coordinately regulate transcription of these genes.Reporter gene assays using constructs containing various nucleotide spacing lengths between the SREBP-binding and NF-Y-binding sites demonstrate that the 16 to 20-bp spacing range is required for maximal transcriptional regulation, suggesting that the interaction between them might be critical for the coordinate regulation.To investigate the difference between two members of SREBP family, SREBP-l and -2, in the individual physiological roles, a HeLa cell line transiently expressing SREBP-2 was established using a lac-switch system.When the cell was cultured with sterols, endogenous SREBPs were inactivated and exogenous SREBP-2 was transiently active.SREBP-2 preferentially stimulate the transcription of genes related to cholesterol metabolism, not to fatty acid metabolism.These results indicate that SREBP-2 mainly regulates cholesterol metabolism while SREBP-l regulates fatty acid metabolism.