In an earlier study [Choi, Lundquist and Peffley (1993) Biochem. J. 296, 859-866], we determined that 25-hydroxycholesterol regulates 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) reductase mRNA through a post-transcriptional mechanism that requires protein synthesis. To investigate whether 3'-untranslated sequences play a role in 25-hydroxycholesterol-mediated post-transcriptional control, we ligat...