Inhibition of messenger RNA accumulation but not translation in ultraviolet irradiated hepatoma cells
ABSTRACT Irradiation by ultraviolet light at doses between 30 and 90 ergs/mm2 increasingly inhibited the hydrocortisone but not the insulin induction of tyrosine aminotransferase activity in Reuber (H35) hepatoma cells in culture. Incorporation of lecuine into cellular protein was only slightly inhibited in this dose range. Incorporation of uridine into RNA in the presence of low doses of actinomycin D (0.1 μg/ml) was increasingly inhibited by ultraviolet irradiation. Since cellular uptake of uridine into the acid soluble pool was not inhibited by ultraviolet irradiation, the inhibition of RNA labeling suggests inhibition of synthesis of heterogenous nuclear RNA by low doses of ultraviolet irradiation. “Unscheduled” DNA synthesis was initially stimulated 2 fold by 30 ergs/mm2 irradiation and returned to control levels in 8 hours. Thus, ultraviolet irradiation in the low dose range causes DNA repair synthesis, inhibits transcription and apparently tyrosine aminotransferase messenger RNA accumulation while pre-existing cytoplasmic messenger appears not to be inactivated nor its translation inhibited.
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ABSTRACT: —Germicidal ultraviolet light (UVC. 8–10 J/m2) induces ornithine decarboxylase (ODC) in mouse epidermal cells in vitro in a biphasic manner with maxima of 2–3 fold induction at 4–6 h and of 10–20 fold induction at 15–18 h after irradiation. At this dose of UVC overall protein synthesis is inhibited by 10–30% and RNA synthesis by 40–50%. Induction of both ODC peaks is prevented by actinomycin D or cycloheximide. Similar culture factors appear to influence the extent of ODC induction by UVC and by the tumor promoter, 12-O-tetradecanoyl phorbol-13-acetate (TPA), since the ratio of peak activities is approximately constant at 2, whereas absolute values vary considerably between experiments. If cells are irradiated with UVC and then exposed to TPA, the effects are additive at 10 J/m2, less than additive at higher and enhanced at lower doses of UVC.Photochemistry and Photobiology 09/1980; 32(2):177-81. · 2.29 Impact Factor
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ABSTRACT: Ultraviolet irradiation mapping techniques have previously been used to study the organization of eucaryotic gene classes and transcription units. We used the same method to probe some regulatory phenomena observed in the induction of plasminogen activator (PA) biosynthesis: PA synthesis in chicken embryo fibroblasts is induced by tumor-promoting phorbol esters and by retinoic acid; furthermore, PA induction by phorbol esters is synergistic with transformation, being 10- to 20-fold greater in virus-transformed cells than in normal cells. We found that the ultraviolet irradiation inactivation cross sections for PA induction by phorbol esters and by retinoate differed significantly, suggesting that these agents induce PA biosynthesis by different mechanisms. On the other hand, the ultraviolet irradiation sensitivity of phorbol ester induction in normal chicken embryo fibroblasts was the same as in transformed cells, indicating that the synergism of transformation and phorbol esters is probably not due to different pathways of PA induction.Molecular and Cellular Biology 11/1981; 1(10):884-90. · 5.37 Impact Factor
- Quarterly Reviews of Biophysics 09/1981; 14(3):381-432. · 11.88 Impact Factor