Early growth response protein 1 acts as an activator of SOX18 promoter

Abstract

Sex-determining region Y box 18 (Sox18/SOX18) gene is an important regulator of vascular development playing a role in endothelial cell specification or differentiation, angiogenesis and atherogenesis. The aim of this study was to perform comprehensive functional characterization of the human SOX18 promoter, including determination of transcription start point (tsp) and identification of control elements involved in the regulation of SOX18 gene expression, with an emphasis on angiogenesis-related transcription factors. Analyses were performed in HeLa cells, representing a tumor cell line, and in EA.hy926 cells used as an endothelial model system. We have determined unique tsp of SOX18 gene, located 172 nucleotides upstream from ATG codon. Further, we have shown that SOX18 promoter region, -726 to -89 bp relative to tsp, contains positive cis-regulatory element(s) that stimulates SOX18 promoter activity, while region -89 to + 166 represents the minimal promoter. Within this region we have recognized the presence of essential element(s), positioned from -89 to +29, which harbors cluster of three putative early growth response 1 (EGR1) binding sites. By in vitro binding assays and functional analyses we have shown that these three putative binding sites are functionally relevant and sufficient for EGR1-induced SOX18 transcription. Mutations of these binding sites significantly impaired activity of the SOX18 promoter, particularly in EA.hy926 cells, indicating the importance of these regulatory elements for SOX18 promoter activity in endothelial setting. By data presented in this study, we have established SOX18 as a novel target gene regulated by EGR1 transcription factor, thus providing the first functional link between two transcription factors previously shown to be involved in the control of angiogenesis.

Chlorpromazine activates p21Waf1/Cip1gene transcription via early growth response-1 (Egr-1) in C6 glioma cells

“…Waf1/Cip1 , p53, TGFβ1, PTEN, fibronectin, Gadd45, and Sox18 (Virolle et al, 2001;Krones-Herzig et al, 2003;Thyss et al, 2005;Baron et al, 2006;Petrovic et al, 2010). Thus, Egr-1 appears to be a tumor suppressor.…”

VEGF and TNF up-regulate, NSAID down-regulate SOX18 protein level in HUVEC

“…Also, VEGF treatment stimulated the accumulation of EGR1 in the nucleus within 60 minutes [30]. The functional link between VEGF and EGR1 is particularly interesting since we have recently shown that SOX18 promoter activity is positively regulated by EGR1 [21]. Thus, it would be interesting to investigate whether EGR1 mediates the SOX18 expression elicited by VEGF, thereby giving a novel insight into possible functional relation between EGR1 and SOX18 during angiogenesis.…”

“…In addition to RNA isolated from HUVEC, we included in this analysis RNAs isolated from HeLa cells and EA.hy926 endothelial cells. Namely, we used RT-PCR method in order to analyze the expression of SOX18 gene in HUVEC, while HeLa and EA.hy926 cells served as positive controls, for which we have previously shown to express SOX18 [19,21]. As presented at Figure 1, after 12 cycles of amplification no products could be detected for either SOX18 or GAPDH gene.…”

“…Since we have shown previously that transcription factor Sp3 acts as a repressor of SOX18 promoter activity [20], we hypothesize that TNF induced SOX18 expression is, at least in part, associated with inhibited binding of Sp3. In addition, the expression of transcription factor EGR1, shown to be able to up-regulate SOX18 promoter activity [21], is also stimulated by TNF [41]. …”

“…We have characterized the promoter region of SOX18 and demonstrated that specificity protein 3 (Sp3), zinc finger binding protein 89 (ZBP-89) and nuclear factor Y (NF-Y) are involved in the regulation of SOX18 gene expression in the HeLa cell line [19,20]. Furthermore, in a search for transcription factors involved in regulation of SOX18 gene expression that are also relevant for the control of angiogenesis, we have recently identified early growth response 1 (EGR1) as an activator of SOX18 promoter activity [21].…”