Selenium Regulation of Classical Glutathione Peroxidase Expression Requires the 3′ Untranslated Region in Chinese Hamster Ovary Cells , ,

Abstract

Classical glutathione peroxidase (GPX) mRNA levels fall dramatically in selenium (Se)-deficient animals, but it is not known whether this mechanism is related to the mRNA 3' untranslated region (3'UTR) sequences that have been shown to direct Se incorporation. In this study, we used recombinant GPX constructs to investigate the role of the GPX 3'UTR in Se regulation of GPX mRNA levels in Chinese hamster ovary (CHO) cells. The CHO cells were transfected with GPX (pRc/GPX), GPX lacking the 3'UTR (pRc/Delta3'UTR) or the pRc/CMV vector alone, and GPX activity and GPX mRNA levels were determined in stable transfectants grown in low Se basal medium with a range of added Se concentrations. We identified two pRc/GPX transfectants with significantly elevated GPX activity levels compared with pRc/CMV transfectants. The elevated GPX expression did not dramatically shift the amount of Se that was sufficient for GPX activity to reach the Se-adequate plateau level (100 nmol/L added Se). As expected, GPX activity was not significantly different when pRc/Delta3'UTR transfectants were compared with pRc/CMV control transfectants. Among the wild type and transfected CHO cells, Se-deficient GPX activity levels averaged 35 +/- 5% of Se-adequate levels. Selenium-deficient levels of endogenous GPX mRNA as well as recombinant pRc/GPX mRNA averaged 54-58% of Se-adequate levels; 3-4 nmol/L added Se was sufficient for maximal GPX mRNA levels. In contrast, pRc/Delta3'UTR mRNA levels in the unsupplemented cells remained at Se-adequate levels and showed no distinct Se regulation. These studies demonstrate that the GPX 3'UTR is necessary for Se regulation of GPX mRNA levels in addition to its role in Se incorporation.

Dietary selenium regulation of glutathione peroxidase mRNA and other selenium-dependent parameters in male rats

“…Half-maximal GPX1 mRNA levels occurred before 0.05 μg Se/g diet whereas half-maximal GPX activity levels occurred at 0.07 μg Se/g diet. In other studies with rats 6,24 and with cultured cells 20 we have shown that GPX1 mRNA levels clearly reach the plateau breakpoint at a lower Se level than for GPX activity. In the present study, we needed an intermediate dietary treatment between 0.05 and 0.1 μg Se/g diet to show more conclusively that GPX1 mRNA levels reach the plateau breakpoint before GPX activity.…”

“…2,6,[14][15][16][17] Several studies have shown that GPX1 transcription is not affected by Se status, [17][18][19] indicating that Se status must regulate GPX1 mRNA stability. We have recently demonstrated that the GPX1 3' untranslated region (3'UTR) is necessary for GPX1 mRNA levels to decrease in Se-deficient cells, 20 suggesting that the GPX1 3'UTR may contain an Se-responsive element.…”

Genistein, a soy isoflavone, induces glutathione peroxidase in the human prostate cancer cell lines LNCaP and PC‐3

“…41 Dietary selenium stabilizes GPx mRNA 42 and the 3Ј untranslated region of the GPx gene plays an important role in GPx gene expression. 43 Enzyme activity of GPx is also upregulated by selenium in human cell lines. 44,45 There are only a few published studies on the in vitro effects of selenium on prostate cancer cell lines and most of them described an inhibitory effect of selenium on prostate cancer cells as an acute short-term effect.…”

Modeling and gene knockdown to assess the contribution of nonsense-mediated decay, premature termination, and selenocysteine insertion to the selenoprotein hierarchy

“…A recent study has provided some experimental support for this hypothesis (Seyedali and Berry 2014) and earlier work showed that during Se deficiency, GPX1 mRNA, but not GPX4 mRNA, was targeted by NMD (Weiss and Sunde 1997;Moriarty et al 1998). However, there is also evidence that susceptibility of NMD is not sufficient to explain the variability of selenoprotein mRNA responses to Se deficiency.…”