Search

Carbohydrate response element-binding protein (ChREBP) is a glucose-dependent transcription factor that stimulates the expression of glycolytic and lipogenic genes in mammals. Glucose regulation of ChREBP has been mapped to its conserved NHz-terminal region of 300 amino acids, designated the MondoA conserved region (MCR). Within the MCR, five domains (MCR1-5) have a particularly high level of conservation and are likely to be important for glucose regulation. We carded out a large-scale deletion and substitution mutational analysis of the MCR domain of ChREBP. This analysis revealed that MCRs 1-4 function in a concerted fashion to repress ChREBP activity in basal (nonstimulatory) conditions. Deletion of the entire MCR1-4 segment or the combination of four specific point mutations located across this region leads to a highly active, glucose-independent form of ChREBP. However, deletion of any individual MCR domain and the majority of point mutations throughout MCR1-4 rendered ChREBP inactive. These observations suggest that the MCR1-4 region interacts with an additional coregulatory factor required for activation. This possibility is supported by the observation that the MCR1-4 region can compete for activity with wild-type ChREBP in stimulatory conditions. In contrast, mutations in the MCR5 domain result in increased activity, suggesting that this domain may be the target of intramolecular repression in basal conditions. Thus, the MCR domains act in a complex and coordinated manner to regulate ChREBP activity in response to glucose. carbohydrate response element-binding protein; transcription; lipogenesis; glucose signaling doi: 10.1152/ajpendo.00349.2010.

Armstrong, Michael B., and Howard C. Towle. Polyunsaturated fatty acids stimulate hepatic UCP-2 expression via a PPAR.-mediated pathway. Am J Physiol Endocrinol Metab 281: E 1197-E 1204, 2001.--The discovery of homologs of the brown fat uncoupling protein(s) (UCP) UCP-2 and UCP-3 revived the hypothesis of uncoupling protein involvement in the regulation of energy metabolism. Thus we hypothesized that UCP-2 would be regulated in the hepatocyte by fatty acids, which are known to control other energy-related metabolic processes. Treatment with 250 [micro] M palmitic acid was without effect on UCP-2 expression, whereas 250 [micro] M oleic acid exhibited a modest eightfold increase. Eicosapentaenoic acid (EPA), a polyunsaturated fatty acid, exerted a 50-fold upregulation of UCP-2 that was concentration dependent. This effect was seen within 12 h and was maximal by 36 h. Aspirin blocked the induction of UCP-2 by EPA, indicating involvement of the prostaglandin pathway. Hepatocytes treated with arachidonic acid, the immediate precursor to the prostaglandins, also exhibited an aspirin-inhibitable increase in UCP-2 levels, further supporting the involvement of prostaglandins in regulating hepatic UCP-2. The peroxisome proliferator-activated receptor-[alpha] (PPAR[alpha]) agonist Wy-14643 stimulated UCP-2 mRNA levels as effectively as EPA. These data indicate that UCP-2 is upregulated by polyunsaturated fatty acids, potentially through a prostaglandin/PPAR[alpha]-mediated pathway. uncoupling protein; prostaglandins; energy metabolism; peroxisome proliferator-activated receptor-[alpha] Received 7 February 2001; accepted in final form 31 July 2001

The proximal promoters of the genes examined focusing on signal transducer and activation of transcription (STAT) binding sites contained in these promoter elements to investigate the role of STAT proteins in the divergent regulation of the Spi 2.1 and Spi 2.2 genes after induction of acute phase response. Differential regulation of Spi 2.1 and 2.2 genes is partly caused by differences in the promoters of these genes at the gamma-activated sequence sites. Interleukin-6 alone fails to reproduce the pattern of rat Spi 2 gene expression that results from turpentine-induced inflammation.

Chronic exposure of HIT-T15 [beta] cells to elevated glucose concentrations leads to decreased insulin gene transcription. The reduction in expression is accompanied by diminished binding of a glucose-sensitive transcription factor (termed GSTF) that interacts with two (A+T)-rich elements within the 5' flanking control region of the insulin gene. In this study we examined whether GSTF corresponds to the recently cloned insulin gene transcription factor STF-1, a homeodomain protein whose expression is restricted to the nucleus of endodermal cells of the duodenum and pancreas. We found that an affinity-purified antibody recognizing STF-1 supershifted the GSTF activator complex formed from HIT-T15 extracts. In addition, we demonstrated a reduction in STF-1 mRNA and protein levels that closely correlated with the change in GSTF binding in HIT-T15 cells chronically cultured under supraphysiologic glucose concentrations. The reduction in STF-1 expression in these cells could be accounted for by a change in the rate of STF-1 gene transcription, suggesting a posttranscriptional control mechanism. In support of this hypothesis, no STF-1 mRNA accumulated in HIT-T15 cells passaged in 11.1 mM glucose. The only RNA species detected was a 6.4-kb STF-1 RNA species that hybridized with 5' and 3' STF-1-specific cDNA probes. We suggest that the 6.4-kb RNA represents an STF-1 mRNA precursor and that splicing of this RNA is defective in these cells. Overall, this study suggests that reduced expression of a key transcriptional regulatory factor, STF-1, contributes to the decrease in insulin gene transcription in HIT-T15 cells chronically cultured in supraphysiologic glucose concentration.

Human embryonic nervous system is damaged by the congenital deficiency of iodine, a thyroid hormone component, resulting in sensori-neural deafness. The human beta thyroid hormone receptor gene causes this iodine deficiency in children. The prominent expression of the gene results in permanent deafness by restricting the development of the cochlea.