No abstract

The ZNF202 gene resides in a chromosomal region linked genetically to low high density lipoprotein cholesterol in Utah families. Here we show that the ZNF202 gene product is a transcriptional repressor that binds to elements found predominantly in genes that participate in lipid metabolism. Among its targets are structural components of lipoprotein particles (apolipoproteins AIV, CIII, and E), enzymes involved in lipid processing (lipoprotein lipase, lecithin cholesteryl ester transferase), and several genes involved in processes related to energy metabolism and vascular disease. Based on the linkage and apparent transcriptional function of ZNF202, we propose that ZNF202 is a candidate susceptibility gene for human dyslipidemia.

The zinc finger gene 202 (ZNF202) located within a hypoalphalipoproteinemia susceptibility locus on chromosome 11q23 is a transcriptional repressor of various genes involved in lipid metabolism. To provide further evidence for a functional linkage between ZNF202 and hypoalphalipoproteinemia, we investigated the effect of ZNF202 expression on ATP binding cassette transporter A1 (ABCA1) and ABCG1. ABCA1 is a key regulator of the plasma high density lipoprotein pool size, whereas ABCG1 is another mediator of cellular cholesterol and phospholipid efflux in human macrophage. We demonstrate here that the full-length ZNF202m1 isoform binds to GnT repeats within the promotors of ABCA1 (؊229/ ؊210) and ABCG1 (؊572/؊552). In past years, evidence has accumulated to suggest that a number of transcription factors play critical roles in the coordinate transcriptional regulation of genes involved in lipid metabolism (7,8). Linkage analysis in large Utah pedigrees led to the identification of a low HDL-cholesterol locus on chromosome 11q23 that is distinct from the apoAI/C-III/AIV gene cluster (9). This novel familial susceptibility locus for hypoalphalipoproteinemia contains the zinc finger protein 202 (ZNF202) originally described as a testis-specific transcription factor (9, 10). ZNF202 is expressed in two common splice variants. The m1 splice form encodes a full-length protein of 648 amino acids with an amino-terminal SCAN domain, a central KRAB repression domain, and 8 carboxyl-terminal Cys 2 -His 2 zinc finger motifs. The m3 splice form encodes a carboxylterminal-truncated protein of 133 amino acids that contains only the SCAN domain. The SCAN domain of ZNF202 has been shown to mediate selective protein oligomerization and the zinc finger motifs to bind to specific DNA elements (9, 11). Intriguingly, the ZNF202 DNA binding elements are present in promotors of various genes involved in lipid metabolism including apolipoproteins and lipid-processing enyzmes. ZNF202 has been therefore proposed to function as a transcriptional regulator of lipid metabolism (9).Based on this information, we tested the hypothesis of whether the ABC lipid transporters ABCA1 and ABCG1 are transcriptionally regulated by ZNF202. Our results provide evidence that ZNF202 acts as a transcriptional repressor of both ABCA1 and ABCG1 and, thus, establish a functional link between ZNF202 and hypoalphalipoproteinemia. EXPERIMENTAL PROCEDURESCell Culture-HepG2 and RAW264.7 cells (American Type Culture Collection) were cultured in Dulbecco's modified Eagle's medium (BioWhittaker) supplemented with 10% fetal calf serum (Sigma) in a 5% CO 2 atmosphere at 37°C. Cells (1 ϫ 10 6 cells/2-ml medium) were

The SCAN domain is described as a highly conserved, leucine-rich motif of approximately 60 amino acids found at the amino-terminal end of zinc finger transcription factors. Although no specific biological function has been attributed to the SCAN domain, its predicted amphipathic secondary structure led to the suggestion that this domain may mediate protein-protein associations. The SCAN or leucine-rich domain, originally identified by its homology with similar elements in several zinc finger transcription factors, consists of approximately 60 amino acids and is rich in leucine and glutamic acid residues (1). Most SCAN domain sequences are linked to Cys 2 -His 2 zinc finger motifs through their carboxyl-terminal end. Although the function of the SCAN domain has not yet been elucidated, the predicted amphipathic structure of the domain led to the suggestion that SCAN box elements have the capacity to interact with other proteins, in particular with components of the transcriptional machinery (1).The zinc finger protein ZNF202 1 is expressed in two common splice variants, here referred to as m1 and m3 (2). Whereas the m1-splice form encodes a full-length protein of 648 amino acids with a SCAN box, a KRAB repression domain, and eight Cys 2 -His 2 zinc finger motifs, the 133 amino acid product of the m3-splice form encompasses only the SCAN domain.2 These splice forms are conserved in the murine ZNF202 homolog, suggesting that the SCAN motif itself is an independent functional domain.3

The steroid compound cyproterone acetate was identified in a high-throughput screen for glucocorticoid receptor (GR) binding compounds. Cyproterone (Schering AG) is clinically used as an antiandrogen for inoperable prostate cancer, virilizing syndromes in women, and the inhibition of sex drive in men. Despite its progestin properties, cyproterone shares a similar pharmacological profile with the antiprogestin mifepristone (RU486; Roussel Uclaf SA). The binding affinities of cyproterone and RU486 for the GR and progesterone receptor were similar (K d , 15-70 nM). Both compounds were characterized as competitive antagonists of dexamethasone without intrinsic transactivating properties in rat hepatocytes (K i , 10 -30 nM). In osteosarcoma cells, RU486 revealed a higher potency than cyproterone acetate to prevent responses to dexamethasoneinduced GR transactivation and NFB transrepression. Upon administration to Sprague-Dawley rats, both compounds were found to be orally bioavailable and to inhibit transactivation of liver GR. Molecular docking of cyproterone acetate and RU486 into the homology model for the GR ligand binding domain illustrated overlapping steroid scaffolds in the binding pocket. However, in contrast to RU486, cyproterone lacks a bulky side chain at position C11␤ that has been proposed to trigger active antagonism of nuclear receptors by displacing the C-terminal helix of the ligand-binding domain, thereby affecting activation function 2. Cyproterone may therefore inhibit transactivation of the GR by a molecular mechanism recently described as passive antagonism. New therapeutic profiles may result from compounds designed to selectively stabilize the inactive and active conformations of certain nuclear receptors.Glucocorticoids are steroid hormones that are essential for normal growth and development, for liver and immune functions, and for mediating the stress response. Synthetic derivatives of glucocorticoids, such as dexamethasone, have immunosuppressive, anti-inflammatory, osteocatalytic, proteolytic, and hyperglycemic activities and are used to treat various pathological conditions (Sapolsky et al., 2000). The GR is a ligand-activated intracellular transcriptional regulator that is a member of the nuclear receptor superfamily. In the absence of a ligand, the GR is retained in the cytoplasm by association with chaperone proteins. Upon ligand binding, the GR dissociates from chaperones, dimerizes, and translocates into the nucleus. In the nucleus, the hormone-bound GR can modulate transcription of target genes by direct interaction with specific DNA sequences, called glucocorticoid response elements (GRE) in GR responsive promoters (Karin, 1998). Alternatively, activated GR can interact with nuclear factor B (NF-B) or with activator protein 1 (AP-1) to repress gene expression induced by these proinflammatory transcription factors. The anti-inflammatory and immunesuppressive properties of glucocorticoids have been largely attributed to the transrepression of NF-B and AP-1 function, whereas...