The human hexokinase II gene promoter: functional characterization and detection of variants among patients with...

Hexokinase II (HKII) plays an important role in facilitating glucose uptake by skeletal muscle, heart, and adipose tissue in response to insulin. We have cloned and sequenced the proximal promoter region of the human HKII gene, determined the transcription start sites and screened the 2.0 kb of the proximal 5' flanking region for variants in non-insulin-dependent diabetic patients and control subjects. We found three variants in this region, one in the 5' untranslated region (G-->C at +217) and two in the promoter region (T-->G at -1043 and G-->A at -1159). The allele frequencies of these variants did not differ between the diabetic and control subjects and these variants are not associated with insulin resistance. Various segments of the human HKII promoter were tested for driving expression of the luciferase reporter gene. The proximal 500 bp and 400 bp of the promoter were sufficient to drive maximal activity in adipocyte (3T3F442A) and myocyte (C2C12F3) cell lines, respectively. This region of the promoter is GC-rich and contains eight consensus binding sites for the transcription factor Sp-1, five for AP-2, two putative response elements for each of insulin and cyclic AMP. The proximal 175 bases of the promoter retained only 7-15% of maximal activity. Sequence elements located between positions -304 and -215 accounted for approximately 80% of the basal HKII promoter. In addition, the region between -215 and -184 contains a negative regulatory element for expression in 3T3F442A but not in C2C12F3 cells.