Hommura Fumihiro, Katabami Motoo, Leaner Virna D, Donninger Howard, Sumter Takita F, Resar Linda M S, Birrer Michael J
Cell and Cancer Biology Branch, National Cancer Institute, Rockville, MD, USA.
Mol Cancer Res. 2004 May;2(5):305-14.
The transcription complex activator protein-1 (AP-1) plays a role in a diverse number of cellular processes including proliferation, differentiation, and apoptosis. To identify AP-1-responsive target genes, we used a doxycycline-inducible c-Jun system in Rat1a cells. The HMG-I/Y chromatin binding protein was found to be up-regulated by c-Jun. Following induction of c-Jun expression, Rat1a cells under nonadherent growth conditions have sustained HMG-I/Y mRNA expression and 2-fold higher protein than uninduced cells. HMG-I/Y promoter reporter assays show that HMG-I/Y promoter activity increases in the presence of c-Jun expression, and gel mobility shift assays demonstrate that induced c-Jun binds to an AP-1 consensus site at position -1,091 in the HMG-I/Y promoter. Suppression of HMG-I/Y expression by its antisense sequence significantly reduces the ability of c-Jun-overexpressing Rat1a cells to grow in an anchorage-independent fashion. HMG-I/Y transforms Rat1a cells (although the colonies are smaller than that observed for the cells overexpressing c-Jun). Taken together, these results suggest that HMG-I/Y is a direct transcriptional target of c-Jun necessary for c-Jun-induced anchorage-independent growth in Rat1a cells.
转录复合物激活蛋白-1（AP-1）在包括增殖、分化和凋亡在内的多种细胞过程中发挥作用。为了鉴定AP-1反应性靶基因，我们在Rat1a细胞中使用了强力霉素诱导的c-Jun系统。发现HMG-I/Y染色质结合蛋白被c-Jun上调。在诱导c-Jun表达后，处于非贴壁生长条件下的Rat1a细胞具有持续的HMG-I/Y mRNA表达，且蛋白质水平比未诱导细胞高2倍。HMG-I/Y启动子报告基因检测表明，在c-Jun表达存在的情况下，HMG-I/Y启动子活性增加，凝胶迁移率变动分析表明，诱导的c-Jun与HMG-I/Y启动子中-1,091位置的AP-1共有位点结合。用其反义序列抑制HMG-I/Y表达可显著降低过表达c-Jun的Rat1a细胞以不依赖贴壁方式生长的能力。HMG-I/Y可使Rat1a细胞发生转化（尽管形成的集落比过表达c-Jun的细胞形成的集落小）。综上所述，这些结果表明HMG-I/Y是c-Jun的直接转录靶标，是c-Jun诱导Rat1a细胞不依赖贴壁生长所必需的。
