Cornelius L A, Taylor J T, Degitz K, Li L J, Lawley T J, Caughman S W
Department of Dermatology, Emory University School of Medicine, Atlanta, Georgia.
J Invest Dermatol. 1993 Jun;100(6):753-8. doi: 10.1111/1523-1747.ep12476300.
Intercellular adhesion molecule-1 (ICAM-1), a cell-adhesion molecule critically involved in leukocyte trafficking and adherence, displays tissue-specific and cytokine-specific expression profiles. Although human dermal microvascular endothelial cells (HDMEC) constitutively express ICAM-1, keratinocytes (HK) do not. Interleukin-1 (IL-1) upregulates ICAM-1 expression in HDMEC, but fails to do so in either HK or A431, a human squamous carcinoma cell line, even though both have IL-1 receptors and express ICAM-1 on exposure to other cytokines. We have previously characterized a human ICAM-1 genomic clone that contains the 5' flanking transcriptional regulatory region. To test the hypothesis that tissue- and cytokine-specific ICAM-1 gene expression results from the interaction of constitutive and inducible tissue-specific trans-acting factors with distinct cis-elements of the ICAM-1 gene, various ICAM-1-based reporter gene (CAT) plasmids were constructed. Transcriptional activity of these various constructs was assessed after transient transfection into HDMEC and A431. A critical ICAM-1 region was identified that conferred enhanced expression of CAT in HDMEC and suppressed expression of CAT in A431. This same region further enhanced CAT expression in transfected HDMEC treated with IL-1 alpha, yet no such enhancement was seen with IL-1 treatment of identically transfected A431. However, treatment of A431 transfectants with IFN gamma did result in enhanced CAT expression, demonstrating reversal of A431 cell context suppression of the ICAM-1-based reporter gene construct. These data implicate the existence of both tissue- and cytokine-specific responsive elements in the 5' flanking region of the ICAM-1 gene and demonstrate that regulatory effects directed by such elements are dependent upon their cellular context. Moreover, they provide the basis for identification of specific cis-acting genetic elements, the trans-acting factors with which they interact, and the molecular mechanisms by which they regulate transcription of the ICAM-1 gene.
细胞间黏附分子-1（ICAM-1）是一种在白细胞迁移和黏附中起关键作用的细胞黏附分子，具有组织特异性和细胞因子特异性的表达谱。虽然人真皮微血管内皮细胞（HDMEC）组成性表达ICAM-1，但角质形成细胞（HK）却不表达。白细胞介素-1（IL-1）可上调HDMEC中ICAM-1的表达，但在HK或人鳞状癌细胞系A431中却不能，尽管这两种细胞都有IL-1受体且在暴露于其他细胞因子时会表达ICAM-1。我们之前鉴定了一个包含5'侧翼转录调控区的人ICAM-1基因组克隆。为了验证组织和细胞因子特异性ICAM-1基因表达是由组成性和诱导性组织特异性反式作用因子与ICAM-1基因不同顺式元件相互作用导致的这一假说，构建了各种基于ICAM-1的报告基因（CAT）质粒。将这些不同构建体瞬时转染到HDMEC和A431后，评估其转录活性。鉴定出一个关键的ICAM-1区域，该区域在HDMEC中可增强CAT的表达，而在A431中则抑制CAT的表达。同一区域在用IL-1α处理的转染HDMEC中进一步增强了CAT的表达，但在用IL-1处理相同转染的A431时却未观察到这种增强。然而，用IFNγ处理A431转染子确实导致了CAT表达增强，证明了A431细胞环境对基于ICAM-1的报告基因构建体抑制作用的逆转。这些数据表明ICAM-1基因5'侧翼区域存在组织和细胞因子特异性反应元件，并证明这些元件所介导的调控作用取决于它们所处的细胞环境。此外，它们为鉴定特定的顺式作用遗传元件、与之相互作用的反式作用因子以及它们调控ICAM-1基因转录的分子机制提供了基础。
