DNA sequence plays a major role in determining nucleosome positions in yeast CUP1 chromatin.

The role of DNA sequence in determining nucleosome positions in vivo was investigated by comparing the positions adopted by nucleosomes reconstituted on a yeast plasmid in vitro using purified core histones with those in native chromatin containing the same DNA, described previously. Nucleosomes were reconstituted on a 2.5 kilobase pair DNA sequence containing the yeast TRP1ARS1 plasmid with CUP1 as an insert (TAC-DNA). Multiple, alternative, overlapping nucleosome positions were mapped on TAC-DNA. For the 58 positioned nucleosomes identified, the relative positioning strengths and the stabilities to salt and temperature were determined. These positions were, with a few exceptions, identical to those observed in native, remodeled TAC chromatin containing an activated CUP1 gene. Only some of these positions are utilized in native, unremodeled chromatin. These observations suggest that DNA sequence is likely to play a very important role in positioning nucleosomes in vivo. We suggest that events occurring in yeast CUP1 chromatin determine which positions are occupied in vivo and when they are occupied.     

Antimicrobial and antiviral activities of an actinomycete (Streptomyces sp.) isolated from a Brazilian tropical forest soil

A promising producer of bioactive compounds isolated from a Brazilian tropical soil was tested for its range of antimicrobial activities. Strain 606, classified as Streptomyces sp., could not be identified up to species level, suggesting a possible new taxon. The supernatant and 10 extracts and fractions, obtained by extraction and chromatographic techniques, presented antimicrobial activity using antibiograms. The methanolic fraction was highly active against pathogenic bacteria, phytopathogenic fungi and the human pathogenic yeast Candida albicans. It also possessed high antiviral activity inhibiting the propagation of an acyclovir-resistant herpes simplex virus type 1 strain on HEp-2 cells at non-cytotoxic concentration. The strong cytotoxic effect suggests an antitumour action. This revised version was published online in August 2006 with corrections to the Cover Date.     

Effect of sublethal concentrationsof mercury, cadmium, and copper salts on the lysozyme content in fryof the lena river sturgeon acipenser baeri

The paper presents data on a change in lysozyme content in tissues of spleen, liver and heart in fry of the Lena River sturgeon exposed to the presence of sublethal concentrations of Hg2⁺, Cd²⁺, and Cu²⁺ under conditions of chronic experiment. It has been shown that the lysozyme content in fish tissues varies and has a phasic character. The amplitude of fluctuations of this parameter depends on the moment of sampling, nature of the toxicant, and structural-functional organization of the studied organs.