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: 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. DOI:10.1128/MCB.1.10.884 · 5.04 Impact Factor
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ABSTRACT: The effects of cellular differentiation on the repair of DNA damage induced by uv radiation were investigated in the murine 3T3-T proadipocyte cell culture system. Upon exposure to human plasma, actively cycling 3T3-T cells (stem cells) undergo growth arrest, which is followed by terminal differentiation into lipid-laden adipocytes. In response to uv irradiation, the level of unscheduled DNA synthesis is significantly lower in adipocytes as compared to stem cells. The alkaline elution assay was used to monitor the appearance of repair-induced strand breaks in 3T3-T cells after uv irradiation. DNA strand breaks were detected in stem cells by 4 min post-uv with essentially no further increase after 8 min. When terminally differentiated adipocytes were irradiated and allowed to repair, however, more strand breaks were present at 4 min and, in marked contrast to stem cells, continued to accumulate in adipocytes for at least 16 min post-uv. Inhibition of repair-replication with hydroxyurea and cytosine arabinoside significantly increased accumulation of repair-induced strand breaks in stem cells, yet had little effect on this accumulation in adipocytes. For stem cells and adipocytes, incision activity was linear out to at least 10 Jm-2 without saturation. These data suggested that 3T3-T cell differentiation is accompanied by a defect in some postincision process of the excision-repair pathway.Radiation Research 12/1988; 116(2):217-27. DOI:10.2307/3577459 · 2.45 Impact Factor
Cancer Research 09/1978; 38(8):2533-8. · 9.28 Impact Factor