FIG. 9.

Stabilization of SREBP1a affects cholesterol metabolism. (A) 293T cells were transfected with the vector alone (−) or Flag-tagged wild-type SREBP1a (WT) or K333Q (MUT). Thirty-six hours after transfection, total RNA was extracted and used to determine the expression of the LDLR and HMG-CoA reductase genes by quantitative real-time PCR. The results are presented as the factors by which mRNA levels increased relative to the mRNA levels found in cells transfected with the vector alone. The results represent the averages ± standard deviations of one representative experiment performed in triplicate. (B) 293T cells were transfected with either the vector alone (−) or Flag-tagged wild-type SREBP1a or K333Q (MUT). Thirty-six hours after transfection, cells were placed in fresh media supplemented with [¹⁴C]acetate. Nonpolar lipids were extracted and resolved by thin-layer chromatography (TLC). Radioactive products were visualized after exposure of the TLC plates to X-ray film.