Determination of inhibition sites during hydrolysis of polydeoxyribonucleotides by exonucleases III from Bacillus amyloliquefaciens and Escherichia coli

The influence of the primary structure of polydeoxyribonucleotides on the rate of hydrolysis with exonuclease III from Bacillus amyloliquefaciens and Escherichia coli was investigated. The substrates used were synthetic oligodeoxyribonucleotides and pBR 322 DNA fragments labeled with 32P at the 5'-termini of one of the chains. According to the data from polyacrylamide gel electrophoresis performed under denaturing conditions, the hydrolysis of these substrates by unsaturating concentrations of B. amyloliquefaciens and E. coli exonuclease III proceeds with several reproducible "stops". The decrease of the reaction rate was shown to take place just before the pyrimidine blocks in the digested DNA chain.     

A study of substrate specificity of DNA-methylases from Flavobacterium okeanokoites

The specificity of DNA methylase M. FokI towards oligonucleotides containing sequence 5'...GGATG.../3'...CCTAC... was investigated, and N6-methyladenine in the GGATG chain was shown to be the only product of the modification.     

Effect of the structure of oligonucleotide substrates on interaction with methylase Eco dam

The interaction of Eco dam methylase with various synthetic oligonucleotide substrates was investigated. The "imperfect" duplexes contained a normal GATC recognition sequence in one chain of the enzyme recognition site and had some defects in the complementary chain, i.e., the absence of one or several nucleotide residues or the presence of S-methyl thiophosphate groups at the 3'-termini. The 3'-S-methyl thiophosphate residue has the same effect on the methylation of oligonucleotide complexes as does the absence of internucleotide phosphate in the analogous complexes. The presence of both GA dinucleotides in the recognition site is necessary for a productive enzyme-substrate interaction. The experimental data suggest that Eco dam methylase does form a symmetrical enzyme-substrate complex which is similar to that formed by type II restriction enzymes.     

Molecular biological study of the vaccinia virus genome. IV. The late nonstructural 36K protein of vaccinia virus is vitally important

Two genetics markers: the herpes simplex virus thymidine kinase and Escherichia coli beta-galactosidase genes were inserted into the 36K protein gene of vaccinia virus located in a HindIII-P DNA fragment. An unstability of recombinant viruses with Lac(+)-phenotype were discovered. A mechanism of viruses unstable variants formation was proposed, it was confirmed by the results of hybridisation analyses of virus recombinant genomes. The importance of a late nonstructural 36K protein gene for virus reproduction was demonstrated.     

Mouse splenocyte sensitization to normal tissue antigens and natural killer activity. III. The effect of partial hepatectomy

Partial hepatectomy leads to both increasing of natural cell-mediated activity and sensibilization level (SL) of splenocytes of hepatectomized mice towards antigens of the syngeneic liver. The wave-like variability of SL was shown with sharp increase at 3, 6 and 9 days after operation. Natural killer activity was elevated on the 2nd and 10th days with a significant decrease on the 3-4th days after operation. It is assumed that the variability in the functional activity of splenocytes under study may characterized splenocytes of different populations.     

Nucleotide sequences in DNA showing preferential binding with distamycin A and acridine derivatives

The specificity of DNA X dye binding was studied. Antibiotic distamycin A was bound most strongly to the DNA sequences composed of three or more neighboring A X T pairs. Acrichin and 7-aminoacrichin proved to be weak specific inhibitors binding predominantly within the A X T regions.     

Prognostic value of non-MHC-restricted killer cell activity in lung cancer

The prognostic value of peripheral blood non-MHC-restricted cytotoxicity against the myeloid leukaemic line K562 in lung cancer patients was studied. At the time of diagnosis and before operation, 57 patients with lung cancer were tested for cytotoxicity and subsequently followed for up to 4 years. In addition, 145 lung cancer patients, 30 patients with non-neoplastic lung diseases and 76 healthy donors were tested for cytotoxicity without the follow-up, in order to correlate the stage of lung cancer and the growth rate of tumours to the level of non-MHC-restricted cytotoxicity. On average, lung cancer patients had similar non-MHC-restricted cytotoxicity to the controls. However, patients with stage II–IV diseases showed an impaired activity, stages III and IV differing significantly from the controls. This result shows that the decline in natural killer (NK) activity is associated with tumour burden. Patients with slowly growing neoplasms had stronger cytotoxic activity than patients with fast or moderately progressing disease. In the follow-up study, the whole material of 57 patients showed only a slight correlation between cytotoxicity and survival: 42% of the patients with strong activity survived for more than 2.5 years, whereas 6% of the patients with weak activity did so. In stage I patients there was no correlation between cytotoxicity and survival, nor was there a correlation in patients with stages II–IV of the disease. Hence, in our group of patients the determination of cytotoxicity preoperatively yielded no prognostic information beyound that already available from staging. However, those stage II–IV patients that survived for 1 year or more after the diagnosis and cytotoxicity tests, showed a significant correlation between cytotoxicity and survival.     

Natural killers in pregnancy: the problem of heterogeneity and the regulation of activity

Natural killer activity of pregnant women's peripheral blood lymphocytes and of cord blood was investigated. 3H-uridine labeled K-562 and human embryo fibroblasts (HEF) were used as target cells in cytotoxic test. The results of competitive inhibition test led us to a conclusion about the presence of some common K-562 and HEF surface structures recognized by NK cells. It was shown that the decline of NK activity of pregnant women and a low NK activity of cord blood were not associated with the influence of T-lymphocytes or adherent cells.     

Mutations Preventing the Phosphorylation of Human Ribosomal Protein uS15 at Y38 and S48 Reduce the Efficiency of its Transfer into the Nucleolus

Russian Journal of Bioorganic Chemistry - The ribosomal protein uS15 is one of the key proteins forming the small (40S) ribosomal subunit structure around the central domain of 18S rRNA. According...