Mackler S A, Homan Y X, Korutla L, Conti A C, Blendy J A
Department of Medicine, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6084, USA.
Neuroscience. 2003;121(2):355-61. doi: 10.1016/s0306-4522(03)00376-2.
NAC1 cDNA was identified as a novel transcript induced in the nucleus accumbens from rats chronically treated with cocaine. NAC1 is a member of the Bric-a-brac Tramtrac Broad complex/Pox virus and Zinc finger family of transcription factors and has been shown by overexpression studies to prevent the development of behavioral sensitization resulting from repeated cocaine treatment. This paper reports the cloning and characterization of the corresponding gene. The mouse Nac1 gene consist of six exons, with exon 2 containing an alternative splice donor, providing a molecular explanation of the splice variants observed in mouse and rat. Transcripts of Nac1 were ubiquitously detected in different mouse tissues with prominent expression in the brain. The mouse Nac1 gene was localized to chromosome 8, suggesting a highly plausible candidate gene to explain differences in cocaine-induced behaviors between C57BL6/J and DBA/2J mice that had previously been mapped to the area. In addition, a functional AP1 binding site has been identified in an intron 1 enhancer of the Nac1 gene that plays an essential role in the activation of the gene in differentiation of neuroblastoma cells. Co-transfection with c-jun and c-fos expression plasmids, which encode the two subunits of AP1, activated the wild type Nac1 intron 1 enhancer two-fold over basal, nearly at the level of NAC1 enhancer activity seen in differentiated N2A cells. Mutation of the AP1 site completely abrogated all activation of the NAC1 enhancer in differentiated N2A cells. Activation of immediate early genes such as c-fos and c-jun following chronic drug treatments has been well characterized. The present data describe one potential regulatory cascade involving these transcription factors and activation of NAC1. Identification of drug induced alterations in gene expression is key to understanding the types of molecular adaptations underlying addiction.
NAC1 cDNA被鉴定为一种在长期接受可卡因治疗的大鼠伏隔核中诱导产生的新型转录本。NAC1是转录因子Bric-a-brac Tramtrac Broad complex/痘病毒和锌指家族的成员，过表达研究表明它可防止重复给予可卡因导致的行为敏化的发展。本文报道了相应基因的克隆和特性分析。小鼠Nac1基因由六个外显子组成，外显子2包含一个可变剪接受体，这为在小鼠和大鼠中观察到的剪接变体提供了分子解释。在不同小鼠组织中均普遍检测到Nac1的转录本，在脑中表达尤为显著。小鼠Nac1基因定位于8号染色体，这表明它是一个非常有可能的候选基因，可用于解释先前已定位到该区域的C57BL6/J和DBA/2J小鼠在可卡因诱导行为上的差异。此外，在Nac1基因的内含子1增强子中鉴定出一个功能性AP1结合位点，该位点在神经母细胞瘤细胞分化过程中基因的激活中起关键作用。与编码AP1两个亚基的c-jun和c-fos表达质粒共转染，可使野生型Nac1内含子1增强子的活性比基础水平提高两倍，几乎达到分化的N2A细胞中NAC1增强子活性的水平。AP1位点的突变完全消除了分化的N2A细胞中NAC1增强子的所有激活。长期药物治疗后立即早期基因如c-fos和c-jun的激活已得到充分表征。目前的数据描述了一个涉及这些转录因子和NAC1激活的潜在调控级联。鉴定药物诱导的基因表达变化是理解成瘾背后分子适应类型的关键。
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