骨桥蛋白的制备及功能研究

目的　探讨骨桥蛋白 (OPN)对血管平滑肌细胞是否具有促黏附及趋化作用。方法　从大鼠源性血管平滑肌细胞的细胞培养基中纯化OPN ,制备家兔抗OPN多克隆抗体。用酶联免疫吸附及迁移分析方法测定OPN对血管平滑肌细胞的影响。结果　骨桥蛋白能够促进血管平滑肌细胞发生黏附 ,且其促黏附功能呈浓度依赖性。黏附率在实验开始后 90～ 1 2 0min区段达到最高。与对照相比 ,OPN刺激血管平滑肌细胞的迁移距离明显增加。结果　骨桥蛋白是血管平滑肌细胞的黏附、迁移活化因子     

Identification and characterization of the hypoxia-responsive element in human stanniocalcin-1 gene

In this study, we aimed to identify the hypoxia-inducible factor-1 (HIF-1) binding motif in human STC1 gene promoter and to characterize the associated gene transactivation mechanism. Using normoxic human nasopharyngeal cancer cells (CNE2), we manipulated the stability of HIF-1α protein by overexpressing HIF-1α or the silencing of prolyl hydroxylase-2 (PHD2), to illustrate HIF-1 activation of STC1 promoter-driven luciferase activity. Subsequently luciferase activities of the deletion and mutated STC1 promoter constructs were investigated in HIF-1 overexpressed cells. The data revealed the presence of an authentic HRE motif in STC1 gene. This result was further supported by the chromatin immunoprecipitation (ChIP) assay. Using a similar experimental treatment, however, had no significant effect on the expression level of STC1 mRNA and protein. Moreover the activation of STC1 expression can be restored by the silencing of “factor inhibiting HIF-1” (FIH-1) in either HIF-1 overexpressed or PHD2 silenced cells. The data implied that the HIF-1-mediated STC1 gene expression required the recruitment of p300. This presumption was confirmed by the use of p300 inhibitor, chetomin and HIF-1α/p300 re-ChIP assay. Collectively our data provide the first evidence to show that STC1 is a FIH-inhibited gene with a functional HRE motif located at the upstream region between −2322/−2335. The data support the need for further investigation to reveal if STC1 can be used as a novel tumor marker for HIF-1 induction and for the monitoring of anti-angiogenic therapy.     

Identification of a retinoid receptor response element in the human aldehyde dehydrogenase-2 promoter

BACKGROUND: The human aldehyde dehydrogenase-2 promoter contains sites that bind members of the nuclear receptor family, and one (designated FP330-3') is predicted to bind retinoic acid receptors. METHODS: Binding of retinoid receptors to the FP330-3' oligonucleotide duplex and point mutations thereof was assayed using electrophoretic mobility shift assays. The function of the promoter element was determined in transfection assays. RESULTS: Heterodimers of retinoic acid receptor (RAR)alpha, beta, and gamma with retinoid X receptor (RXR)alpha bound the FP330-3' site. Mutagenesis of the FP330-3' site suggested that either the upstream DR-5 or downstream DR-1 could mediate binding of RAR/RXR. FP330-3' oligonucleotide duplexes were not bound by in vitro translated RXR homodimers but weakly competed with a synthetic DR-1 oligonucleotide duplex for binding by RXR. A reporter construct carrying four copies of the FP330-3' element was induced by cotransfection of rat hepatoma cells with a construct encoding RARalpha, when the RAR-specific ligand AM580 was present. Each of the three RXR isoforms alpha, beta, and gamma stimulated the expression of reporter constructs containing the FP330-3' sites in a 9-cis retinoic acid-dependent fashion in cells in culture. This was confirmed in the case of RXRalpha using the RXR-specific ligand methoprene. CONCLUSION: The human aldehyde dehydrogenase-2 promoter contains a retinoid response element, which may contribute to regulation of the gene.     

Identification and characterization of a response element in the EGFR promoter that mediates transcriptional repression by 1,25-dihydroxyvitamin D3 in breast cancer cells

Reduction of epidermal growth factor receptor (EGFR) mRNA and protein by 1,25-dihydroxyvitamin D3 has been documented in MCF7, T47D, and BT549 breast cancer cells. In the present report, functional mapping of the EGFR promoter in BT549 cells has revealed a sequence of DNA between nucleotide positions -536 and -478 that resembles a consensus vitamin D response element (VDRE) and confers a vitamin D response upon both the homologous and a minimal heterologous promoter. In vitro footprinting and gel shift assays demonstrate the presence of an unidentified nuclear factor that is required for strong binding of the vitamin D receptor (VDR) to this putative VDRE. An Sp1 binding site was also identified in close proximity and shown to bind Sp1 from nuclear extract. Mutational analysis and functional studies using a minimal heterologous promoter provide evidence that the VDR in concert with an unknown nuclear partner mediates basal EGFR repression through displacement of Sp1 which is augmented in the presence of a ligand.