Hori T, Hosokawa M
Laboratory of Drug Metabolism and Biopharmaceutics, Faculty of Pharmaceutical Sciences, Chiba Institute of Science, Choshi, Japan.
Xenobiotica. 2010 Feb;40(2):119-28. doi: 10.3109/00498250903431794.
Carboxylesterase 1A1 (CES1A1) efficiently catalyses the hydrolysis of a substrate containing ester, amide, or thioester bonds. It is expressed at a high level in the human liver, but at a low level in the human kidney. In this study, we found the cause of this tissue-specific expression of the CES1A1 gene using 5-aza-2'-deoxycytidine (5-aza-dC) and bisulfite sequencing. Treatment of HEK293 cells, human embryonic kidney cells not expressing the CES1A1 gene, with 5-aza-dC caused dramatic expression of the CES1A1 gene. Bisulfite sequencing revealed that the region around the transcription start site (TSS) of the CES1A1 gene was almost entirely methylated in HEK293 cells, whereas the region was almost entirely unmethylated in HepG2 cells, human hepatoma cells. The hypomethylated DNA molecules for the region were observed in HEK293 cells treated with 5-aza-dC. In the genome obtained from the kidney, the region downstream of the TSS was methylated compared with that obtained from the liver. From these findings, it can be concluded that DNA methylation is involved in CES1A1 gene expression and that the difference between CES1A1 gene expression in the human kidney and that in the human liver may arise from the difference in DNA methylation levels in the region around the TSS.
羧酸酯酶1A1（CES1A1）能高效催化含有酯键、酰胺键或硫酯键的底物的水解反应。它在人类肝脏中高表达，但在人类肾脏中低表达。在本研究中，我们使用5-氮杂-2'-脱氧胞苷（5-aza-dC）和亚硫酸氢盐测序法找到了CES1A1基因这种组织特异性表达的原因。用5-aza-dC处理不表达CES1A1基因的人类胚胎肾细胞HEK293细胞，会使CES1A1基因显著表达。亚硫酸氢盐测序显示，CES1A1基因转录起始位点（TSS）周围区域在HEK293细胞中几乎完全甲基化，而在人类肝癌细胞HepG2细胞中该区域几乎完全未甲基化。在用5-aza-dC处理的HEK293细胞中观察到了该区域的低甲基化DNA分子。在从肾脏获得的基因组中，与从肝脏获得的基因组相比，TSS下游区域发生了甲基化。从这些发现可以得出结论，DNA甲基化参与了CES1A1基因的表达，并且人类肾脏和人类肝脏中CES1A1基因表达的差异可能源于TSS周围区域DNA甲基化水平的差异。
