Identification of the human alpha 6 integrin gene promoter
Identification of the human alpha 6 integrin gene promoter
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DOI：
10.1089/dna.1997.16.929
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发表时间：
1997-08-01
影响因子：
3.1
通讯作者：
Kramer, R
中科院分区：
文献类型：
--
作者：
Lin, CS;Chen, YQ;Kramer, R
α 6整合素亚基与β 1或β 4亚基偶联形成层粘连蛋白受体，α 6的表达是细胞类型特异性的，通常在上皮和内皮细胞中高水平表达。为了研究其基因调控，我们分离了一个包含人类α 6整合素基因启动子的基因组克隆，它包括3 kb的上游侧翼区，第一个外显子（385 bp）和9 kb的第一个内含子，α 6启动子从翻译起始密码子202个核苷酸的初级位点引导转录起始，与大多数其他整合素基因启动子不同，α 6启动子具有TATA box （GATAAA）。位于主要转录起始位点上游22个核苷酸处，TATA box上游190 bp的区域C和G核苷酸高度丰富（78%），包含多个Sp1和AP2结合序列。然而，完整的启动子活性（在SV40增强子存在的情况下）只需要TATA盒上游78 bp的这个富含C/ g的序列。在富含C/ g区域的稍上游是类固醇受体结合同源物和上皮细胞特异性E-pal序列，另一个可能的上皮细胞特异性结合序列（Ker1）在TATA box的下游被发现。在SV40增强子的存在下，α 6启动子的活性在原代角化细胞和HT1080纤维肉瘤细胞中增加了约4倍，在T47D乳腺癌细胞中增加了30倍，但在K562白血病细胞中未检测到α 6启动子的细胞类型特异性活性。基因组分析表明，在α 6阴性细胞中，DNA甲基化与α 6基因的沉默无关，DNA酶I足迹分析证实了Spl和AP2与其同源序列的结合，高α 6表达的HBL-100细胞的核提取物也与这些位点产生了显著的结合。提示这两个转录因子可能参与了α 6启动子的正向调控。
The alpha 6 integrin subunit couples with either the beta 1 or the beta 4 subunit to form a laminin receptor, alpha 6 expression is cell-type-specific and generally is present at high levels in epithelial and endothelial cells. To study its gene regulation, we isolated a genomic clone containing the human alpha 6 integrin gene promoter, It includes 3 kb of the upstream flanking region, the first exon (385 bp), and 9 kb of the first intron, The alpha 6 promoter directs transcription initiation from a primary site 202 nucleotides from the translation initiation codon, Unlike most other integrin gene promoters, the alpha 6 promoter has a TATA box (GATAAA), which is located 22 nucleotides upstream from the primary transcription initiation site, A 190-bp region upstream from the TATA box is highly rich (78%) in C and G nucleotides and contains several Sp1 and AP2 binding sequences. However, full promoter activity (in the presence of the SV40 enhancer) requires only 78 bp of this C/G-rich sequence upstream from the TATA box. Slightly upstream from the C/G-rich region are a steroid receptor binding homolog and an epithelial-cell-specific E-pal sequence, Another possible epithelial cell-specific binding sequence (Ker1) is found immediately downstream from the TATA box. Cell-type-specific activities of the promoter paralleled the alpha 6 mRNA levels in four tested cell lines, In the presence of the SV40 enhancer, alpha 6 promoter activity increased approximately four-fold in primary keratinocytes and in HT1080 fibrosarcoma cells and 30-fold in T47D breast carcinoma cells, but remained undetectable in K562 leukemia cells, Genomic analysis that compared alpha 6-expressing with non-alpha 6-expressing cells suggested that DNA methylation is not involved in the silencing of the alpha 6 gene in alpha 6-negative cells, DNase I footprint analysis confirmed the binding of Spl and AP2 to their cognate sequences, A nuclear extract of high-alpha 6-expressing HBL-100 cells also produced significant binding to these sites, suggesting that the two transcription factors are probably involved in the positive regulation of the alpha 6 promoter.