Ozono K, Yamagata M, Ohyama Y, Nakajima S
Department of Environmental Medicine, Osaka Medical Center and Research Institute for Maternal and Child Health, Izumi, Japan.
J Steroid Biochem Mol Biol. 1998 Sep;66(5-6):263-9. doi: 10.1016/s0960-0760(98)00055-7.
In a previous study, we identified the element which allows the maximum response to 1,25(OH)2D3 in concert with two vitamin D-responsive elements (VDREs) in the rat 25-hydroxyvitamin D3 24-hydroxylase gene promoter, and designated it an accessory element [Ohyama, Y., Ozono, K., Uchida, M., Yoshimura, M., Shinki, T., Suda, T. and Yamamoto, O. Functional assessment of two vitamin D-responsive elements in the rat 25-hydroxyvitamin D3 24-hydroxylase gene. J. Biol. Chem., 1996, 271, 30381-30385]. The accessory element located adjacent to the proximal VDRE is not capable of binding to the vitamin D receptor (VDR), while its nucleotide sequence resembles the consensus sequence of VDREs, direct repeat 3 (DR3). To clarify the difference between the accessory element and VDREs, the function of the accessory element was compared with that of VDREs. The mutated accessory elements with a single nucleotide substitution showed the capability of binding to the VDR in vitro. However, these mutants still did not act as a VDRE when driven by the heterologous SV40 promoter. The accessory element did not enhance the function of a cAMP-responsive element. The corresponding site of the accessory element in the human 24-hydroxylase is a DR4-type element, and this element did not function as an accessory element. These results indicate that a critical nucleotide sequence is necessary for the binding to the VDR and for mediating the vitamin D effect, and suggest the different regulation between the rat and human 24-hydroxylase gene.
在先前的一项研究中，我们确定了一种元件，它与大鼠25-羟维生素D3 24-羟化酶基因启动子中的两个维生素D反应元件（VDREs）协同作用，能对1,25(OH)2D3产生最大反应，并将其命名为辅助元件[小山洋、小园和树、内田真、吉村正、新木哲、须田彻、山本雄。大鼠25-羟维生素D3 24-羟化酶基因中两个维生素D反应元件的功能评估。《生物化学杂志》，1996年，271卷，30381 - 30385页]。位于近端VDRE附近的辅助元件不能与维生素D受体（VDR）结合，但其核苷酸序列类似于VDREs的共有序列，即直接重复序列3（DR3）。为了阐明辅助元件与VDREs之间的差异，我们将辅助元件的功能与VDREs的功能进行了比较。具有单个核苷酸取代的突变辅助元件在体外显示出与VDR结合的能力。然而，当由异源SV40启动子驱动时，这些突变体仍不能作为VDRE发挥作用。辅助元件不能增强cAMP反应元件的功能。人24-羟化酶中辅助元件的相应位点是一个DR4型元件，且该元件不能作为辅助元件发挥作用。这些结果表明，一个关键的核苷酸序列对于与VDR结合以及介导维生素D效应是必需的，并提示大鼠和人24-羟化酶基因之间存在不同的调控机制。
