Into cholesteryl ester, was up-regulated by rifampicin, though the expression of ACAT1 was not affected (Figure 3F and Figure 6A). It remains to be determined whether LCAT is a direct Title Loaded From File target gene of PXR. SCD1 1317923 is a d-9 desaturase and is the rate-limiting Title Loaded From File enzyme responsible for converting palmitic (16:0) and stearic acid (18:0) to palmitoleic (16:1) and oleic (18:1) acids, respectively [24]. SCD1 gene expression is altered by a remarkable number of nutrients, hormones and environmental factors [24,25]. Several nuclear receptors, such as LXRs [26], TR [27] and PPARa [28] were involved in the regulation of SCD1. SCD1 expression is positively regulated by LXR, either directly through the binding of LXR to an LXR response element in the SCD1 gene promoter, or indirectly through LXR-mediated activation of SREBP-1c transcription 11967625 [34,35,36]. Dietary carbohydrates can increase hepatic SCD1 gene expression through both SREBP-1c-dependent and independent mechanisms [37]. Activation of the cellular immune response via toll-like receptor 2 also increases the transcription of SCD1, potentially via the nuclear factor kB elements in the SCD1 gene promoter [38]. Our transcription factor binding sites screen on the human SCD1 gene promoter indicated several potential PXR bindingelements (PXREs) in the 2000-bp region of upstream of the transcription start site (Figure 7A). Our promoter analysis results have provided evidence to support SCD1 as a direct transcriptional target of PXR. Both pharmacological (Rifampicin) and genetic (VP-PXR) activation of PXR were sufficient to induce SCD1 expression (Figure 7B and 7C). A DR7 type element (CTGCCAcgtctccCTGCCA) at the -338 bp to -320 bp of SCD1 promoter was identified as a PXRE, where PXR directly bound to this element and activated SCD1 transcription upon activation. To our knowledge, this is the first report that PXR can bind to a DR7 type of PXRE. PXR has been reported to bind to DR4 type (CYP3As [39] and S14 [20]), ER6 type (CYP3A4), and DR3 type (CD36 [23]) of PXREs. In summary, we showed that PXR activation in the human hepatoma HepG2 cells induced lipid accumulation though upregulation of several hepatic lipogenic genes. The human SCD1 was identified to be a direct transcriptional target of PXR via a novel DR7 type PXRE on the SCD1 gene promoter.AcknowledgmentsWe are grateful to Dr. Richard G. Pestell (Georgetown University) for his plasmid gifts.Author ContributionsConceived and designed the experiments: YZ. Performed the experiments: JZ YW BH. Analyzed the data: JZ YZ. Contributed reagents/materials/ analysis tools: MH WX. Wrote the paper: JZ YZ.
Adenylate Kinase (AdK) is a small ubiquitous enzyme that catalyzes the reversible phosphoryl-transfer reaction ATPzAMP<2ADP and plays an important role in cell signaling [1,2] and energy metabolism [1]. Malfunction of AdKs may cause human diseases such as nucleotide diphosphate kinase deficiency [3], hematopoietic defect [4], and hemolytic anemia [5]. Similar to many enzymes, the catalytic cycle of AdK involves large-scale conformational change of the protein. Indeed, AdK structures in different conformational states have been captured in crystallography and NMR experiments [6?2]. In particular, the ligand-free AdK conformation appears to be in an open state [7], in contrast to the nucleotide-bound crystal structure in an apparently closed state [6]. Structurally, AdK is composed of three domains: an ATP-binding domain (LID: residues 122?59), an AMP-binding dom.Into cholesteryl ester, was up-regulated by rifampicin, though the expression of ACAT1 was not affected (Figure 3F and Figure 6A). It remains to be determined whether LCAT is a direct target gene of PXR. SCD1 1317923 is a d-9 desaturase and is the rate-limiting enzyme responsible for converting palmitic (16:0) and stearic acid (18:0) to palmitoleic (16:1) and oleic (18:1) acids, respectively [24]. SCD1 gene expression is altered by a remarkable number of nutrients, hormones and environmental factors [24,25]. Several nuclear receptors, such as LXRs [26], TR [27] and PPARa [28] were involved in the regulation of SCD1. SCD1 expression is positively regulated by LXR, either directly through the binding of LXR to an LXR response element in the SCD1 gene promoter, or indirectly through LXR-mediated activation of SREBP-1c transcription 11967625 [34,35,36]. Dietary carbohydrates can increase hepatic SCD1 gene expression through both SREBP-1c-dependent and independent mechanisms [37]. Activation of the cellular immune response via toll-like receptor 2 also increases the transcription of SCD1, potentially via the nuclear factor kB elements in the SCD1 gene promoter [38]. Our transcription factor binding sites screen on the human SCD1 gene promoter indicated several potential PXR bindingelements (PXREs) in the 2000-bp region of upstream of the transcription start site (Figure 7A). Our promoter analysis results have provided evidence to support SCD1 as a direct transcriptional target of PXR. Both pharmacological (Rifampicin) and genetic (VP-PXR) activation of PXR were sufficient to induce SCD1 expression (Figure 7B and 7C). A DR7 type element (CTGCCAcgtctccCTGCCA) at the -338 bp to -320 bp of SCD1 promoter was identified as a PXRE, where PXR directly bound to this element and activated SCD1 transcription upon activation. To our knowledge, this is the first report that PXR can bind to a DR7 type of PXRE. PXR has been reported to bind to DR4 type (CYP3As [39] and S14 [20]), ER6 type (CYP3A4), and DR3 type (CD36 [23]) of PXREs. In summary, we showed that PXR activation in the human hepatoma HepG2 cells induced lipid accumulation though upregulation of several hepatic lipogenic genes. The human SCD1 was identified to be a direct transcriptional target of PXR via a novel DR7 type PXRE on the SCD1 gene promoter.AcknowledgmentsWe are grateful to Dr. Richard G. Pestell (Georgetown University) for his plasmid gifts.Author ContributionsConceived and designed the experiments: YZ. Performed the experiments: JZ YW BH. Analyzed the data: JZ YZ. Contributed reagents/materials/ analysis tools: MH WX. Wrote the paper: JZ YZ.
Adenylate Kinase (AdK) is a small ubiquitous enzyme that catalyzes the reversible phosphoryl-transfer reaction ATPzAMP<2ADP and plays an important role in cell signaling [1,2] and energy metabolism [1]. Malfunction of AdKs may cause human diseases such as nucleotide diphosphate kinase deficiency [3], hematopoietic defect [4], and hemolytic anemia [5]. Similar to many enzymes, the catalytic cycle of AdK involves large-scale conformational change of the protein. Indeed, AdK structures in different conformational states have been captured in crystallography and NMR experiments [6?2]. In particular, the ligand-free AdK conformation appears to be in an open state [7], in contrast to the nucleotide-bound crystal structure in an apparently closed state [6]. Structurally, AdK is composed of three domains: an ATP-binding domain (LID: residues 122?59), an AMP-binding dom.
