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We overexpressed duplex-specific nuclease (DSN) from Kamchatka crab in Escherichia coli cells and developed procedures for purification, renaturation, and activation of this protein. We demonstrated identity of the properties of the native and recombinant DSN. We also successfully applied the recombinant DSN for full-length cDNA library normalization.

A technique for the Selective Differential Display of RNAs containing Interspersed Repeats (SDDIR) has been elaborated. SDDIR involves two main steps: (1) selective amplification by RT-PCR of a subset of the total cellular RNA containing a certain type of repetitive element, and (2) side-by-side display of the amplicons derived from the tissues under comparison by means of gel electrophoresis in parallel lanes. The technique was used to compare the expression of transcripts containing LTR (Long Terminal Repeat) sequences derived from human endogenous retrovirus K (HERV-K) in testicular germ cell tumors and in corresponding normal tissue. SDDIR enabled us to obtain an overview of LTRs represented in the total transcribed fraction and to reveal differences in transcription patterns of the LTRs in normal and tumor tissues. An unexpectedly large number of LTRs was found to be transcribed, and the levels of many of the transcripts differed between normal and tumor tissues.

High levels of methylmercury accumulation in marine biota are a concern throughout the Arctic, where coastal ocean ecosystems received large riverine inputs of mercury (Hg) (40 Mg·y−1) and sediment (20 Tg·y−1) during the last decade, primarily from major Russian rivers. Hg concentrations in fish harvested from these rivers have declined since the late 20th century, but no temporal data on riverine Hg, which is often strongly associated with suspended sediments, were previously available. Here, we investigate temporal trends in Russian river particulate Hg (PHg) and total suspended solids (TSS) to better understand recent changes in the Arctic Hg cycle and its potential future trajectories. We used 1,300 measurements of Hg in TSS together with discharge observations made by Russian hydrochemistry and hydrology monitoring programs to examine changes in PHg and TSS concentrations and fluxes in eight major Russian rivers between ca. 1975 and 2010. Due to decreases in both PHg concentrations (micrograms per gram) and TSS loads, annual PHg export declined from 47 to 7 Mg·y−1 overall and up to 92% for individual rivers. Modeling of atmospheric Hg deposition together with published inventories on reservoir establishment and industrial Hg release point to decreased pollution and sedimentation within reservoirs as predominant drivers of declining PHg export. We estimate that Russian rivers were the primary source of Hg to the Arctic Ocean in the mid to late 20th century.