Iwakiri D, Podolsky D K
Gastrointestinal Unit, Department of Medicine, Massachusetts General Hospital and Harvard Medical School, 32 Fruit St., Boston, Massachusetts 02114, USA.
Am J Physiol Gastrointest Liver Physiol. 2001 Jun;280(6):G1114-23. doi: 10.1152/ajpgi.2001.280.6.G1114.
Intestinal trefoil factor (ITF) is selectively expressed in intestinal goblet cells. Previous studies identified cis-regulatory elements in the proximal promoter of ITF, but these were insufficient to recapitulate the exquisite tissue- and cell-specific expression of native ITF in vivo. Preliminary studies suggested that goblet cell-specific expression of murine ITF requires elements far upstream that include a silencer element that effectively prevents ITF expression in non-goblet cells. Transient transfection studies using native or mutant ITF 5'-flanking sequences identified a region that restores expression in goblet cells. This element, designated goblet cell silencer inhibitor (GCSI) element, enables human and murine goblet cell-like cell lines to override the silencing effect of more proximal elements. The GCSI has no intrinsic enhancer activity and regulates expression only when the silencer element is present. Ligation of GCSI and silencer elements to sucrase-isomaltase conferred goblet cell-specific expression. Goblet cells but not non-goblet cells possess a nuclear protein that binds to the GCSI regulatory element (GCSI binding protein; GCSI-BP). Both transient transfection and gel mobility shift assay studies localize the GCSI and GCSI-BP to -2216 to -2204. We conclude that goblet cell-specific transcription of ITF in vivo depends on a regulatory element designated GCSI.
肠三叶因子（ITF）在肠道杯状细胞中选择性表达。先前的研究在ITF近端启动子中鉴定出顺式调控元件，但这些元件不足以在体内重现天然ITF精确的组织和细胞特异性表达。初步研究表明，小鼠ITF的杯状细胞特异性表达需要上游远端元件，其中包括一个能有效阻止ITF在非杯状细胞中表达的沉默元件。使用天然或突变的ITF 5'-侧翼序列进行的瞬时转染研究确定了一个能在杯状细胞中恢复表达的区域。这个元件被命名为杯状细胞沉默抑制剂（GCSI）元件，它能使人和小鼠的杯状细胞样细胞系克服更近端元件的沉默效应。GCSI没有内在的增强子活性，仅在沉默元件存在时调节表达。将GCSI和沉默元件连接到蔗糖酶-异麦芽糖酶上可赋予杯状细胞特异性表达。杯状细胞而非非杯状细胞拥有一种能与GCSI调控元件结合的核蛋白（GCSI结合蛋白；GCSI-BP）。瞬时转染和凝胶迁移率变动分析研究均将GCSI和GCSI-BP定位到-2216至-2204区域。我们得出结论，体内ITF的杯状细胞特异性转录依赖于一个名为GCSI的调控元件。
