Date of Award
Doctor of Philosophy
Biochemistry, Biophysics and Molecular Biology
The production of the human chorionic gonadotropin alpha subunit and placental alkaline phosphatase (PAP) activity varied among different HeLa cell lines with regard to both constitutive and butyrate (Btr) induced expression. No correlation was observed between the extent of Btr induction and the constitutive level of synthesis for a given cell line. Moreover, Bts did not produce similar increases of both PAP and alpha, suggesting that the expression of these two genes is not coordinately regulated. Analysis of the subunits by column chromatography suggests that the difference in production rates for the cell lines is not due to differences in the size and carbohydrate structure of their protein products;Inhibitors of cell growth such as Btr, thymidine, bromodeoxyuridine, and iododeoxyuridine induced the synthesis of alpha and PAP. Dose response curves demonstrate that PAP is increased by lower concentrations of inducer than is alpha. The induction of both alpha and PAP was inhibited by 2 nM deoxycytidine (dCyd). Induction of PAP by Btr was more sensitive to dCyd inhibition than was the induction of alpha. This antagonism between Btr and dCyd does not appear to result from an inhibition of Btr uptake, a general cytotoxic effect of dCyd, the presence of a soluble inhibitor of PAP activity, or a reversal of the inhibition of DNA synthesis. Inhibition of Pap induction by dCyd was not observed in cells preincubated with Btr for 11 to 24 h before the addition of dCyd, indicating the dCyd interfered with an early event of Btr induction;The combination of Btr with other inducers was synergistic with respect to the induction of HeLa-(alpha) but not of PAP. Synergism was most prominent with 3 mM Btr and 1 mM theophylline, and it was specific for theophylline (xanthine, caffeine, and theobromine were not effective). This synergism did not appear to be mediated by cAMP. All of the xanthine compounds inhibited the butyrate induction of PAP. Although the mechanism(s) is not understood, these data suggest that nucleosides or their derivatives play a role in gene expression. Analysis of cytoplasmic dot hybridization data suggest that the primary effect of these various effectors is to increase (alpha)-mRNA.
Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/
Richard Neil Tamura
Tamura, Richard Neil, "The effect of nucleosides on the expression of the glycoprotein hormone alpha subunit and placental alkaline phosphatase in HeLa cells " (1984). Retrospective Theses and Dissertations. 8221.