Beauparlant P, Kwan I, Bitar R, Chou P, Koromilas A E, Sonenberg N, Hiscott J
Terry Fox Molecular Oncology Group, Lady Davis Institute for Medical Research, Jewish General Hospital, Montreal, Canada.
Oncogene. 1994 Nov;9(11):3189-97.
NF-kappa B transcription factors regulate the expression of a variety of genes involved in immune regulation and cell growth. In most cell types NF-kappa B proteins are localized in an inactive form in the cytoplasm coupled to the inhibitory I kappa B proteins. Viruses, cytokines, lipopolysaccharides and other stimulating agents promote the dissociation of the cytosolic NF-kappa B/I kappa B complexes, via phosphorylation and degradation of I kappa B, resulting in the translocation of DNA binding, NF-kappa B complexes to the nucleus. To further understand the association of I kappa B with cell growth regulation, the effect of ectopic expression of sense and antisense I kappa B genes was examined in NIH3T3 cells. Overexpression of I kappa B alpha antisense RNA but not I kappa B gamma antisense RNA decreased the steady state levels of I kappa B alpha protein, altered NF-kappa B DNA binding and gene activity and, most importantly, induced malignant transformation as measured by saturation density, growth in soft agar and tumorigenicity in nude mice. In contrast, overexpression of I kappa B alpha resulted in decreased saturation density, a flattened cellular morphology and decreased NF-kappa B dependent reporter gene activity. These results indicate that overexpression of an I kappa B alpha antisense RNA may disrupt the NF-kappa B/I kappa B autoregulatory loop, leading to cellular transformation. Our results raise the interesting possibility that I kappa B alpha represents a potential tumor suppressor activity.
核因子κB转录因子调控多种参与免疫调节和细胞生长的基因的表达。在大多数细胞类型中，核因子κB蛋白以无活性形式定位于细胞质中，并与抑制性IκB蛋白结合。病毒、细胞因子、脂多糖和其他刺激因子通过IκB的磷酸化和降解促进胞质内核因子κB/IκB复合物的解离，导致具有DNA结合活性的核因子κB复合物转位至细胞核。为了进一步了解IκB与细胞生长调节的关系，我们检测了正义和反义IκB基因在NIH3T3细胞中的异位表达效应。IκBα反义RNA而非IκBγ反义RNA的过表达降低了IκBα蛋白的稳态水平，改变了核因子κB的DNA结合活性和基因活性，最重要的是，通过饱和密度、软琼脂生长和裸鼠致瘤性检测发现其诱导了恶性转化。相反，IκBα的过表达导致饱和密度降低、细胞形态扁平以及核因子κB依赖性报告基因活性降低。这些结果表明，IκBα反义RNA的过表达可能破坏核因子κB/IκB自调节环，导致细胞转化。我们的结果提出了一个有趣的可能性，即IκBα代表一种潜在的肿瘤抑制活性。
