No abstract

Drosophila melanogaster is one of the most extensively used genetic model organisms for studying LTR retrotransposons that are represented by various groups in its genome. However, the phenomenon of molecular domestication of LTR retrotransposons has been insufficiently studied in Drosophila, as well as in other invertebrates. The present work is devoted to studying the role of the domesticated gag gene, Gagr, in the Drosophila genome. The Gagr gene has been shown to be involved in the response to stress caused by exposure to ammonium persulfate, but not in the stress response to oligomycin A, zeomycin, and cadmium chloride. Ammonium persulfate tissue specifically activates the expression of Gagr in the tissues of the carcass, but not in the gut. We found that the Gagr gene promoter contains one binding motif for the transcription factor kayak, a component of the JNK signaling pathway, and two binding motifs for the transcription factor Stat92E, a component of the Jak-STAT signaling pathway. Remarkably, Gagr orthologs contain the second binding motif for Stat92E only in D. melanogaster, D. simulans and D. sechellia, whereas in D. yakuba and D. erecta, Gagr orthologs contain a single motif, and there are no binding sites for Stat92E in the promoters of Gagr orthologs in D. ananassae and in species outside the melanogaster group. The data obtained indicate the formation of the protective function of the Gagr gene during evolution.

Objective: to study the state of the genome in terms of the activity of retrotransposons and the gene encoding DNA methyltransferase I (DNMT1) as well as DNA damage in animals from the natural population of the bank vole (Clethrionomys glareolus) inhabiting the territory in the vicinity of the conserved landfill Salariyevo (municipal waste disposal site, Moscow) contaminated by dioxins in low concentrations. Methods: activity of retrotransposons ERV-L, B1 and L1 and the transcription level of the DNMT1 gene was assessed by real-time PCR. The DNA stability in liver and bone marrow cells was characterized by the Comet Assay method. The obtained characteristics of the genome (resistance, reactivity and damage) in response to the environmental stress factors were compared among groups of animals from the studied and conditionally control samples. Results: the effects of a decrease in the activity of retrotransposons of classes B1 and L1 and an increase in the level of expression of the DNMT1 gene were revealed in voles from the natural population living under conditions of long-lasting chronic exposure to low doses of dioxins. An increased level of DNA damage was detected in hepatocytes (on average, up to 56% of DNA in the comet's tail) with the additional effect of winter factors besides the chronic influence of low subtoxic doses of dioxins. Conclusions: suppression of the activity of retrotransposons and an increase in the expression of its epigenetic regulator (DNMT1) are considered to be a voles population adaptive strategy to long-lasting chronic exposure to dioxins contaminating the environment in low doses. Alterations in the genome reactivity and destabilization indicate the initiation of the primary mechanisms of the toxic process development. Thus, the produced and tested methodological base for this process study among environmentally exposed populations opens up some prospects for a threshold level establishing, and subsequently, verifying indicators for local assessment of the public health risk using biomonitoring methods.

Results of expression analysis of transcription of the flamenco locus that controls transposition of the mobile genetic element gypsy, RNA interference system genes ago3, zuc, aub, and HP1 heterochromatin protein family genes hp1a, hp1b, hp1c, hp1d (rhino), and hp1e in D. melanogaster SS strain mutant on the flamenco gene are presented. We show that the number of transcripts in the SS strain that are formed in the flamenco locus is unchanged in some freely chosen points, and this is different from the wild-type strain where a decreased number of transcripts is observed, which clearly is a result of processing of the flamenco locus primary transcript, a predecessor of piRNA. At the same time, expression of genes of the RNA interference system is not affected, but there is a reduced level of hp1d gene expression in ovary tissue. We suggest that the hp1d gene product is directly or indirectly involved in the flamenco locus primary transcript processing.