Vanadate inhibits expression of the gene for phosphoenolpyruvate carboxykinase (GTP) in rat hepatoma cells
Bosch i Tubert, Fàtima (Universitat Autònoma de Barcelona. Departament de Bioquímica i de Biologia Molecular)
Hatzoglou, Maria (Case Western Reserve University School of Medicine (Cleveland, Estats Units d'Amèrica))
Park, Edwards A. (Case Western Reserve University School of Medicine (Cleveland, Estats Units d'Amèrica))
Hanson, Richard W. (Case Western Reserve University School of Medicine (Cleveland, Estats Units d'Amèrica))

Data:	1990
Resum:	Vanadate, at concentrations between 0. 5 and 2 mM, rapidly decreased the basal level of P-enolpyruvate carboxykinase (GTP) (EC 4. 1. 1. 32) mRNA and blocked the dibutyryl cyclic AMP (Bt2CAMP)-induced increase in enzyme mRNA in both FTO-2B and H4IIE rat hepatoma cells. The concentration of vanadate necessary to inhibit the expression of this gene was similar to that required for the vanadate-mediated activation of the insulin receptor tyrosine kinase. To determine whether vanadate could inhibit PEPCK gene transcription, a series of chimeric genes containing several deletions in the P-enolpyruvate carboxykinase promoter between -550 and -68 was linked to the structural genes for either amino-3-glycosyl phosphotransferase (neo) or chloramphenicol acetyltransferase and introduced into hepatoma cells using three methods: (a) infection with a Moloney murine leukemia virus-based retrovirus, (b) transfection and stable selection for neo expression, or (c) transient expression of chloramphenicol acetyltransferase. In FTO-2B hepatoma cells infected with retrovirus, vanadate rapidly (within 1 h) inhibited transcription of the PEPCK-neo gene and blocked induction of gene expression caused by the addition of either Bt2CAMP or dexamethasone to the cells. Vanadate was not a general transcription inhibitor since, it like insulin, stimulated the expression of the c-fos gene. Also, the inhibitory effect of vanadate was rapidly reversible in FTO-2B cells since PEPCK gene expression could be stimulated by Bt2CAMP and dexamethasone after removal of vanadate. A series of 5' deletions in the P-enolpyruvate carboxykinase promoter (-550 to +73) was ligated to the structural gene for neo and stably transfected into hepatoma cells. Sequences responsive to vanadate were detected between -109 and -68. This result was confirmed using H4IIE hepatoma cells transiently expressing the PEPCK-CAT gene. The most likely target for vanadate in that region of the P-enolpyruvate carboxykinase promoter is cAMP regulatory element 1 which maps from -91 to -84. A comparison of the inhibitory effects of insulin and vanadate in this system indicated a major difference in the site of action of these two compounds on PEPCK gene transcription.
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Llengua:	Anglès
Document:	Article ; recerca ; Versió publicada
Publicat a:	Journal of biological chemistry, Vol. 265 Núm. 23 (1990) , p. 13677-13682, ISSN 1083-351X

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