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.
Schilling
M M
MM
Department of Molecular Physiology and Biophysics, Vanderbilt University Medical School, 8415 MRB IV, 2213 Garland Ave, Nashville, TN 37232-0615, USA.
Oeser
J K
JK
Chandy
J K
JK
Flemming
B P
BP
Allen
S R
SR
O'Brien
R M
RM
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