Abstract
Glucose-6-phosphate dehydrogenase (G6PD) activity differs among tissues and, in liver, with the dietary state of the mouse. Tissue-specific differences in G6PD activity in adipose tissue, liver, kidney, and heart were associated with similar differences in the amount of G6PD mRNA. Regulation of mRNA amount by dietary fat was only observed in liver. In mice fed a low-fat diet, the relative amounts of G6PD mRNA were 3:1:1:0.38, respectively, in the four tissues. Further, the amount of precursor mRNA for G6PD in liver, kidney, and heart reflected the amount of mature mRNA in these tissues, suggesting differing transcriptional activity. Our S1 nuclease and primer-extension analyses indicated that the same transcriptional start site is used in liver, kidney, and adipose tissue, resulting in a common 5′ end of the mRNA in these tissues. Thus, differential regulation is not attributable to alternate promoter usage. A DNase hypersensitivity analysis of the 5′ end of the G6PD gene identified three hypersensitive sites (HS): HS 1 and HS 2 were present in all tissues, whereas HS 3 was liver specific. Thus, regulation of G6PD expression involves both dietary and tissue-specific signals that appear to act via different mechanisms.
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