Analysis of Glucocorticoid Target Genes

为了确定负责介导糖皮质激素（GC）对白血病细胞的影响的基因，在GC敏感的人前B白血病697细胞在GC诱导的凋亡过程中的转录变化，使用寡核苷酸芯片监测。在检测的12，000个基因中，93个基因被诱导，28个基因被抑制，其中许多基因与信号转导、生长停滞和转录有关。这些基因包括SOCS1、SOCS2、FKBP5、DSCR1、p561ck和4种蛋白激酶磷酸酶。生长停滞相关基因编码p19 α和几个Myc抑制剂诱导响应GC处理。<INK4d>编码BTG1、BTG2和颗粒酶A（GZMA）的抗增殖或凋亡相关基因也被发现被GC转录上调。此外，调控基因编码的糖皮质激素受体（GR）和类固醇受体共激活因子-1建议自动调节的GC介导的信号通路。这些基因被上调，即使在存在蛋白质合成的抑制剂，放线菌酮，表明它们是直接的目标基因的GR。DSCR1据报道有四个亚型，其中每一个都有一个独特的第一外显子，E1至E4。在这些异构体中，与E1的一个被GC选择性上调。GZMA和FKBP 5在内含子1和内含子2中分别具有一簇推定的糖皮质激素反应元件（GRES），其被鉴定为负责对GC的反应。它们由一个完整的（A/T）G（A/T）（A/T）C（A/T）序列和两个不完整的（A/T）G（A/T）（A/T）C（A/T）序列组成，两个不完整的（A/T）G（A/T）（A/T）C（A/T）序列相隔1~4个核苷酸。然而，DSCR1在外显子1的上游或下游没有功能性GRE。这些研究可能导致基于这些GC靶基因的表达的GC在白血病和淋巴瘤中的改善的治疗用途。

To determine the genes responsible for mediating the effects of glucocorticoids (GCs) on leukemic cells, the transcriptional changes in GC-sensitive human pre-B leukemia 697 cells during GC-induced apoptosis were monitored using oligonucleotide microarrays. Of 12,000 genes examined for their response to GC, 93 genes were induced and 28 genes were repressed, many of which are known to be implicated in signal transduction, growth arrest and transcription. These included the signal transduction-related genes encoding SOCS1, SOCS2, FKBP5, DSCR1, p561ck and four protein kinase phosphatases. Growth arrest-related genes encoding p19^<INK4d> and several Myc inhibitors were induced in response to the GC treatment. Anti-proliferative- or apoptosis-related genes encoding BTG1, BTG2 and granzyme A (GZMA) were also found to be transcriptionally up-regulated by GC. In addition, the regulation of genes encoding the glucocorticoid receptor (GR) and steroid receptor coactivator-1 suggested autoregulation of a GC-mediated signaling pathway. These genes were upregulated by GC even in the presence of an inhibitor of protein synthesis, cycloheximide, indicating that they are direct target genes of GR. DSCR1 is reported to have four isoforms, each of which has a distinct first exon, E1 to E4. Among these isoforms, the one with E1 was selectively upregulated by GC. GZMA and FKBP5 have a cluster of putative glucocorticoid response elements (GREs) in intron 1 and intron 2, respectively, that was identified to be responsible for the response to GC. They were composed of one complete (A/T)G(A/T)(A/T)C(A/T) sequence surrounded by two incomplete (A/T)G(A/T)(A/T)C(A/T) sequence separated by one to four nucleotides. DSCR1, however, did not have a functional GRE upstream or downstream of exon 1. These studies may lead to improved therapeutic uses of GCs in leukemia and lymphoma based upon the expression of these GC target genes.