Zha Shan, Isaacs William B
Brady Urological Institute, Johns Hopkins Medical Institutions, Baltimore, Maryland, USA.
Mol Cancer Res. 2005 Feb;3(2):110-8. doi: 10.1158/1541-7786.MCR-04-0178.
Alpha-methylacyl-CoA racemase (AMACR), an enzyme involved in branched-chain fatty acid beta-oxidation that is normally expressed at high levels in human liver, is specifically and consistently overexpressed at both mRNA and protein levels in human prostate cancer and potentially other cancer types. To characterize the mechanisms underlying transcriptional regulation of AMACR at the genetic and epigenetic levels, we performed a series of methylation and reporter assays in prostate cancer tissues and cell lines. The results ruled out altered methylation patterns as the cause of overexpression in prostate cancer cells. However, promoter deletion analysis identified an 8-bp nonclassic CCAAT enhancer element located approximately 80 bp upstream of the transcriptional initiation site that is responsible for AMACR expression in both prostate cancer cell lines and cell lines of liver origin. Deletion or mutation of this element completely abolished AMACR promoter activity. Ectopic expression of CCAAT/enhancer binding protein beta increased luciferase activity driven by a wild-type AMACR promoter sequence but not by the sequence in which the putative CCAAT/enhancer binding protein binding element had been mutated. These results implicate a nonclassic CCAAT enhancer element in the AMACR gene promoter as playing a critical role in the regulation of AMACR gene expression.
α-甲基酰基辅酶A消旋酶（AMACR）是一种参与支链脂肪酸β-氧化的酶，在人类肝脏中通常高水平表达，在人类前列腺癌以及可能的其他癌症类型中，其mRNA和蛋白质水平均有特异性且持续的过表达。为了在基因和表观遗传水平上表征AMACR转录调控的潜在机制，我们在前列腺癌组织和细胞系中进行了一系列甲基化和报告基因检测。结果排除了甲基化模式改变是前列腺癌细胞中过表达原因的可能性。然而，启动子缺失分析确定了一个位于转录起始位点上游约80 bp处的8 bp非经典CCAAT增强子元件，该元件负责前列腺癌细胞系和肝脏来源细胞系中AMACR的表达。该元件的缺失或突变完全消除了AMACR启动子活性。CCAAT/增强子结合蛋白β的异位表达增加了由野生型AMACR启动子序列驱动的荧光素酶活性，但不增加假定的CCAAT/增强子结合蛋白结合元件已发生突变的序列所驱动的荧光素酶活性。这些结果表明，AMACR基因启动子中的非经典CCAAT增强子元件在AMACR基因表达调控中起关键作用。
