The SR Protein B52/SRp55 Is Required for DNA Topoisomerase I Recruitment to Chromatin, mRNA Release and Transcription Shutdown

DNA- and RNA-processing pathways are integrated and interconnected in the eukaryotic nucleus to allow efficient gene expression and to maintain genomic stability. The recruitment of DNA Topoisomerase I (Topo I), an enzyme controlling DNA supercoiling and acting as a specific kinase for the SR-protein family of splicing factors, to highly transcribed loci represents a mechanism by which transcription and processing can be coordinated and genomic instability avoided. Here we show that Drosophila Topo I associates with and phosphorylates the SR protein B52. Surprisingly, expression of a high-affinity binding site for B52 in transgenic flies restricted localization, not only of B52, but also of Topo I to this single transcription site, whereas B52 RNAi knockdown induced mis-localization of Topo I in the nucleolus. Impaired delivery of Topo I to a heat shock gene caused retention of the mRNA at its site of transcription and delayed gene deactivation after heat shock. Our data show that B52 delivers Topo I to RNA polymerase II-active chromatin loci and provide the first evidence that DNA topology and mRNA release can be coordinated to control gene expression

DNA damage by lipid peroxidation products: implications in cancer, inflammation and autoimmunity

Oxidative stress and lipid peroxidation (LPO) induced by inflammation, excess metal storage and excess caloric intake cause generalized DNA damage, producing genotoxic and mutagenic effects. The consequent deregulation of cell homeostasis is implicated in the pathogenesis of a number of malignancies and degenerative diseases. Reactive aldehydes produced by LPO, such as malondialdehyde, acrolein, crotonaldehyde and 4-hydroxy-2-nonenal, react with DNA bases, generating promutagenic exocyclic DNA adducts, which likely contribute to the mutagenic and carcinogenic effects associated with oxidative stress-induced LPO. However, reactive aldehydes, when added to tumor cells, can exert an anticancerous effect. They act, analogously to other chemotherapeutic drugs, by forming DNA adducts and, in this way, they drive the tumor cells toward apoptosis. The aldehyde-DNA adducts, which can be observed during inflammation, play an important role by inducing epigenetic changes which, in turn, can modulate the inflammatory process. The pathogenic role of the adducts formed by the products of LPO with biological macromolecules in the breaking of immunological tolerance to self antigens and in the development of autoimmunity has been supported by a wealth of evidence. The instrumental role of the adducts of reactive LPO products with self protein antigens in the sensitization of autoreactive cells to the respective unmodified proteins and in the intermolecular spreading of the autoimmune responses to aldehyde-modified and native DNA is well documented. In contrast, further investigation is required in order to establish whether the formation of adducts of LPO products with DNA might incite substantial immune responsivity and might be instrumental for the spreading of the immunological responses from aldehyde-modified DNA to native DNA and similarly modified, unmodified and/or structurally analogous self protein antigens, thus leading to autoimmunity

Use of Decommissioned Anti-Personnel Mines as Part of Developing Landmine-Alternatives

W artykule przedstawiono wyniki prac konstruktorskich i badawczych dotyczących opracowania środków alternatywnych dla min przeciwpiechotnych. Przedstawione urządzenia, wchodzące w skład Systemu Sterowanych Ładunków Wybuchowych, zbudowane zostały w oparciu o będące na wyposażeniu SZ RP miny przeciwpiechotne MON-100 i stanowią tani w produkcji oraz skuteczny środek rażenia siły żywej. Opracowany sprzęt spełnia wymagania, jakie stawia przed Polską Konwencja Ottawska oraz wymagania Norm Obronnych dotyczących bezpieczeństwa użytkowania.The paper presents results of the design and research works on developing alternative devices for landmines, including anti-personal ones. The devices described, which are elements of the Controlled Explosive Charges System, were built basing on the directional anti-personal mines – MON-100, which are being taken out of service with the Polish Army. The devices are economic to produce and effective on the battlefield against hostile forces. The devices developed compliant requirements of the Ottawa Treaty and Polish Defence Standards on safety of use

Activities of Topoisomerase I in Its Complex with SRSF1

Human DNA topoisomerase I (topo I) catalyzes DNA relaxation and phosphorylates SRSF1. Whereas the structure of topo I complexed with DNA has been resolved, the structure of topo I in the complex with SRSF1 and structural determinants of topo I activities in this complex are not known. The main obstacle to resolving the structure is a contribution of unfolded domains of topo I and SRSF1 in formation of the complex. To overcome this difficulty, we employed a three-step strategy: identifying the interaction regions, modeling the complex, and validating the model with biochemical methods. The binding sites in both topo I and SRSF1 are localized in the structured regions as well as in the unfolded domains. One observes cooperation between the binding sites in topo I but not in SRSF1. Our results indicate two features of the unfolded RS domain of SRSF1 containing phosphorylated residues that are critical for the kinase activity of topo I: its spatial arrangement relative to topo I and the organization of its sequence. The efficiency of phosphorylation of SRSF1 depends on the length and flexibility of the spacer between the two RRM domains that uniquely determine an arrangement of the RS domain relative to topo I. The spacer also influences inhibition of DNA nicking, a prerequisite for DNA relaxation. To be phosphorylated, the RS domain has to include a short sequence recognized by topo I. A lack of this sequence in the mutants of SRSF1 or its spatial inaccessibility in SRSF9 makes them inadequate as topo I/kinase substrates