Sequence variation between the mouse and human glucose-6-phosphatase catalytic subunit gene promoters results in differential activation by peroxisome proliferator activated receptor gamma coactivator-1alpha.
OBJECTIVE
The glucose-6-phosphatase catalytic subunit (G6PC) plays a key role in hepatic glucose production by catalysing the final step in gluconeogenesis and glycogenolysis. Peroxisome proliferator activated receptor gamma coactivator-1alpha (PGC-1alpha) stimulates mouse G6pc-luciferase fusion gene expression through hepatocyte nuclear factor-4alpha (HNF-4alpha), which binds an element located between -76 and -64 in the promoter. The aim of this study was to compare the regulation of mouse G6pc and human G6PC gene expression by PGC-1alpha.


METHODS
PGC-1alpha action was analysed by transient transfection and gel retardation assays.


RESULTS
In H4IIE cells, PGC-1alpha alone failed to stimulate human G6PC-luciferase fusion gene expression even though the sequence of the -76 to -64 HNF-4alpha binding site is perfectly conserved in the human promoter. This difference could be explained, in part, by a 3 bp sequence variation between the mouse and human promoters. Introducing the human sequence into the mouse G6pc promoter reduced PGC-1alpha-stimulated fusion gene expression, whereas the inverse experiment, in which the mouse sequence was introduced into the human G6PC promoter, resulted in the generation of a G6PC-luciferase fusion gene that was now induced by PGC-1alpha. This critical 3 bp region is located immediately adjacent to a consensus nuclear hormone receptor half-site that is perfectly conserved between the mouse G6pc and human G6PC promoters. Gel retardation experiments revealed that this 3 bp region influences the affinity of HNF-4alpha binding to the half-site.


CONCLUSIONS
These observations suggest that PGC-1alpha may be more important in the control of mouse G6pc than human G6PC gene expression.
Department of Molecular Physiology and Biophysics, Vanderbilt University Medical School, 8415 MRB IV, 2213 Garland Ave, Nashville, TN 37232-0615, USA.
M M
MM
Schilling
J K
JK
Oeser
J K
JK
Chandy
B P
BP
Flemming
S R
SR
Allen
R M
RM
O'Brien
D000818:Animals; D001483:Base Sequence; D017124:Conserved Sequence; D004789:Enzyme Activation; D017930:Genes, Reporter; D014644:Genetic Variation; D005952:Glucose-6-Phosphatase / Q000235:genetics* / Q000378:metabolism; D006360:Heat-Shock Proteins / Q000378:metabolism*; D006801:Humans; D008156:Luciferases / Q000235:genetics; D051379:Mice; D008969:Molecular Sequence Data; D000071248:Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha; D010957:Plasmids; D011401:Promoter Regions, Genetic; D021122:Protein Subunits / Q000235:genetics; D016415:Sequence Alignment; D015534:Trans-Activators / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism*; D014162:Transfection
D006360:Heat-Shock Proteins; C486497:PPARGC1A protein, human; D000071248:Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha; C485290:Ppargc1a protein, mouse; D021122:Protein Subunits; D015534:Trans-Activators; D014157:Transcription Factors; D008156:Luciferases; D005952:Glucose-6-Phosphatase