Figure 1.

Reduction of SREBP-1c transcripts after treatment of cultured McA-RH7777 cells with compactin and reversal with LXR-agonist T0901317. On day 0, cells were set up in medium A supplemented with 10% FCS as described in Materials and Methods. On day 2, the cells were washed with PBS and switched to medium B containing 10% delipidated serum with (lanes 4–6 and 10–12) or without (lanes 1–3 and 7–9) 50 μM sodium compactin and 50 μM sodium mevalonate. Certain dishes also received a mixture of cholesterol (10 μg/ml) and increasing concentrations of 25-hydroxycholesterol (25-HC) as indicated. Some of the cells received 10 μM of T0901317. After incubation at 37°C for 16 h, cells were harvested, and 20-μg aliquots of total RNA from pooled dishes were hybridized for 10 min at 68°C to ³²P-labeled cRNA probes for rat SREBP-1, SREBP-2, and β-actin as described in Materials and Methods. After digestion with RNase A/T1, protected fragments were separated by gel electrophoresis and exposed to film for 8 h at −80°C as described in Materials and Methods. The relative levels of the SREBP-1a, -1c, and -2 transcripts in lane 1 were 1.0, 2.9, and 4.6, respectively, as quantified by using a PhosphorImager as described in Materials and Methods.