Doses of Sp1 expression plasmids. As shown in Figure 2A and

Doses of Sp1 expression plasmids. As shown in Figure 2A and 2B, both Luc and fluorescence protein assay results showed that co-expression of Sp1 significantly increased the MGARP promoter activity in a dose-dependent manner. To further confirm the involvement of Sp1 in MGARP promoter activation, we designed two oligo pairs that specifically targeted the Sp1 gene and generated two shRNA expression vectors, 630-RNAi and 1722-RNAi. As shown by western blotting, both 630-RNAi and 1722-RNAi could effectively reduce the expression of endogenous and exogenous Sp1, as compared to the control (pSilencer-scramble plasmid) (Figure 2C). Significantly, cotransfection of either 630-RNAi or 1722-RNAi with the pGL3-MGARP reporter led to a remarkable decrease in luciferase activity, in both the absence or presence of co-expressed Sp1 (Figure 2D). Moreover, RT-PCR results showed that downregulation of Sp1 by Microcystin-LR specific RNAi could reduce the endogenous MGARP gene expression (Figure 2E). These findings demonstrate that Sp1 is a critical transactivator for transcriptional activation of the MGARP promoter.Statistical AnalysisMultiple groups (at least 3 replicates for each test) of data for parallel reporter studies were analyzed based on the ratio of the firefly luciferase value to that of the renilla luciferase, using the SigmaPlot software for one Way ANOVA to generate specific P values. A value of P,0.05 was considered to be significant.Results Defining the Promoter Region of the Human MGARP GeneAfter performing a BLAST search of the NCBI database, the MGARP gene was found to be located on the minus strand of the Homo sapiens chromosome 4 genomic contig (The accession number of this genomic contig in GenBank is NW-922217.) Additionally, a 210 kb region upstream of the TSS was submitted for prediction of promoter properties. A typical CpG island, but no obvious TATA box, was identified in the proximal 23 kb region of the first exon (Figure 1A). For further definition, we compared the 23 kb promoter regions of three species and, as shown in Figure 1A, there are some key features of the promoterSp1 Activates the MGARP Promoter via Two GC-rich MotifsAs detailed above, two GC-boxes were identified in the proximal MGARP promoter centered at ,0 bp and ,260 bp, respectively. Each GC-box is clustered with two Sp1 binding elements. To clarify which GC rich motif is essential for Sp1mediated regulation, several reporter constructs were generated with or without the GC-boxes (Figure 3). Results of the reporter assay indicated that the following promoters carried basal activity: pGL3-MGARP (23 kb), pGL3-Box1 2, pGL3-Box1 and pGL3DEL2; and that the luciferase activity derived from these promoters was significantly enhanced by co-expressed Sp1. However, the following reporters suggested transcriptional silenceMGARP Is Regulated via Tandem Sp1 ElementsFigure 1. Bioinformatics analysis of the MGARP promoter. A. Promoter analysis comparing the 23 kb upstream region of the MGARP gene between three species (Homo sapiens, Pan troglodytes and Macaca I-BRD9 web mulatta). B. A summarized display of the 23 kb upstream region in the human MGARP promoter with predicted promoter and transcription factor (TF) binding sites. C. Luciferase (Luc) reporters driven by the 3 Kb MGARP promoter (pGL3-(23 kb)) and the promoter-less control (pGL3-Basic) were transfected into HEK-293T cells and analysis was carried out as described in Materials and Methods. *** represents p,0.001 and #represents p.0.05 (no.Doses of Sp1 expression plasmids. As shown in Figure 2A and 2B, both Luc and fluorescence protein assay results showed that co-expression of Sp1 significantly increased the MGARP promoter activity in a dose-dependent manner. To further confirm the involvement of Sp1 in MGARP promoter activation, we designed two oligo pairs that specifically targeted the Sp1 gene and generated two shRNA expression vectors, 630-RNAi and 1722-RNAi. As shown by western blotting, both 630-RNAi and 1722-RNAi could effectively reduce the expression of endogenous and exogenous Sp1, as compared to the control (pSilencer-scramble plasmid) (Figure 2C). Significantly, cotransfection of either 630-RNAi or 1722-RNAi with the pGL3-MGARP reporter led to a remarkable decrease in luciferase activity, in both the absence or presence of co-expressed Sp1 (Figure 2D). Moreover, RT-PCR results showed that downregulation of Sp1 by specific RNAi could reduce the endogenous MGARP gene expression (Figure 2E). These findings demonstrate that Sp1 is a critical transactivator for transcriptional activation of the MGARP promoter.Statistical AnalysisMultiple groups (at least 3 replicates for each test) of data for parallel reporter studies were analyzed based on the ratio of the firefly luciferase value to that of the renilla luciferase, using the SigmaPlot software for one Way ANOVA to generate specific P values. A value of P,0.05 was considered to be significant.Results Defining the Promoter Region of the Human MGARP GeneAfter performing a BLAST search of the NCBI database, the MGARP gene was found to be located on the minus strand of the Homo sapiens chromosome 4 genomic contig (The accession number of this genomic contig in GenBank is NW-922217.) Additionally, a 210 kb region upstream of the TSS was submitted for prediction of promoter properties. A typical CpG island, but no obvious TATA box, was identified in the proximal 23 kb region of the first exon (Figure 1A). For further definition, we compared the 23 kb promoter regions of three species and, as shown in Figure 1A, there are some key features of the promoterSp1 Activates the MGARP Promoter via Two GC-rich MotifsAs detailed above, two GC-boxes were identified in the proximal MGARP promoter centered at ,0 bp and ,260 bp, respectively. Each GC-box is clustered with two Sp1 binding elements. To clarify which GC rich motif is essential for Sp1mediated regulation, several reporter constructs were generated with or without the GC-boxes (Figure 3). Results of the reporter assay indicated that the following promoters carried basal activity: pGL3-MGARP (23 kb), pGL3-Box1 2, pGL3-Box1 and pGL3DEL2; and that the luciferase activity derived from these promoters was significantly enhanced by co-expressed Sp1. However, the following reporters suggested transcriptional silenceMGARP Is Regulated via Tandem Sp1 ElementsFigure 1. Bioinformatics analysis of the MGARP promoter. A. Promoter analysis comparing the 23 kb upstream region of the MGARP gene between three species (Homo sapiens, Pan troglodytes and Macaca mulatta). B. A summarized display of the 23 kb upstream region in the human MGARP promoter with predicted promoter and transcription factor (TF) binding sites. C. Luciferase (Luc) reporters driven by the 3 Kb MGARP promoter (pGL3-(23 kb)) and the promoter-less control (pGL3-Basic) were transfected into HEK-293T cells and analysis was carried out as described in Materials and Methods. *** represents p,0.001 and #represents p.0.05 (no.