Multiple promoter elements govern expression of the human ornithine decarboxylase gene in colon carcinoma cells

Abstract

Overexpression of the ornithine decarboxylase (ODC) gene may be important to the development and maintenance of colonic neoplasms, as well as tumors in general. In this study, we examined the promoter elements governing constitutive expression of the human ODC gene in HCT 116 human colon carcinoma cells and, for comparison, K562 human erythro-leukemia cells. It was determined by functional analysis that the promoter elements responsible reside within the 378 bp immediately upstream from the transcription start site. Within this sequence, there are at least three regions that modulate the efficiency of the ODC promoter cooperatively. Both DNA bandshift and footprint assays demonstrated all three regions to be rich in sites that bind to nuclear proteins isolated from HCT 116 and K562 cells; the protein binding pattern of non-transformed, diploid fibroblasts was found to be much less complex. Several of the protein binding sequences have little or no homology to common regulatory elements. We suggest that the constitutive activity of the ODC gene in HCT 116 colon carcinoma cells, and perhaps transformed cells in general, involves a complex interaction of multiple regulatory sequences and their associated nuclear proteins. Finally, the saturation of the promoter in these transformed cell lines suggests that high levels of protein binding in the ODC promoter may contribute to elevated constitutive expression of this gene.

eIF4E – from translation to transformation

“…Polyamines are essential for growth, differentiation, survival and mediate cellular transformation (reviewed in Shantz and Pegg, 1999;Schipper and Verhofstad, 2002;Hillary and Pegg, 2003). Overexpression of ODC transforms NIH 3T3 cells (Moshier et al, 1993;Auvinen et al, 1997). Transgenic expression of polyamine biosynthetic enzymes, such as ODC and S-adenosylmethionine decarboxylase in mice, causes skin cancer (reviewed in Pegg et al, 2003).…”

Mechanisms of apoptosis by c-Myc

“…How it impacts apoptosis is unclear, although one possibility is that excess polyamine catabolism generates reactive oxygen species (ROS) which promote mitochondriadependent apoptosis (Packham and Cleveland, 1995). ODC has overlapping roles in death and proliferation (Auvinen et al, 1992;Moshier et al, 1993;Packham and Cleveland, 1994;Shantz and Pegg, 1994).…”

Overexpression of antizyme-inhibitor in NIH3T3 fibroblasts provides growth advantage through neutralization of antizyme functions

“…Inhibition of ODC activity interferes with cellular transformation induced by proto-oncogenes (Auvinen et al, 1992;Holtta et al, 1993). In some cases, ODC overexpression is sufficient to induce cellular transformation (Auvinen et al, 1992;Moshier et al, 1993;Shantz and Pegg, 1994;Clifford et al, 1995), and spontaneous skin tumors in nude mice (Megosh et al, 1995). Recently, ODC was found to be an important downstream mediator of Myc-and APCdependent transformation pathways (Gerner and Meyskens, 2004;Nilsson et al, 2005).…”