Sequence of the cloned bseCIM gene: M.BseCI reveals high homology to M.BanIII.

The bseCIM gene, encoding M.BseCI methyltransferase (MTase) from a Bacillus stearothermophilus strain, has been previously cloned and expressed in Escherichia coli [Rina and Bouriotis, Gene 133 (1993) 91-94]. The nucleotide (nt) sequence of a 2357-bp BspMII-EcoRI fragment encoding bseCIM has now been determined. The sequence predicts a MTase of 579 amino acids (aa), 66.7 kDa. Comparison of the deduced aa sequence of M.BseCI with sequences of various MTases revealed a significant homology to m6A-MTases, especially to its isoschizomer M.BanIII from Bacillus aneurinolyticus.

Cloning and characterization of the gene encoding PspPI methyltransferase from the Antarctic psychrotroph Psychrobacter sp. strain TA137. Predicted interactions with DNA and organization of the variable region.

The gene (pspPIM) encoding the PspPI DNA methyltransferase (MTase) associated with the PspPI restriction-modification (R-M) system (5'-GGNCC-3') of Psychrobacter species TA137 has been cloned and expressed in E. coli, and its nucleotide (nt) sequence has been determined. The coding region was 1248 nt in length and capable of specifying a 46826-Da protein of 416 amino acids (aa). The predicted sequence of the MTase protein displays ten sequence motifs characteristic of all prokaryotic m5C-MTases and shows the highest similarity to other MTases that methylate the GGNCC sequence, namely M . Eco47II and M . Sau96I. All three MTases methylate the internal cytosine within their recognition sequence. Sequence similarities between M . PspPI and its isospecific M . Eco47II and M . Sau96I as well as with four other m5C-MTases that methylate the related GGWCC sequence, namely M . SinI, M . HgiCII, M . HgiBI, M . HgiEI have been also found within the variable region of these proteins. On the basis of structural information from M . HhaI and M . HaeIII, several M . PspPI residues that are expected to interact with DNA can be predicted. Furthermore, an organization of the variable region of m5C-MTases into two segments exhibiting a pattern of conserved residues and a considerable degree of structural homologies is described.

Genotoxicity studies on the organophosphorus insecticide chloracetophone.

Chloracetophone (O,O-dimethyl-2,2,2-trichloro-1-(chloroacetoxy)phosphonate), a new insecticide of the organophosphorus group of pesticides, was tested for genotoxicity in a variety of systems with different genetic end-points and varying parameters. The test systems included 2 microbial systems, Salmonella and Aspergillus for point mutations and mitotic segregation, respectively, and human lymphocyte cultures and mammalian bone marrow cells (from rats and hamsters treated acutely and subacutely) for chromosomal aberrations and micronuclei. Chloracetophone was negative in Aspergillus at concentrations of 1-500 micrograms/ml, in human lymphocyte cultures at concentrations of 2.5-40 micrograms/ml, in rats at doses of 420-21 mg/kg b.w. and in hamsters at doses of 210-42 mg/kg b.w. for chromosomal aberrations. It did not cause any increase of micronuclei in human lymphocytes and rat bone marrow cells but did cause a significant increase in hamster bone marrow cells. Chloracetophone induced base-pair substitutions in strain TA100 of Salmonella with and without metabolic activation at a concentration range of 2000-6000 micrograms/plate.

[Bsp153AI and BspM39I--new isoschizomers of PvuII restriction enzyme]. / Bsp153AI i BspM39I--novye izoshizomery restriktazy PvuII.

New restriction endonucleases, Bsp153AI and BspM39I, were isolated from Bacillus species strains 153A and M39, respectively. The enzymes recognize and cleave the nucleotide sequence [sequence: see text] and are true isoschizomers of restriction endonuclease PvuII.

[Isolation and specificity of novel restriction endonucleases Bsp40091 and AsiI, isoschizomers of BamHI]. / Vydelenie i opredelenie spetsifichnosti novykh éndonukleaz restriktsii Bsp40091 i AsiI izoshizomerov BamHI.

New type II restriction endonucleases AsiI and Bsp40091 are detected in Azotobacter species N55 and Bacillus species 4009, respectively. Purified preparations of the restriction enzymes free from interfering nucleases and phosphatases were obtained by column chromatography on phosphocellulose and heparin-sepharose (Asil) and phosphocellulose and DEAE-cellulose (Bsp40091). The yield of purified AsiI and Bsp40091 was 16 x 10(3) and 8 x 10(3) units per g of wet cells, respectively. The above restriction endonucleases recognize the 5'-G decreases GATCC-3' sequence on double-stranded DNA and cleave it as shown, thus being true isoschizomers of BamHI restriction endonuclease.

Caloric restriction and resveratrol promote longevity through the Sirtuin-1-dependent induction of autophagy.

Caloric restriction and autophagy-inducing pharmacological agents can prolong lifespan in model organisms including mice, flies, and nematodes. In this study, we show that transgenic expression of Sirtuin-1 induces autophagy in human cells in vitro and in Caenorhabditis elegans in vivo. The knockdown or knockout of Sirtuin-1 prevented the induction of autophagy by resveratrol and by nutrient deprivation in human cells as well as by dietary restriction in C. elegans. Conversely, Sirtuin-1 was not required for the induction of autophagy by rapamycin or p53 inhibition, neither in human cells nor in C. elegans. The knockdown or pharmacological inhibition of Sirtuin-1 enhanced the vulnerability of human cells to metabolic stress, unless they were stimulated to undergo autophagy by treatment with rapamycin or p53 inhibition. Along similar lines, resveratrol and dietary restriction only prolonged the lifespan of autophagy-proficient nematodes, whereas these beneficial effects on longevity were abolished by the knockdown of the essential autophagic modulator Beclin-1. We conclude that autophagy is universally required for the lifespan-prolonging effects of caloric restriction and pharmacological Sirtuin-1 activators.

Specific recombinogenic activity of a new polyene antibiotic.

A new antibiotic from Streptomyces sp., tetrapol A159, active against various fungi, a promising compound for the control of plant diseases, was studied for its genotoxic effects. It was produced at the Institute of Microbiological Preparations for Agriculture, Sofia, Bulgaria. The chemical was tested in three different test systems: a bacterial system, the Ames test for point mutations, the micronucleus test in bone marrow cells of rats for chromosomal aberrations and the fungal system of Aspergillus nidulans for mitotic recombination and aneuploidy. No increase in histidine revertants was observed in any of the TA100, TA98, TA1535 and TA1537 strains of Salmonella at concentrations ranging from 1 to 4000 mg/plate. The results were also negative in the micronucleus test of bone marrow cells at concentrations from 124 to 600 mg/kg b.w., whereas a statistically significant threefold increase of mitotic crossovers was found in Aspergillus, at concentrations from 0.5 to 2.5 mg/ml.

Isolation and characterization of CspBI, a novel NotI isoschizomer from Corynebacterium species B recognizing 5'-GC/GGCCGC-3'.

Sixty-seven bacterial strains were surveyed for the presence of type II restriction endonucleases, especially concerning super-rare-cutting enzymes. Fourteen strains were found to contain specific enzymes. One of them CspBI from Corynebacterium species B was purified and characterized as an isoschizomer of NotI, which recognizes the palindromic octanucleotide sequence 5'-GC/GGCCGC-3' and cleaves at the position shown by the arrow. A comparison between the cleavage patterns on different DNAs, obtained with partially purified endonucleases from other detected producents including some strains of Corynebacterium, Cellulomonas and Rhizobium has shown that these enzymes do not belong to super-rare-cutting restriction endonucleases.