Mutoh H, Kume K, Sato S, Kato S, Shimizu T
Department of Biochemistry, Faculty of Medicine, University of Tokyo, Japan.
Biochem Biophys Res Commun. 1994 Dec 15;205(2):1130-6. doi: 10.1006/bbrc.1994.2783.
We found that the expression of human platelet-activating factor receptor (PAFR) gene is differentially regulated by estrogen and TGF-beta 1. Primer extension analysis revealed that the levels of the PAFR transcript 2 were increased by estrogen, but decreased by TGF-beta 1 in the human stomach cancer cell line (JR-St cells) which expressed both functional endogenous PAFR transcript 1 (leukocyte-type) and transcript 2 (tissue-type). Both ligands did not affect the expression of intrinsic PAFR transcript 1. Furthermore, the response elements to estrogen and TGF-beta 1 in the PAFR promoter 2 were delineated by a transient expression assay using the chloramphenicol acetyltransferase (CAT) gene as a reporter in this cell line. A negative response element for TGF-beta 1 was mapped on the sequence from -90 bp to -81 bp, which has consensus sequence for TIE (TGF-beta 1 inhibitory element). Although consensus estrogen response element (AGGTCAnnnTGACCT) is not present in this promoter, the entire sequence comprising two AGGTCA half motifs spaced by 153 bp (from -257 bp to -93 bp) conferred weak but significant estrogen responsiveness. Thus, through these elements in the PAFR promoter 2, estrogen and TGF-beta 1 may regulate the PAFR gene to achieve a tissue-specific expression.
我们发现人血小板活化因子受体（PAFR）基因的表达受雌激素和转化生长因子β1（TGF-β1）的差异调节。引物延伸分析显示，在同时表达功能性内源性PAFR转录本1（白细胞型）和转录本2（组织型）的人胃癌细胞系（JR-St细胞）中，PAFR转录本2的水平因雌激素而升高，但因TGF-β1而降低。两种配体均不影响内源性PAFR转录本1的表达。此外，在该细胞系中，以氯霉素乙酰转移酶（CAT）基因为报告基因，通过瞬时表达试验确定了PAFR启动子2中雌激素和TGF-β1的反应元件。TGF-β1的负反应元件定位于-90 bp至-81 bp的序列上，该序列具有TIE（TGF-β1抑制元件）的共有序列。虽然该启动子中不存在共有雌激素反应元件（AGGTCAnnnTGACCT），但由两个间隔153 bp（从-257 bp至-93 bp）的AGGTCA半基序组成的整个序列赋予了微弱但显著的雌激素反应性。因此，通过PAFR启动子2中的这些元件，雌激素和TGF-β1可能调节PAFR基因以实现组织特异性表达。
