KLF10 is a modulatory factor of chondrocyte hypertrophy in developing skeleton.

To define the functional role of Krüppel-like factor (KLF) 10 as a modulator of chondrocyte hypertrophy in developing skeleton, the developmental features in the long bone of KLF10 knockout (KO) mice were investigated and the mesenchymal stem cells (MSCs) from KLF10 KO mice were characterized regarding chondrogenesis and osteogenesis. Delayed long bone growth and delayed formation of primary ossification center were observed in an early embryonic stage in KLF10 KO mouse along with very low Indian hedgehog expression in epiphyseal plate. While the chondrogenic potential of mouse MSCs from KLF10 KO mice appeared normal or slight decreased, hypertrophy and osteogenesis were extensively suppressed. These findings suggest that KLF10 is a mediator of chondrocyte hypertrophy in developing skeleton, and that suppression of KLF10 may be employed as a new strategy for preventing hypertrophy in cartilage regeneration using MSCs.

Deletion of KLF10 Leads to Stress-Induced Liver Fibrosis upon High Sucrose Feeding.

Liver fibrosis is a consequence of chronic liver injury associated with chronic viral infection, alcohol abuse, and nonalcoholic fatty liver. The evidence from clinical and animal studies indicates that transforming growth factor-ß (TGF-ß) signaling is associated with the development of liver fibrosis. Krüppel-like factor 10 (KLF10) is a transcription factor that plays a significant role in TGF-ß-mediated cell growth, apoptosis, and differentiation. In recent studies, it has been reported to be associated with glucose homeostasis and insulin resistance. In the present study, we investigated the role of KLF10 in the progression of liver disease upon a high-sucrose diet (HSD) in mice. Wild type (WT) and Klf10 knockout (KO) mice were fed either a control chow diet or HSD (50% sucrose) for eight weeks. Klf10 KO mice exhibited significant hepatic steatosis, inflammation, and liver injury upon HSD feeding, whereas the WT mice exhibited mild hepatic steatosis with no apparent liver injury. The livers of HSD-fed Klf10 KO mice demonstrated significantly increased endoplasmic reticulum stress, oxidative stress, and proinflammatory cytokines. Klf10 deletion led to the development of sucrose-induced hepatocyte cell death both in vivo and in vitro. Moreover, it significantly increased fibrogenic gene expression and collagen accumulation in the liver. Increased liver fibrosis was accompanied by increased phosphorylation and nuclear localization of Smad3. Here, we demonstrate that HSD-fed mice develop a severe liver injury in the absence of KLF10 due to the hyperactivation of the endoplasmic reticulum stress response and CCAAT/enhance-binding protein homologous protein (CHOP)-mediated apoptosis of hepatocytes. The current study suggests that KLF10 plays a protective role against the progression of hepatic steatosis into liver fibrosis in a lipogenic state.

The differential expression of the blood group P1 -A4GALT and P2 -A4GALT alleles is stimulated by the transcription factor early growth response 1.

BACKGROUND: The P1 /P2 phenotypic polymorphism is one of the earliest blood groups discovered in humans. These blood groups have been connected to different levels of expression of the A4GALT gene in P1 and P2 red blood cells; however, the detailed molecular genetic mechanism that leads to these two phenotypes has not been established. STUDY DESIGN AND METHODS: After our previous identification of an association between the single-nucleotide polymorphisms (SNPs) rs2143918 and rs5751348 in A4GALT gene and the P1 /P2 phenotype, we conduct a survey of transcription factors that might connect these SNPs with the differential expression of the P1 -A4GALT and P2 -A4GALT alleles. An in silico analysis of potential transcription factor binding motifs within the polymorphic SNPs rs2143918 and rs5751348 genomic regions was performed, and this was followed by reporter assays examining the candidate transcription factors, gene expression profiling, electrophoretic mobility shift assays, and P1 -A4GALT and P2 -A4GALT allelic expression analysis. RESULTS: The results revealed that the differential binding of transcription factor early growth response 1 to the SNP rs5751348 genomic region with the different genotypes in the A4GALT gene leads to differential activation of P1 -A4GALT and P2 -A4GALT expression. CONCLUSION: The present investigation, together with our previous study (Lai et al., Transfusion 2014;54:3222-31), have elucidated the molecular genetic details associated with the P1 /P2 blood groups.

Krüpple-like factor 10 regulates radio-sensitivity of pancreatic cancer via UV radiation resistance-associated gene.

BACKGROUND AND PURPOSE: Krüpple-like factor 10 (Klf10), an early response gene of TGFß, was reported to be a prognostic biomarker for pancreatic cancer survival. The role of Klf10 in predicting tumor response to cancer treatment is unknown. MATERIALS AND METHODS: Genetically manipulated MiaPaCa and Panc-1 cells were established to evaluate clonogenic survival, autophagy, apoptosis and DNA repair after radiation. The interaction between Klf10 and UV radiation resistance-associated gene (UVRAG) was demonstrated by ChiP-PCR and luciferase reporter assay. Orthotopic murine tumor model and clinical specimens were used to evaluate radio-sensitivity of pancreatic cancer. RESULTS: We found Klf10 silencing correlates with enhanced pancreatic cancer clonogenic survival and murine tumor growth after radiation. UVRAG was an essential down-stream mediator transcriptionally suppressed by Klf10. Silencing UVRAG mRNA in Klf10 depleted Panc-1 cells reversed the radio-resistant phenotypes including decreased apoptosis and enhanced DNA repair as well as autophagy. Metformin, an anti-diabetic agent, was found to increase Klf10 and suppress UVRAG expression to improve radiation cytotoxicity in pancreatic cancer. The predictive value of Klf10 in radiation response and the inverse correlation with UVRAG were confirmed in cohorts of pancreatic cancer patients. CONCLUSIONS: Klf10 is a potential biomarker in predicting and sensitizing radiation effect in pancreatic cancer.

TGF-beta-induced early gene-1 overexpression promotes oxidative stress protection and actin cytoskeleton rearrangement in human skin fibroblasts.

BACKGROUND: Transforming growth factor beta inducible early gene-1 (TIEG-1), a member of the Krüppel-like factor, was identified as a primary response gene for TGF-ß. The role of TIEG-1 in skin repair has been mainly addressed in vivo on TIEG-1 null mice model and the mechanism remains unexplored. METHODS: We investigated the modulation of TIEG-1 expression in normal human skin fibroblasts by either down-expressing or overexpressing the gene. We evaluated reactive oxygen species production and the cell viability of treated cells. The effect of TIEG-1 overexpression was monitored by wound healing assay and immunofluorescence staining of actin fibers organization and alpha-smooth muscle actin (α-SMA). Western blots were carried out to identify the level of expression or phosphorylation of key proteins such as cofilin, Rho GTPases, and p38 mitogen-activated protein kinase (p38 MAPK). RESULTS: TIEG-1 down-regulation had a deleterious effect on the cell viability. It was significantly reduced (65±5%) and exposure to ultraviolet further increased this effect (47±3%). By contrast, cells overexpressing TIEG-1 had a reduced reactive oxygen species production (75%) compared to control and mock-transfected cells. This overexpression also resulted in formation of actin stress fibers and increased α-SMA expression and an enhanced wound healing feature. RhoB GTPase was upregulated and phosphorylation of cofilin and p38 MAPK was observed. CONCLUSION: TIEG-1 overexpression in normal human skin fibroblasts results in improved resistance to oxidative stress, myofibroblast-like conversion that involved RhoB signaling pathway with cofilin and p38 MAPK proteins activation. GENERAL SIGNIFICANCE: This study enlightens the role of TIEG-1 role in skin biology.

Krüppel-like factor KLF10 regulates transforming growth factor receptor II expression and TGF-ß signaling in CD8+ T lymphocytes.

KLF10 has recently elicited significant attention as a transcriptional regulator of transforming growth factor-ß1 (TGF-ß1) signaling in CD4(+) T cells. In the current study, we demonstrate a novel role for KLF10 in the regulation of TGF-ß receptor II (TGF-ßRII) expression with functional relevance in antiviral immune response. Specifically, we show that KLF10-deficient mice have an increased number of effector/memory CD8(+) T cells, display higher levels of the T helper type 1 cell-associated transcription factor T-bet, and produce more IFN-γ following in vitro stimulation. In addition, KLF10(-/-) CD8(+) T cells show enhanced proliferation in vitro and homeostatic proliferation in vivo. Freshly isolated CD8(+) T cells from the spleen of adult mice express lower levels of surface TGF-ßRII (TßRII). Congruently, in vitro activation of KLF10-deficient CD8(+) T cells upregulate TGF-ßRII to a lesser extent compared with wild-type (WT) CD8(+) T cells, which results in attenuated Smad2 phosphorylation following TGF-ß1 stimulation compared with WT CD8(+) T cells. Moreover, we demonstrate that KLF10 directly binds to the TGF-ßRII promoter in T cells, leading to enhanced gene expression. In vivo viral infection with Daniel's strain Theiler's murine encephalomyelitis virus (TMEV) also led to lower expression of TGF-ßRII among viral-specific KLF10(-/-) CD8(+) T cells and a higher percentage of IFN-γ-producing CD8(+) T cells in the spleen. Collectively, our data reveal a critical role for KLF10 in the transcriptional activation of TGF-ßRII in CD8(+) T cells. Thus, KLF10 regulation of TGF-ßRII in this cell subset may likely play a critical role in viral and tumor immune responses for which the integrity of the TGF-ß1/TGF-ßRII signaling pathway is crucial.

dUev1a modulates TNF-JNK mediated tumor progression and cell death in Drosophila.

Loss of cell polarity cooperates with oncogenic Ras to induce JNK-dependent tumor growth and invasion. To identify additional genes that modulate tumor progression, we have performed a genetic screen in Drosophila and found that loss of dUev1a, the ortholog of mammalian Uev1, suppressed lgl(-/-)/Ras(V12) induced JNK-mediated tumor growth and invasion. Furthermore, loss of dUev1a suppressed TNF ortholog Eiger-induced JNK-mediated cell invasion and cell death. Finally, dUev1a cooperated with Bendless to activate JNK signaling through dTRAF2. Together, our data indicate that dUev1a encodes an essential component of the evolutionary conserved TNF-JNK signaling pathway that modulates tumor progression and cell death in metazoan.

Krüppel-like factor 10 upregulates the expression of cyclooxygenase 1 and further modulates angiogenesis in endothelial cell and platelet aggregation in gene-deficient mice.

Krüppel-like family is a group of zinc-finger transcription factors which play key regulatory roles in cellular growth, development, differentiation and vascularization. Recent studies have shown that one of the members, KLF10, is specifically involved in the process of angiogenesis by acting as a key transcriptional regulator of TGF-ß1 in pro-angiogenic cells differentiation and function. KLF10(-/-) mice also displayed impaired blood flow recovery after hindlimb ischemia. However, the mechanism of KLF10 induced angiogenesis is still not well understood. From ChIP-chip, which have been adopt to elucidate the novel target genes and signaling cascades of KLF10, COX-1 (also named as PTGS1) is one of the target genes that may be regulated by Klf10 through promoter binding. In order to investigate the function of KLF10/COX-1 axis, promoter activity, EMSA, ChIP-PCR and tube formation assays were serially performed. Our results demonstrated that KLF10 acts as a transcriptional activator on COX-1 promoter where overexpression of KLF10 induces COX-1 protein expression and mRNA expression in endothelial cells. It has been known that COX-1 is the key enzyme in prostaglandin biosynthesis which regulated angiogenesis in endothelial cells. Using tube formation assay, we further demonstrated that KLF10 overexpressed endothelial cells formed better organized three-dimensional tube structure in contrast to the control group did. To specifically investigate the role for KLF10 in angiogenesis, the its deficient mice exhibited decreased light transmission which represents the extend of platelet aggregation slowing down. Taken together, our results indicate an important role for KLF10 in angiogenesis through the activation of COX-1.

Transactivation of the TIEG1 confers growth inhibition of transforming growth factor-ß-susceptible hepatocellular carcinoma cells.

AIM: To investigate the role of transforming growth factor (TGF)-ß-inducible early gene 1 (TIEG1) in TGF-ß-induced growth inhibition in hepatocellular carcinoma (HCC) cells. METHODS: Human hepatocyte and HCC cell lines with varied susceptibilities to TGF-ß1 were tested by methylthiazoletetrazolium (MTT) assay. The expression changes of Smad2, Smad3, Smad4, Smad7, TIEG1 and TIEG2 gene following treatment with TGF-ß1 in a TGF-ß-sensitive hepatocyte cell line (MIHA), a TGF-ß-sensitive hepatoma cell line (Hep3B) and two TGF-ß-insensitive hepatoma cell lines (HepG2 and Bel7404) were examined. SiRNA targeting TIEG1 was transfected into Hep3B cells and the sensitivity of cells to TGF-ß1 was examined. Overexpression of TIEG1 was induced by lentiviral-mediated transduction in TGF-ß1-resistant hepatoma cell lines (Bel7404 and HepG2). MTT assay and 4',6-Diamidino-2-phenylindole staining were used to identify cell viability and apoptosis, respectively. The expression level of stathmin was measured by reverse transcriptase polymerase chain reaction and Western-blotting analysis, and stathmin promoter activity by TIEG1 was monitored by a luciferase reporter gene system. RESULTS: TIEG1 was significantly upregulated by TGF-ß1 in the TGF-ß1-sensitive HCC cell line, Hep3B, but not in the resistant cell lines. The suppression of TIEG1 by siRNAs decreased the sensitivity of Hep3B cells to TGF-ß1, whereas the overexpression of TIEG1 mediated growth inhibition and apoptosis in TGF-ß1-resistant HCC cell lines, which resembled those of TGF-ß1-sensitive HCC cells treated with TGF-ß1. Our data further suggested that stathmin was a direct target of TIEG1, as stathmin was significantly downregulated by TIEG1 overexpression, and stathmin promoter activity was inhibited by TIEG1 in a dose-dependent manner. CONCLUSION: Our data suggest that transactivation of TIEG1 conferred growth inhibition of TGF-ß-susceptible human HCC cells.

Neurturin evokes MAPK-dependent upregulation of Egr4 and KCC2 in developing neurons.

The K-Cl cotransporter KCC2 plays a crucial role in the functional development of GABA(A)-mediated responses rendering GABA hyperpolarizing in adult neurons. We have previously shown that BDNF upregulates KCC2 in immature neurons through the transcription factor Egr4. The effect of BDNF on Egr4 and KCC2 was shown to be dependent on the activation of ERK1/2. Here we demonstrate that the trophic factor neurturin can also trigger Egr4 expression and upregulate KCC2 in an ERK1/2-dependent manner. These results show that Egr4 is an important component in the mechanism for trophic factor-mediated upregulation of KCC2 in immature neurons involving the activation of specific intracellular pathways common to BDNF and Neurturin.

MAB-10/NAB acts with LIN-29/EGR to regulate terminal differentiation and the transition from larva to adult in C. elegans.

In Caenorhabditis elegans, a well-defined pathway of heterochronic genes ensures the proper timing of stage-specific developmental events. During the final larval stage, an upregulation of the let-7 microRNA indirectly activates the terminal differentiation factor and central regulator of the larval-to-adult transition, LIN-29, via the downregulation of the let-7 target genes lin-41 and hbl-1. Here, we identify a new heterochronic gene, mab-10, and show that mab-10 encodes a NAB (NGFI-A-binding protein) transcriptional co-factor. MAB-10 acts with LIN-29 to control the expression of genes required to regulate a subset of differentiation events during the larval-to-adult transition, and we show that the NAB-interaction domain of LIN-29 is conserved in Kruppel-family EGR (early growth response) proteins. In mammals, EGR proteins control the differentiation of multiple cell lineages, and EGR-1 acts with NAB proteins to initiate menarche by regulating the transcription of the luteinizing hormone ß subunit. Genome-wide association studies of humans and various studies of mouse recently have implicated the mammalian homologs of the C. elegans heterochronic gene lin-28 in regulating cellular differentiation and the timing of menarche. Our work suggests that human homologs of multiple C. elegans heterochronic genes might act in an evolutionarily conserved pathway to promote cellular differentiation and the onset of puberty.

TGF-ß1 signaling and Krüppel-like factor 10 regulate bone marrow-derived proangiogenic cell differentiation, function, and neovascularization.

Emerging evidence demonstrates that proangiogenic cells (PACs) originate from the BM and are capable of being recruited to sites of ischemic injury where they contribute to neovascularization. We previously determined that among hematopoietic progenitor stem cells, common myeloid progenitors (CMPs) and granulocyte-macrophage progenitor cells (GMPs) differentiate into PACs and possess robust angiogenic activity under ischemic conditions. Herein, we report that a TGF-ß1-responsive Krüppel- like factor, KLF10, is strongly expressed in PACs derived from CMPs and GMPs, ∼ 60-fold higher than in progenitors lacking PAC markers. KLF10(-/-) mice present with marked defects in PAC differentiation, function, TGF-ß responsiveness, and impaired blood flow recovery after hindlimb ischemia, an effect rescued by wild-type PACs, but not KLF10(-/-) PACs. Overexpression studies revealed that KLF10 could rescue PAC formation from TGF-ß1(+/-) CMPs and GMPs. Mechanistically, KLF10 targets the VEGFR2 promoter in PACs which may underlie the observed effects. These findings may be clinically relevant because KLF10 expression was also found to be significantly reduced in PACs from patients with peripheral artery disease. Collectively, these observations identify TGF-ß1 signaling and KLF10 as key regulators of functional PACs derived from CMPs and GMPs and may provide a therapeutic target during cardiovascular ischemic states.

TIEG1/KLF10 modulates Runx2 expression and activity in osteoblasts.

Deletion of TIEG1/KLF10 in mice results in a gender specific osteopenic skeletal phenotype with significant defects in both cortical and trabecular bone, which are observed only in female animals. Calvarial osteoblasts isolated from TIEG1 knockout (KO) mice display reduced expression levels of multiple bone related genes, including Runx2, and exhibit significant delays in their mineralization rates relative to wildtype controls. These data suggest that TIEG1 plays an important role in regulating Runx2 expression in bone and that decreased Runx2 expression in TIEG1 KO mice is in part responsible for the observed osteopenic phenotype. In this manuscript, data is presented demonstrating that over-expression of TIEG1 results in increased expression of Runx2 while repression of TIEG1 results in suppression of Runx2. Transient transfection and chromatin immunoprecipitation assays reveal that TIEG1 directly binds to and activates the Runx2 promoter. The zinc finger containing domain of TIEG1 is necessary for this regulation supporting that activation occurs through direct DNA binding. A role for the ubiquitin/proteasome pathway in fine tuning the regulation of Runx2 expression by TIEG1 is also implicated in this study. Additionally, the regulation of Runx2 expression by cytokines such as TGFß1 and BMP2 is shown to be inhibited in the absence of TIEG1. Co-immunoprecipitation and co-localization assays indicate that TIEG1 protein associates with Runx2 protein resulting in co-activation of Runx2 transcriptional activity. Lastly, Runx2 adenoviral infection of TIEG1 KO calvarial osteoblasts leads to increased expression of Runx2 and enhancement of their ability to differentiate and mineralize in culture. Taken together, these data implicate an important role for TIEG1 in regulating the expression and activity of Runx2 in osteoblasts and suggest that decreased expression of Runx2 in TIEG1 KO mice contributes to the observed osteopenic bone phenotype.

Early growth response 4 mediates BDNF induction of potassium chloride cotransporter 2 transcription.

A major event in the maturation of CNS GABAergic transmission is the qualitative change in GABA(A)-mediated responses from depolarizing to hyperpolarizing. In cortical regions, this is attributed to the increased expression of potassium chloride cotransporter 2b (KCC2b), the main isoform of the neuron-specific K-Cl cotransporter KCC2. We have previously shown that transcription factor early growth response 4 (Egr4) can activate the KCC2b promoter. Here we demonstrate that in immature hippocampal neurons BDNF robustly induces ERK1/2 (extracellular signal-regulated kinase 1/2)-dependent Egr4 expression and rapid Egr4-dependent activation of the KCC2b promoter. The subsequent increase in KCC2b mRNA contributes to the expression of total KCC2 protein levels. These results indicate that Egr4 is an important component in the mechanism of BDNF-dependent KCC2 gene regulation via the ERK1/2 pathway in immature neurons.

Functional role of KLF10 in multiple disease processes.

Since the discovery by this laboratory of the zinc finger transcription factor, KLF10, a member of the Krüppel-like family of transcription factors, there have been multiple publications regarding its functions and its immediate family members, in numerous cell types. KLF10 has been shown to be rapidly induced by TGFbeta1, 2, 3, E(2), epidermal growth factor, and bone morphogenetic protein-2. TGFbeta inducible early gene-1 activates the TGFbeta-Smad signaling pathway via repression of Smad 7 expression and activation of Smad 2 expression and activity. Overall, KLF10 has been implicated in cell differentiation, as a target gene for a variety of signaling pathways, and in serving as a potential marker for human diseases such as breast cancer, cardiac hypertrophy, and osteoporosis. Like other KLF members, KLF10 is expressed in specific cell types in numerous tissues and is known to be involved in repressing cell proliferation and inflammation as well as inducing apoptosis similar to that of TGFbeta. KLF10 binds to Sp-1-GC rich DNA sequences and can activate or repress the transcription of a number of genes. Overall, KLF10 has been shown to play a major role in the TGFbeta inhibition of cell proliferation and inflammation and induction of apoptosis, and its overexpression in human osteoblasts and pancreatic carcinoma cells mimics the actions of TGFbeta.

Transcription factors in long-term memory and synaptic plasticity.

Transcription is a molecular requisite for long-term synaptic plasticity and long-term memory formation. Thus, in the last several years, one main interest of molecular neuroscience has been the identification of families of transcription factors that are involved in both of these processes. Transcription is a highly regulated process that involves the combined interaction and function of chromatin and many other proteins, some of which are essential for the basal process of transcription, while others control the selective activation or repression of specific genes. These regulated interactions ultimately allow a sophisticated response to multiple environmental conditions, as well as control of spatial and temporal differences in gene expression. Evidence based on correlative changes in expression, genetic mutations, and targeted molecular inhibition of gene expression have shed light on the function of transcription in both synaptic plasticity and memory formation. This review provides a brief overview of experimental work showing that several families of transcription factors, including CREB, C/EBP, Egr, AP-1, and Rel, have essential functions in both processes. The results of this work suggest that patterns of transcription regulation represent the molecular signatures of long-term synaptic changes and memory formation.

Down-regulation of stathmin is required for TGF-beta inducible early gene 1 induced growth inhibition of pancreatic cancer cells.

Transforming growth factor-beta (TGF-beta) inducible early gene 1 (TIEG1) is known to induce apoptosis in TGF-beta sensitive pancreatic cancer cells, yet its effect on TGF-beta resistant cancer cells remains unclear. In this study, TIEG1 was found to induce apoptosis in TGF-beta resistant cancer cells and concurrently enhanced gemcitabine chemosensitivity. Down-regulation of stathmin was noted to associate with TIEG1 expression, whilst ectopic overexpression of stathmin prevented TIEG1 mediated growth inhibition of tumor cells. Small interfering RNAs targeting stathmin inhibited pancreatic cancer cell growth. These suggest that stathmin is a downstream target of TIEG1.

The E3 ubiquitin ligase Itch regulates expression of transcription factor Foxp3 and airway inflammation by enhancing the function of transcription factor TIEG1.

Transforming growth factor-beta (TGF-beta) signaling in naive T cells induces expression of the transcription factor Foxp3, a 'master' regulator of regulatory T cells (T(reg) cells). However, the molecular mechanisms leading to Foxp3 induction remain unclear. Here we show that Itch-/- T cells were resistant to TGF-beta treatment and had less Foxp3 expression. The E3 ubiquitin ligase Itch associated with and promoted conjugation of ubiquitin to the transcription factor TIEG1. Itch cooperated with TIEG1 to induce Foxp3 expression, which was reversed by TIEG1 deficiency. Functionally, 'TGF-beta-converted' T(reg) cells generated from TIEG1-deficient mice were unable to suppress airway inflammation in vivo. These results suggest TIEG and Itch contribute to a ubiquitin-dependent nonproteolytic pathway that regulates inducible Foxp3 expression and the control of allergic responses.

Reciprocal regulation of the human sterol regulatory element binding protein (SREBP)-1a promoter by Sp1 and EGR-1 transcription factors.

Sterol regulatory element binding protein (SREBP)-1a is a transcription factor that is highly expressed in actively growing cells, and is involved in the biosynthesis of cholesterol, fatty acids and phospholipids. We have mapped the minimal human SREBP-1a promoter region to 75bp upstream of the translation start site where we discovered a functional role for the 3 GC-boxes containing overlapping sites for the Sp1 and EGR-1 transcription factors. Intact SP1-binding sites are essential for promoter activity, whereas EGR-1 suppresses the transcription of the human SREBP-1a promoter. These results reveal a novel physiologically relevant transcriptional mechanism for the reciprocal regulation of the SREBP-1a expression.