Institut für Vegetative Physiologie, Charité - Universitätsmedizin Berlin Berlin, Germany.
Front Mol Neurosci. 2011 Feb 7;4:1. doi: 10.3389/fnmol.2011.00001. eCollection 2011.
Human achaete-scute homolog-1 (hASH1), encoded by the human ASCL1 gene, belongs to the family of basic helix-loop-helix transcription factors. hASH1 and its mammalian homolog Mash1 are expressed in the central and peripheral nervous system during development, and promote early neuronal differentiation. Furthermore, hASH1 is involved in the specification of neuronal subtype identities. Misexpression of the transcription factor is correlated with a variety of tumors, including lung cancer and neuroendocrine tumors. To gain insights into the molecular mechanisms of hASH1 regulation, we screened for conditions causing changes in hASH1 gene expression rate. We found that treatment of human neuroblastoma-derived Kelly cells with phorbol 12-myristate 13-acetate (PMA) resulted in a fast, strong and long-lasting suppression of hASH1 synthesis. Reporter gene assays with constructs, in which the luciferase activity was controlled either by the ASCL1 promoter or by the hASH1 mRNA untranslated regions (UTRs), revealed a mainly UTR-dependent mechanism. The hASH1 promoter activity was decreased only after 48 h of PMA administration. Our data indicate that different mechanisms acting consecutively at the transcriptional and post-transcriptional level are responsible for hASH1 suppression after PMA treatment. We provide evidence that short term inhibition of hASH1 synthesis is attributed to hASH1 mRNA destabilization, which seems to depend mainly on protein kinase C activity. Under prolonged conditions (48 h), hASH1 suppression is mediated by decreased promoter activity and inhibition of mRNA translation.
人类achaete-scute 同源物-1（hASH1），由人类 ASCL1 基因编码，属于碱性螺旋-环-螺旋转录因子家族。hASH1 和其哺乳动物同源物 Mash1 在发育过程中表达于中枢和外周神经系统，促进早期神经元分化。此外，hASH1 参与神经元亚型身份的特化。转录因子的异常表达与多种肿瘤相关，包括肺癌和神经内分泌肿瘤。为了深入了解 hASH1 调节的分子机制，我们筛选了导致 hASH1 基因表达率变化的条件。我们发现，佛波醇 12-肉豆蔻酸 13-乙酸酯（PMA）处理人神经母细胞瘤衍生的 Kelly 细胞导致 hASH1 合成的快速、强烈和持久抑制。用构建体进行的报告基因分析，其中荧光素酶活性受 ASCL1 启动子或 hASH1 mRNA 非翻译区（UTR）控制，揭示了主要是 UTR 依赖性的机制。只有在 PMA 给药 48 小时后，hASH1 启动子活性才降低。我们的数据表明，在转录和转录后水平上连续作用的不同机制负责 PMA 处理后 hASH1 的抑制。我们提供的证据表明，hASH1 合成的短期抑制归因于 hASH1 mRNA 的不稳定性，这似乎主要依赖于蛋白激酶 C 活性。在延长的条件下（48 小时），hASH1 的抑制是通过降低启动子活性和抑制 mRNA 翻译介导的。
