Mouse centromeric tandem repeats in silico and in situ

The search for all sequences containing centromeric (CEN) minor satellite (MiSat) or pericen-tromeric (periCEN) mouse major satellite (MaSat) was conducted in the whole genome shotgun (WGS) database. The sequences were checked for the presence of the known dispersed repeats using the Censor software. The presence of tandem repeats was tested using Tandem Repeat Finder (TRF). Monotonous MiSat and MaSat arrays and MaSat to MiSat array transitions were detected. Moreover, two other types of contacts were revealed: (1) MiSat transition to fragments of retroelements LINE and IAP (ERV family, intracisternal A-type particles), mainly to ORF2 and 5′-LTR containing elements; (2) MaSat transition to two tandem repeats with monomers 21 bp and 31 bp in size. The presence of the MiSat/IAP transition could be checked experimentally. The common DNA motif among the IAP fragments close to MiSat was isolated. IAP-specific primers were constructed and the fragments obtained in PCR with IAP and MiSat primers compiled the plasmid vector library. Clone n51 with the maximum length of the possible insertion (∼no. 800 bp) was selected from the library. FISH on extended chromatin fibers (fiberFISH) carried out on the n51 clone demonstrated that the main signal definitely belonged to CEN. However, the signals on the chromosome arms were also detected that could be due to the partial homology of n51 to the dispersed repeats. The duplicated fiberFISH with MiSat and n51 allowed to measure the distances between the fragments. The previously obtained MS3 sequence has some homology to IAP and CEN localization. Accordingly, the regular associations of MiSat with IAP retroelements were shown in silico and in situ. Together with the published data, the present findings suggest that retroelements or their fragments may be essential components of the normal centromere of higher eukaryotes.     

Substrate-inhibitory analysis of the cholinesterase in the freshwater oligochaete Lumbriculus variegatus (O.F. Műller, 1773; Lumbriculidae,Oligochaeta)

The substrate-inhibitory analysis has shown that single “atypical” cholinesterase (ChE) presents in tissues of freshwater oligochaete Lumbriculus variegatus (O.F. M?ller). This enzyme differs both from “typical” acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE). Specific activity of oligochaete ChE ranges 55–100 μmol ATCh g⁻¹ tissue min⁻¹ or 0.7–1 μmol ATCh mg⁻¹ protein min⁻¹, ratio of maximal rates (V) of substrate hydrolysises is 100:72:71:83 for acetyl-, propionyl-, butyryl- and acetyl-β-metylthiocholine respectively. Values of Michaelis constant (K_m) for these substrates are (1.9–2.5) × 10⁻⁴ M. The bimolecular enzyme inhibition rate constants (k_II) for organophosphorus inhibitors paraoxon, DDVP, and iso-OMPA are 10⁷, 10⁶ и 10³ mol⁻¹ | min⁻¹. ATCh and BuTCh exhibit the effect of substrate inhibition of ChE activity, while PrTCh and MeTCh do not.     

Characterization of mariner transposon from the genome of Himasthla elongata fluke

A novel DNA-transposon Hemar1 has been identified and characterized in the genome of the flatworm Himasthla elongata. This transposon is a representative of the mariner family, which is widely spread in eukaryotes; it belongs to the capitata subfamily and is highly homologous to the mariner element of the freshwater turbellarian worm Dugesia tigrina. The Hemar1 transposon has been established as a dispersed repeat and accounts for about 0.01% of the H. elongata genome. The identified Hemar1 element is a convenient tool for the further study of the functioning of mobile elements in the H. elongata genome.     

Effect of Lincocin Treatment on the Greening Process in Bean (Phaseolus vulgaris) Leaves

The effect of lincocin (a plastid protein synthesis inhibitor) treatment on the greening process of bean (Phaseolus vulgaris L.) leaves have been studied. In comparison with control leaves treated ones had a decreased rate of chloroplast development. They had a marked chlorophyll deficiency and a decreased chlorophyll a/b ratio. Some long and short wavelength forms of chlorophyll a were lacking as evidenced from the absorption spectra at 25°C and the fluorescence spectra at 77°K. The –¹⁴CO₂ fixation was inhibited by 80–90% in treated leaves. The fluorescence induced by the measuring light was greater in the treated leaves than in the control ones, and the kinetics of the decline of the relative fluorescence intensity were also different. Electron microscopic studies showed macrogranum-like structures and incomplete membrane vesicles in the treated plastids. After longer treatment a destruction of membranes was observed. The results indicate some structural and functional membrane deficiencies and instability of the membranes.