Filmore R A, Dean D A, Zimmer W E
Department of Cell Biology and Neuroscience, University of South Alabama, Mobile, AL 36688, USA.
Gene Expr. 2002;10(5-6):201-11. doi: 10.3727/000000002783992424.
Nkx 3.1 is an evolutionarily conserved vertebrate homolog of the Drosophila Nk-3 homeodomain gene bagpipe that is expressed by a variety of cells during early mammalian development and has been shown to be a critical factor for prostate development and function. Previous studies utilizing a heterologous cell transfection strategy from our laboratory identified the smooth muscle gamma-actin (SMGA) gene as a novel molecular target of Nkx 3.1 regulatory activity. In the studies presented here, SMGA gene activity and regulation were evaluated in normal and cancerous prostate epithelial cells. SMGA transcripts were demonstrated in prostate epithelia and SMGA mRNA levels were increased in androgen-responsive LNCaP cancer and normal prostate epithelial cells. SMGA gene transcriptional activity was androgen responsive in these cells and required a segment of the human SMGA promoter containing NKE and SRF (serum response factor) binding elements. This region of the human SMGA proximal promoter is well conserved across species and is synergistically activated by coexpression of Nkx 3.1 and SRF in heterologous CV-1 cells. SMGA transcription was not responsive to steroid in PC-3 prostate epithelial cancer cells, which do not express Nkx 3.1. However, SMGA transcription was influenced by expression of androgen receptor in these cells, a situation that allows the androgen-dependent expression of Nkx 3.1. Furthermore, SMGA gene activity was influenced by direct Nkx 3.1 expression in the PC-3 cells. Thus, SMGA gene activity in prostate epithelia is due, in part, to the androgen-dependent expression of Nkx 3.1. As such, our studies provide the initial description of Nkx 3.1 target gene regulatory activity in the prostate.
Nkx 3.1是果蝇Nk-3同源异型结构域基因bagpipe在进化上保守的脊椎动物同源物，在哺乳动物早期发育过程中由多种细胞表达，并且已被证明是前列腺发育和功能的关键因素。我们实验室先前利用异源细胞转染策略的研究确定平滑肌γ-肌动蛋白（SMGA）基因是Nkx 3.1调控活性的新分子靶点。在本文介绍的研究中，对正常和癌性前列腺上皮细胞中的SMGA基因活性和调控进行了评估。在前列腺上皮中证实了SMGA转录本，并且在雄激素反应性LNCaP癌和正常前列腺上皮细胞中SMGA mRNA水平升高。SMGA基因转录活性在这些细胞中对雄激素有反应，并且需要一段包含NKE和血清反应因子（SRF）结合元件的人SMGA启动子。人SMGA近端启动子的这一区域在物种间高度保守，并且在异源CV-1细胞中通过Nkx 3.1和SRF的共表达被协同激活。在不表达Nkx 3.1的PC-3前列腺上皮癌细胞中，SMGA转录对类固醇无反应。然而，SMGA转录受这些细胞中雄激素受体表达的影响，这种情况允许Nkx 3.1的雄激素依赖性表达。此外，SMGA基因活性受PC-3细胞中Nkx 3.1直接表达的影响。因此，前列腺上皮中的SMGA基因活性部分归因于Nkx 3.1的雄激素依赖性表达。因此，我们的研究首次描述了Nkx 3.1靶基因在前列腺中的调控活性。
