[en] In the process of identifying genes that are differentially regulated in cells exposed to ultraviolet radiation (UV), we identified a transcript that was repressed following the exposure of cells to a combination of UV and salicylate, a known inhibitor of NF-kappaB. Sequencing this band determined that it has identify to lactate dehydrogenase, and Northern blots confirmed the initial expression pattern. Analysis of the sequence of the LDH 5' region established the presence of NF-kappaB, Sp1, and two Ap-2 elements; two partial AP- 1; one partial RE, and two halves of E-UV elements were also found. Electromobility shift assays were then performed for the AP-1, NF- kappaB, and E-UV elements. These experiments revealed that binding to NF-kappaB was induced by UV but repressed with salicylic acid; UV did not affect AP-1 binding, but salicylic acid inhibited it alone or following UV exposure; and E-UV binding was repressed by UV, and salicylic acid had little effect. Since the binding of no single element correlated with the expression pattern of LDH, it is likely that multiple elements govern UV/salicylate-mediated expression

[en] We examined the modulation in expression of genes encoding three cytoskeletal elements (beta-actin, gamma-actin, and alpha-tubulin) in Syrian hamster embryo (SHE) cells following exposure to ionizing radiations. Early-passage SHE cells were irradiated in plateau phase with various low doses (12-200 cGy) of neutrons, gamma-rays, or x-rays. RNA samples were prepared from cells at different times postexposure and were analyzed for levels of specific transcripts by northern blots. The results revealed that alpha-tubulin was induced by both high-linear energy of transfer (LET) (neutrons) and low-LET (gamma-rays and x-rays) radiations with similar kinetics. The peak in alpha-tubulin mRNA accumulation occurred between 1 and 3 h postexposure; for gamma-actin mRNA, accumulation was similarly induced. For both gamma-actin and alpha-tubulin, the higher the dose during the first hour postexposure (up to 200 cGy gamma-rays), the greater the level of mRNA induction. In contrast, mRNA specific for beta-actin showed decreased accumulation during the first hour following radiation exposure, and remained low up to 3 h postexposure. These results document the differential modulation of genes specific for cytoskeletal elements following radiation exposure. In addition, they demonstrate a decrease in the ratio of beta-actin:gamma-actin mRNA within the first 3 h following gamma-ray exposure. These changes in mRNA accumulation are similar to those reported in some transformed cell lines and in cells treated with tumor promoters, which suggests a role for changes in actin- and tubulin-mRNA expression in radiation-mediated transformation

[en] Members of the protein kinase C (PKC) gene family have been shown to play an important role in tumor promotion and regulation of cell growth. Experiments were designed to examine the effects of different qualities of ionizing radiation administered at a variety of doses and dose rates on the expression of PKC-specific mRNA in confluent Syrian hamster embryo cells. The results of these experiments showed that low-linear energy of transfer (LET) radiations (such as X-rays and gamma-rays) can induce increased expression of PKC mRNA within 1 h after radiation exposure. Levels of expression of PKC mRNA were increased 4- to 6-fold over unirradiated controls. Dose effects were evident, with increased accumulation of PKC mRNA at higher doses (ranging from 6 to 200 cGy). Induction of PKC mRNA occurred at a time when total cellular transcription was reduced following irradiation. Similar exposure of the cells to fission spectrum JANUS neutrons, however, had little effect on PKC mRNA expression. Modest induction (2-fold compared to untreated cells) occurred when irradiations were at very low dose rates (0.5 cGy/min). These results suggest that induction of PKC mRNA may be a step in the transformation process caused by ionizing radiation. In addition, they demonstrate that different qualities of radiation may regulate PKC differently