Martinerie C, Chevalier G, Rauscher F J, Perbal B
Laboratoire d'Oncologie Virale et Moléculaire, Institut Curie, Orsay, France.
Oncogene. 1996 Apr 4;12(7):1479-92.
The nov gene encodes a putative Insulin-like-Growth Factor-Binding-Protein (IGFBP) of a novel type which is structurally related to a family of growth-factors likely to play a role in the control of cell proliferation. In the kidney, nov is expressed essentially at the embryonic stage and alterations of nov expression, relative to the normal kidney, have been detected in both avian nephroblastomas and human Wilms' tumors. The levels of human nov (novH) and WT1 mRNA in individual Wilms' tumors have been shown to be inversely correlated, suggesting that the expression of novH could be under the negative control of WT1. We have now established the nucleotide sequence of the 5' flanking region and identified two transcription start sites by RNase protection assays and primer extension. We report that in transient cotransfection experiments the transcription activity of novH promoter constructs was repressed by two isoforms of WT1 proteins (WT1 and WT1+KTS). Repression of the novH promoter required both intact zinc finger regions and the NH2 transcription repression domain of WT1. Inasmuch as the minimal region of novH promoter required to mediate WT1 repression in vivo failed to bine recombinant WT1 protein in in vitro footprinting assays this repression may be mediated by either (i) low affinity sites cooperative interactions or (ii) indirectly via protein-protein interactions with another factor(s). Furthermore, constitutive expression of wild type WT1 into 293 cells resulted in a decrease of endogenous NOVH protein levels, suggesting that novH may be a physiological target for WT1. The downregulation of novH expression by WT1 might represent a key element in normal and tumoral nephrogenesis.
nov基因编码一种新型的假定胰岛素样生长因子结合蛋白（IGFBP），其结构与可能在细胞增殖控制中起作用的一类生长因子相关。在肾脏中，nov主要在胚胎阶段表达，在禽类肾母细胞瘤和人类威尔姆斯瘤中均检测到相对于正常肾脏nov表达的改变。已显示单个威尔姆斯瘤中人类nov（novH）和WT1 mRNA的水平呈负相关，这表明novH的表达可能受WT1的负调控。我们现已确定了5'侧翼区域的核苷酸序列，并通过核糖核酸酶保护试验和引物延伸鉴定了两个转录起始位点。我们报告，在瞬时共转染实验中，novH启动子构建体的转录活性被WT1蛋白的两种同工型（WT1和WT1 + KTS）抑制。novH启动子的抑制需要WT1完整的锌指区域和NH2转录抑制结构域。由于在体内介导WT1抑制所需的novH启动子的最小区域在体外足迹试验中未能结合重组WT1蛋白，这种抑制可能由以下两种方式介导：（i）低亲和力位点的协同相互作用或（ii）通过与另一种因子的蛋白质 - 蛋白质相互作用间接介导。此外，野生型WT1在293细胞中的组成型表达导致内源性NOVH蛋白水平降低，这表明novH可能是WTi的生理靶点。WT1对novH表达的下调可能是正常和肿瘤性肾发生中的关键因素。
