Association of castration-dependent early induction of c-myc expression with a cell proliferation of the ventral prostate gland in rat

Differential regulation of vimentin mRNA by 12-O-tetradecanoylphorbol 13-acetate and all-trans-retinoic acid correlates with motility of Hep 3B human hepatocellular carcinoma cells

Vimentin is a growth-related gene and often expressed when epithelial cells are stimulated to proliferate by growth factors. In cancer, vimentin expression is associated with a dedifferentiated malignant phenotype, increased motility, invasive ability and poor prognosis. We studied the regulation of vimentin mRNA and multistep invasion processes following treatment of 12-O-tetradecanoylphorbol 13-acetate (TPA) and all-trans-retinoic acid (RA) in Hep 3B hepatocellular carcinoma cells. TPA showed marked induction of vimentin mRNA, while RA decreased the mRNA level. TPA or RA did not affect cell proliferation, cell-matrix protein adhesion, and matrix metalloproteinases and urokinase plasminogen activator activities. In vitro invasion ability was significantly increased or decreased with TPA or RA treatment, paralleled to the in vitro motile activity, respectively. These findings suggest that TPA and RA could modulate the invasive potential of Hep 3B cells by altering cellular motility related to differential regulation of vimentin mRNA.

ATF is important to late S phase-dependent regulation of DNA topoisomerase IIalpha gene expression in HeLa cells

DNA topoisomerase IIalpha (Topo IIalpha) is regulated in late S phase-dependent manner. To identify late S phase-dependent cis-acting elements of Topo IIalpha gene, we have investigated the synchronized HeLa cells with chloramphenicol acetyltransferase and DNase I footprinting assays. The level of Topo IIalpha mRNA increased after release from aphidicolin block and reached a maximum in 8h (late S phase) in HeLa cells, and Topo II unknotting activity was also in parallel with the level of Topo IIalpha mRNA. The late S phase-regulatory element was found to be located in the region containing ATF-binding element between -290 and -90bp and the region was required for a maximal stimulation during late S phase. DNase I footprinting assay showed that ATF-binding element and novel cis-acting element (Topo IIalpha-specific sequence) were the principal protein-binding sites and the proteins interacting with these elements were induced during late S phase. One DNA-protein complex was formed by DNA mobility shift assay when ATF-binding site was incubated with nuclear extract prepared from late S phase cells, but no protein bound in non-S phase cells. Taken together, these results suggest that ATF may be essential transacting factor for maximal expression of Topo IIalpha gene during late S phase in HeLa cells.

Modification of octamer binding transcriptional factor is related to H2B histone gene repression during dimethyl sulfoxide-dependent differentiation of HL-60 cells

Transcriptional regulation of H2B histone gene during dimethyl sulfoxide (DMSO)-dependent differentiation of HL-60 cells has been investigated using DNase I footprinting and DNA mobility shift assay. The level of histone H2B mRNA showed a slight decline at 2 days and hardly detectable at 4 days after DMSO treatment. H2B histone mRNA was repressed in proportion to the concentration of DMSO. In DNase I footprinting analysis, one nuclear factor (octamer binding transcription factor, OTF) bound at -42 bp (octamer motif, ATTTGCAT) in undifferentiated HL-60 cells. The binding pattern of OTF was unchanged during DMSO-dependent differentiation. One protein complex (OTF) was detected by DNA mobility shift assay in undifferentiated HL-60 cells. The mobility of OTF was partially retarded during DMSO-dependent differentiation and the retardant OTF was not newly synthesized protein. These results suggest that the posttranslational modification of OTF may be responsible for the repression of H2B histone gene during DMSO-dependent differentiation of HL-60 cells.