Disruption of I kappa B alpha regulation by antisense RNA expression leads to malignant transformation.
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.
Beauparlant
P
P
Terry Fox Molecular Oncology Group, Lady Davis Institute for Medical Research, Jewish General Hospital, Montreal, Canada.
Kwan
I
I
Bitar
R
R
Chou
P
P
Koromilas
A E
AE
Sonenberg
N
N
Hiscott
J
J
D016475:3T3 Cells; D000818:Animals; D001483:Base Sequence; D002471:Cell Transformation, Neoplastic; D002999:Clone Cells / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics*; D015870:Gene Expression; D006801:Humans; D020672:I-kappa B Proteins; D051379:Mice; D008819:Mice, Nude; D008969:Molecular Sequence Data; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000502:physiology*; D052002:NF-kappa B p50 Subunit; D009838:Oligodeoxyribonucleotides; D011485:Protein Binding; D016372:RNA, Antisense / Q000096:biosynthesis* / Q000235:genetics; D014157:Transcription Factors / Q000235:genetics
D004268:DNA-Binding Proteins; D020672:I-kappa B Proteins; D016328:NF-kappa B; D052002:NF-kappa B p50 Subunit; C489548:NFKB1 protein, human; C000606204:NFKBIA protein, human; C000606205:Nfkbia protein, mouse; D009838:Oligodeoxyribonucleotides; D016372:RNA, Antisense; D014157:Transcription Factors; D000072000:NF-KappaB Inhibitor alpha; C073701:Nfkb1 protein, mouse