Molecular responses to genotoxic stress, such as ionizing radiation, are intricately complex and involve hundreds of genes. Whether targeted overexpression of an endogenous gene can enhance resistance to ionizing radiation remains to be explored. In the present study we take an advantage of the CRISPR/dCas9 technology to moderately overexpress the RPA1 gene that encodes a key functional subunit of the replication protein A (RPA). RPA is a highly conserved heterotrimeric single-stranded DNA-binding protein complex involved in DNA replication, recombination, and repair. Dysfunction of RPA1 is detrimental for cells and organisms and can lead to diminished resistance to many stress factors. We demonstrate that HEK293T cells overexpressing RPA1 exhibit enhanced resistance to cell killing by gamma-radiation. Using the alkali comet assay, we show a remarkable acceleration of DNA breaks rejoining after gammairradiation in RPA1 overexpressing cells. However, the spontaneous rate of DNA damage was also higher in the presence of RPA1 overexpression, suggesting alterations in the processing of replication errors due to elevated activity of the RPA protein. Additionally, the analysis of the distributions of cells with different levels of DNA damage showed a link between the RPA1 overexpression and the kinetics of DNA repair within differentially damaged cell subpopulations. Our results provide knew knowledge on DNA damage stress responses and indicate that the concept of enhancing radioresistance by targeted alteration of the expression of a single gene is feasible, however undesired consequences should be considered and evaluated.

The present comprehensive study aimed to estimate the aftermath of oil contamination and the efficacy of removing the upper level of polluted soil under the conditions of the extreme northern taiga of northeastern European Russia. Soil samples from three sites were studied. Two sites were contaminated with the contents of a nearby sludge collector five years prior to sampling. The highly contaminated upper soil level was removed from one of them. The other was left for self-restoration. A chemical analysis of the soils was conducted, and changes in the composition of the soil zoocoenosis and bacterial and fungal microbiota were investigated. At both contaminated sites, a decrease in the abundance and taxonomic diversity of indicator groups of soil fauna, oribatid mites and collembolans compared to the background site were found. The pioneer eurytopic species Oppiella nova, Proisotoma minima and Xenyllodes armatus formed the basis of the microarthropod populations in the contaminated soil. A complete change in the composition of dominant taxonomic units was observed in the microbiota, both the bacterial and fungal communities. There was an increase in the proportion of representatives of Proteobacteria and Actinobacteria in polluted soils compared to the background community. Hydrocarbon-degrading bacteria—Alcanivorax, Rhodanobacter ginsengisoli, Acidobacterium capsulatum, and Acidocella—and fungi—Amorphotheca resinae abundances greatly increased in oil-contaminated soil. Moreover, among both bacteria and fungi, a sharp increase in the abundance of uncultivated organisms that deserve additional attention as potential oil degraders or organisms with a high resistance to oil contamination were observed. The removal of the upper soil level was partly effective in terms of decreasing the oil product concentration (from approximately 21 to 2.6 g/kg of soil) and preventing a decrease in taxonomic richness but did not prevent alterations in the composition of the microbiota or zoocoenosis.

Reactive oxygen species (ROS) are normal products of a number of biochemical reactions and are important signaling molecules. However, at the same time, they are toxic to cells and have to be strictly regulated by their antioxidant systems. The etiology and pathogenesis of many diseases are associated with increased ROS levels, and many external stress factors directly or indirectly cause oxidative stress in cells. Within this context, the overexpression of genes encoding the proteins in antioxidant systems seems to have become a viable approach to decrease the oxidative stress caused by pathological conditions and to increase cellular stress resistance. However, such manipulations unavoidably lead to side effects, the most dangerous of which is an increased probability of healthy tissue malignization or increased tumor aggression. The aims of the present review were to collect and systematize the results of studies devoted to the effects resulting from the overexpression of antioxidant system genes on stress resistance and carcinogenesis in vitro and in vivo. In most cases, the overexpression of these genes was shown to increase cell and organism resistances to factors that induce oxidative and genotoxic stress but to also have different effects on cancer initiation and promotion. The last fact greatly limits perspectives of such manipulations in practice. The overexpression of GPX3 and SOD3 encoding secreted proteins seems to be the “safest” among the genes that can increase cell resistance to oxidative stress. High efficiency and safety potential can also be found for SOD2 overexpression in combinations with GPX1 or CAT and for similar combinations that lead to no significant changes in H2O2 levels. Accumulation, systematization, and the integral analysis of data on antioxidant gene overexpression effects can help to develop approaches for practical uses in biomedical and agricultural areas. Additionally, a number of factors such as genetic and functional context, cell and tissue type, differences in the function of transcripts of one and the same gene, regulatory interactions, and additional functions should be taken into account.

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Синтезирован ряд новых порфиринатов переходных металлов на основе производных хлорофилла а с фрагментами диэтиленгликоля на периферии хлоринового макроцикла и изучено влияние положения фрагмента диэтиленгликоля, наличия и природы координированного катиона металла (Cu 2+ , Zn 2+ , Ni 2+) на цитотоксическую активность производных хлорофилла а по отношению к клеткам линии HeLa. Основные тенденции влияния металла на цитотоксические свойства заключаются в том, что внедрение катиона цинка существенно повышает цитотоксичность при переходе от низкотоксичных безметальных хлоринов к соответствующим комплексам и слабо влияет в случае относительно токсичных хлоринов, а внедрение катиона никеля и меди практически не изменяет или несколько снижает цитотоксический эффект. Исключение составляет диэтиленгликолевый эфир пирофеофорбида а, который значительно менее цитотоксичен, чем соответствующий порфиринат меди. Влияние внедрения фрагмента диэтиленгликоля в случае порфиринатов меди заключается в повышении цитотоксичности, а в случае порфиринатов цинка и никеля цитотоксические свойства в большинстве случаев изменяются слабо. Наибольшей цитотоксической активностью обладают комплексы на основе производных хлорофилла а без экзоцикла, а так же порфиринат цинка на основе диэтиленгликолевого эфира пирофеофорбида а. Среди них наибольшей цитотоксичностью обладает порфиринат никеля на основе 13-метиламидного производного хлорина е 6 с фрагментом диэтиленгликоля в положении 17 макроцикла. Все перечисленные производные представляют интерес с точки зрения более подробного изучения в качестве потенциальных темновых противоопухолевых цитотоксических агентов. Ключевые слова: Порфиринаты переходных металлов, производные хлорина е 6 , производные пирофеофорбида а, метилфеофорбид а, диэтиленгликоль, фотонезависимая цитотоксическая активность, in vitro.