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从乳腺癌cDNA文库中分离出的乳腺癌特异性基因1(BCSG1,breastcancer-specificgene1)又称Synucleinγ,其表达蛋白广泛分布在神经系统的神经元突触前末稍.除神经系统外,正常乳腺组织或良性病变中BCSG1几乎不表达,而多数浸润性乳腺癌、卵巢癌等肿瘤组织中表达异常增高.BCSG1的异常表达与肿瘤细胞的生长、浸润及转移相关.为了解BCSG1的转录调控机制及转录因子对调控的影响,用含启动子的BCSG1片段构建了不同长度的3′端缺失片段、删除Sp1片段以及突变转录激活蛋白1(AP1,activatorprotein)位点的BCSG1启动子报告质粒,并选用乳腺癌细胞系进行瞬时转染,分析BCSG1启动子活性变化.研究发现,BCSG1启动子5′端区序列可决定BCSG1的基础转录活性,并受Sp1位点调控;在BCSG1蛋白阴性的乳腺癌细胞中,pGL3-1553的活性显著降低;在HepG2肝癌细胞中,pGL3-1759的活性显著降低;内含子1中AP1位点突变或缺失使启动子转录活性明显降低;c-jun和c-fos,及cAMP效应器结合蛋白(CREB,cyclinAMP-responsiveelementbinding)可以显著增强BCSG1启动子的活性.这些结果表明,BCSG1的异常表达可能受多种因素影响,5′端区序列及Sp1位点决定BCSG1启动子的基础活性;外显子1中含有可能影响BCSG1异常表达的关键序列;决定细胞特异性表达的序列可能存在于内含子1中;内含子中AP1结合位点可以调控BCSG1启动子的活性.
Breast cancer-specific gene 1 (BCSG1, breastcancer-specific gene1), also known as Synucleinγ, is widely distributed in the neuronal synaptic terminals of the nervous system. In addition to the nervous system, the normal breast BCSG1 is almost not expressed in tissues or benign lesions, while in most invasive breast cancer and ovarian cancer, abnormal expression of BCSG1 is associated with tumor cell growth, invasion and metastasis.In order to understand the mechanism of BCSG1 transcriptional regulation and BCSG1 fragment containing promoter was used to construct the 3 ’deletion fragment of different length and the Spl fragment and BCSG1 promoter reporter plasmid of AP1 (activatorprotein) site were deleted and selected Breast cancer cell lines were transiently transfected to analyze BCSG1 promoter activity changes.The study found that BCSG1 promoter 5 ’end region sequence can determine the basic transcription activity of BCSG1 and Sp1 site regulation; BCSG1 protein-negative breast cancer cells , The activity of pGL3-1553 was significantly decreased; the activity of pGL3-1759 was significantly decreased in HepG2 hepatoma cells; the mutation or deletion of AP1 site in intron 1 C-fos and cAMP-responsive element binding protein (CREB, cyclinAMP-responsiveelementbinding) can significantly enhance the activity of BCSG1 promoter.These results show that the abnormal expression of BCSG1 may be affected by a variety of factors The 5 ’end region and Sp1 locus determine the basic activity of BCSG1 promoter. Exon 1 contains the key sequence that may affect the abnormal expression of BCSG1. The sequence that determines cell-specific expression may exist in intron 1. The AP1 binding site in the intron can regulate the activity of the BCSG1 promoter.