Smith L T, Hohaus S, Gonzalez D A, Dziennis S E, Tenen D G
Department of Medicine, Beth Israel Hospital, Harvard Medical School, Boston, MA 02215, USA.
Blood. 1996 Aug 15;88(4):1234-47.
Cytokines, important for lineage commitment and differentiation during hematopoiesis, exert their influence by binding specific receptors. Receptor expression is tightly regulated and examining the factors that govern their expression will allow better understanding of the events that determine lineage commitment. The granulocyte colony-stimulating factor (G-CSF) receptor is expressed exclusively in myeloid cells and the placenta. We show here that the G-CSF receptor transcription start site is identical in each of these tissues. A 1,391-bp fragment of the G-CSF receptor promoter is both active in myeloid cell lines and tissue specific. We have also found two regions that are important for G-CSF receptor promoter activity. One region, located at bp -49, contains a GCAAT site that specifically binds the C/EBP alpha transcription factor in myeloid nuclear extracts. Mutation of this site prevents C/EBP alpha binding and reduces promoter activity by 60%. The other functionally important region of the G-CSF receptor promoter is in the 5' untranslated region, at bp +36 and +43, where there are two sites for the ets family member PU.1. Mutation of these sites prevents PU.1 binding and reduces promoter activity by 75%. These results reinforce the importance of both PU.1 and C/EBP alpha in the expression of myeloid-specific genes and neutrophil development.
细胞因子在造血过程中对谱系定向和分化至关重要，它们通过结合特定受体发挥作用。受体表达受到严格调控，研究控制其表达的因素将有助于更好地理解决定谱系定向的事件。粒细胞集落刺激因子（G-CSF）受体仅在髓系细胞和胎盘中表达。我们在此表明，G-CSF受体转录起始位点在这些组织中的每一个中都是相同的。G-CSF受体启动子的一个1391 bp片段在髓系细胞系中具有活性且具有组织特异性。我们还发现了两个对G-CSF受体启动子活性很重要的区域。一个区域位于-49 bp处，含有一个GCAAT位点，该位点在髓系核提取物中特异性结合C/EBPα转录因子。该位点的突变会阻止C/EBPα结合，并使启动子活性降低60%。G-CSF受体启动子的另一个功能重要区域在5'非翻译区，位于+36和+43 bp处，这里有两个ets家族成员PU.1的结合位点。这些位点的突变会阻止PU.1结合，并使启动子活性降低75%。这些结果强化了PU.1和C/EBPα在髓系特异性基因表达和中性粒细胞发育中的重要性。
