Lavrovsky Y, Schwartzman M L, Levere R D, Kappas A, Abraham N G
Rockefeller University Hospital, New York, NY 10021.
Proc Natl Acad Sci U S A. 1994 Jun 21;91(13):5987-91. doi: 10.1073/pnas.91.13.5987.
Heme oxygenase (HO) is the rate-limiting enzyme in heme catabolism and its activity is induced by many agents, including its substrate heme, heavy metals, UV radiation, and other injurious oxidant conditions. We examined the presence of several regulatory elements in the promoter region of the human HO-1 gene which could possibly account for its induction in response to diverse agents or influences. Heme treatment increased both HO activity and HO-1 mRNA in the human erythroleukemic cell line K562. Electrophoretic mobility-shift assays of nuclear protein extracts from heme-treated and control cells with specific oligonucleotide probes containing binding sites for known transcription factors, including AP-1, AP-2, Sp1, NF-kappa B, CTF/NF1, TFIID, OKT1, and CREB, and oligonucleotides containing serum-, metal-, and glucocorticoid-responsive elements demonstrated a specific and marked increase in the NF-kappa B and AP-2 transcription factors and, to a lesser extent, an increase in AP-1. No significant increase in other transcription factors over the control, untreated cells was observed. DNase I footprint assays using purified transcription factors revealed the presence of NF-kappa B and AP-2 binding sites in the proximal part of the promoter region of the human HO-1 gene. Moreover, nucleotide sequence analysis of the HO-1 promoter region showed that the protected regions encompassed NF-kappa B and AP-2 consensus binding sites. The presence of regulatory sequences for the binding of transcription factors such as NF-kappa B and AP-2, whose activation is associated with the immediate response of the cell to an injury, may be an indication of the important role which HO-1 may play in defense mechanisms against tissue injury.
血红素加氧酶（HO）是血红素分解代谢中的限速酶，其活性可被多种物质诱导，包括其底物血红素、重金属、紫外线辐射以及其他有害的氧化应激条件。我们检测了人类HO-1基因启动子区域中几种调控元件的存在情况，这些元件可能解释其对多种物质或影响的诱导反应。血红素处理可增加人类红白血病细胞系K562中的HO活性和HO-1 mRNA水平。用含有已知转录因子（包括AP-1、AP-2、Sp1、NF-κB、CTF/NF1、TFIID、OKT1和CREB）结合位点的特异性寡核苷酸探针，以及含有血清、金属和糖皮质激素反应元件的寡核苷酸，对血红素处理和对照细胞的核蛋白提取物进行电泳迁移率变动分析，结果显示NF-κB和AP-2转录因子有特异性且显著的增加，AP-1也有较小程度的增加。与未处理的对照细胞相比，未观察到其他转录因子有显著增加。使用纯化转录因子的DNase I足迹分析揭示了人类HO-1基因启动子区域近端存在NF-κB和AP-2结合位点。此外，HO-1启动子区域的核苷酸序列分析表明，受保护区域包含NF-κB和AP-2共有结合位点。转录因子如NF-κB和AP-2的结合调控序列的存在，其激活与细胞对损伤的即时反应相关，这可能表明HO-1在组织损伤防御机制中可能发挥重要作用。
