The role of dead standing biomass of Calamagrostis epigejos in nutrient turnover during spontaneous succession.

Here we explore the idea that keeping dead standing (marcescent) biomass plants can reduce its nutrient (N, P) content. Later after biomass falling to ground this may result in substantial changes in nutrient turnover with consequences for plant competitive interactions. To explore the effects standing dead biomass we used Calamagrostis epigejos as a model species. It is a common expansive grass, which after senescence retain a large proportion of the plant remains as dead standing biomass. We determined the biomass, N and P concentrations of living biomass, standing dead biomass, and lying dead biomass at young and old successional sites on the post-mining heap near Sokolov. Further, we analyzed nutrient budget in dead biomass during decomposition and we compared it with nutrient budget in decomposing cellulose. Concentrations of N and P in living biomass were highest in April and decreased during season. Lying dead biomass had a higher N concentration than N concentration contained in standing dead biomass. A litterbag experiment revealed that N was released from lying dead biomass but accumulated in standing dead biomass during decomposition. Similarly the N was accumulated in decomposing cellulose. This accumulation was highest in sites with low decomposition rate. In late summer and autumn lying biomass was derived from senescence plants, came to soil and N was released during decomposition potentially usable for C. epigejos. Standing dead biomass turned to lying biomass during winter and spring and then during its decomposition N was immobilized from soil. This mechanism could reduce availability of N for other plants and increase competitive advantage of C. epigejos regrowing from belowground organs during spring.

[Decompactization of chromosome 1 in the artificially decondensed human sperm nuclei: overall topology and non-random location of chromosome bends].

We have used FISH with microdissected chromosome arm-specific DNA probes that allow direct visualization of chromosome 1 folding in human sperm nuclei. We described the overall topology and the mode of packaging of sperm chromosome 1 and thus established new elements of ordered genome architecture in these specialized cells.

[Recognition of internal (TTAGGG)n repeats by telomeric protein TRF1 and its role in maintenance of chromosomal stability in Chinese hamster cells]. / Uznavanie vnutrennikh povtorov (TTAGGG)n telomernym belkom TRF1 i ego rol' v podderzhanii stabil'nosti khromosom v kletkakh kitaiskogo khomiachka.

Mammalian telomeres contain long tandem (TTAGGG)n repeats, which are protected by a complex of different proteins. Telomeric repeat-binding factors TRF1 and TRF2 play the key role in protection of telomeres through the formation of terminal loops (called T-loop). A T-loop isolates the 3' strand telomeric end and with this mechanism protects telomeres from the influence of enzymes of DNA reparation and telomere fusions and also interferes with the interaction of telomerase with telomeres. Many vertebrate species also contain large blocks of (TTAGGG)n sequences in pericentric and interstitial chromosome bands. The Chinese hamster genome contains a total of 18 arrays of these non-telomeric internal (TTAGGG)n sequences (ITs). Chromosome bands containing these arrays are unstable and should be protected with the help of another mechanism, rather than that using telomeres. In this study we analysed association of Green Fluorescent Protein (GFP)-tagged TRF1 in Chinese hamster V79 cells with ITs. We found that in these cells GFP-TRF1 associates with ITs in the interphase nucleus. We detected a little overlap between IT-associated GFP-TRF1 and random DSB sites visualized after the treatment of V79 cells with ionizing radiation. We found that the treatment of V79 cells with WM significantly increases the frequency of spontaneous chromosome aberrations. These WM effects are possible due to inhibiting phosphorylation of TRF1 by ATM. TRF1 is known to be eliminated from telomeres by overexpression of TANK1, which induces TRF1 poly(ADP-ribosyl)ation. We transfected V79 cells by plasmid encoding TANK1 and found that the frequency of chromosome rearrangements increased in these cells independently of their treatment by IR. Taken together, our results suggest that TRF1 may be involved in the sequence-specific protection of internal non-telomeric (TTAGGG)n repeats.

[The DNA-binding activity of the membrane protein annexin II and its interaction with antibodies to the chromatin nuclear ribonucleoprotein (alpha-RNP)]. / DNK-sviazyvaiushchaia aktivnost' primembrannogo belka anneksina II i ego vzaimodeistvie s antitelami k iadernomu ribonukleoteinu khromatina (al'fa-RNP).

By screening with labeled Alu DNA, a clone was isolated from cDNA expression library, which appeared identical in sequence to the well-known Ca-phospholipid-binding protein annexin II. To evidence the DNA-binding activity of recombinant annexin II and its presence in the cell nucleus, we have expressed full-length mouse annexin II cDNA in bacteria with pGEMEX vector. The expressed protein was studied with electrophoretic mobility shift assay and for its reaction with polyclonal antibody to chromatin-associated ribonucleoprotein (alpha-RNP), which is one of the major acid-dissolvent components of the nucleus. The obtained results confirm the DNA-binding activity of recombinant annexin II. Annexin II reacts with polyclonal antibody to rat alpha-RNP. So, annexin II is a major nuclear DNA-binding protein in mammalian cells.

A major cellular substrate for protein kinases, annexin II, is a DNA-binding protein.

We have screened a human cDNA expression library in lambda gt11 for clones encoding Alu-binding proteins using direct binding of labeled Alu DNA to recombinant phage lysates fixed on a membrane, and isolated a clone 98% identical in sequence to the well-known substrate of protein kinases, annexin II, which was suggested earlier to play a role in transduction of mitogenic signals and DNA replication. A diagnostic property of annexins is their binding to phospholipids in the presence of calcium ions, and we have found that the interaction of proteins of human nuclear extracts with Alu subsequences is suppressed by Ca/phosphatidylserine liposomes, suggesting overlapping of Ca/phospholipid- and DNA-binding domains in annexin II.