Characterization of the mevalonate kinase 5′-untranslated region provides evidence for coordinate regulation of cholesterol biosynthesis

Using a probe derived from the 5'-untranslated region of the human mevalonate kinase (MK) cDNA, we screened a lambda gt 11 genomic library and obtained a single clone containing the 5' untranslated region of the gene, Nucleotide sequencing identified several putative regulatory elements, including two Sp1 (GC box) elements and a CCAAT box, A canonical TATA box was not detected, Directly adjacent to one Spl element was a sterol regulatory element (SRE), 5'-CACCCCAG-3', which was a 7/8 base pair match to the consensus sequences identified in the genes encoding 3-hydroxy-3-methylglutaryl-coenzyme A synthase and reductase, and the LDL receptor, There was no Spl element upstream of the SRE. Northern blot analysis in human CRL1508T cells revealed that quantities of MK poly A(+) RNA increased for cells grown in the presence of lipid-deficient calf serum, and further increased upon addition of 1 mu M lovastatin, Primer extension analysis with human poly A(+) RNA suggested at least 4 transcription initiation sites downstream from the CCAAT box, To assess sterol responsiveness of transcription initiation, a 1.4 kb genomic fragment upstream of the translational start site was fused to the pSV2(cat) vector for transient expression in COS-7 cells, with chloramphenicol acetyltransferase (CAT) as the reporter gene, This construct demonstrated modest levels of CAT expression which was induced > 2-fold when cells were grown in Lipoprotein-deficient calf serum, Our data provide further evidence for coordinate regulation of cholesterol biosynthesis in response to sterol, (C) 1998 Academic Press.