On the impossibility of the incorporation of 5-methylcytosine and its nucleosides into higher plant DNA

No radioactivity was detected in 5-methylcytosine isolated from wheat DNA after incubation of wheat seedlings with 3H-labelled 5-methylcytosine, 5-methylcytidine and 5-methyldeoxycytidine. No label from 3H-5-methylcytosine was found in DNA of seedlings. After incubation of seedlings with 3H-labelled nucleosides of 5-methylcytosine, radioactivity was discovered only in thymine of DNA. Thus 5-methylcytosine and its nucleosides can not be used in plants as direct precursors of 5-methyl cytosine residues in DNA, but nucleosides of 5-methylcytosine may be deaminated to thymidine (or deoxythymidine) and subsequently incorporated into DNA.     

Chromatography of nucleic acids, proteins and certain phages on granulated hydroxyapatite]

A modification of the classical method of hydroxyapatite synthesis is proposed. The essence of the modification is hydroxyapatite synthesis in the presence of an additional component silicic acid particles. The subsequent steps of the method are modified so, as to retain the intactness of crystals at all the stages of preparation and use of the adsorbent. The final product consists of large spherical agregates (200-250 mu in diameter) and contains about 1% of tightly bound silicic acid. It slightly differs from usual hydroxyapatite in its chromatographic properties. Granulated hydroxyapatite obtained has a high specific capacity and can be repeatedly used in experiments (up to 50 chromatographic cycles). Native high-polymeric T2 phage DNA was practically quantitatively eluated from the column. Conditions for chromatography of some proteins (lysozyme, RNase, DNase) are described. Fractionation and purification of T2 and T3 bacteriophages and TMV are carried out by means of chromatography on granulated hydroxyapatite.     

Comparative analysis of the informativeness of ISSR markers for estimating genetic diversity of horse breeds

The informativeness of six different types of ISSR markers was compared in order to evaluate genetic diversity of Mongolian, Buryat and Tuvinian horse breeds (Equus caballus). The dinucleotide-based ISSR primers ((GA)₉C, (AG)₉C, and (CA)₉G) proved to be of little use to examine genetic polymorphism among horses due to the low number of amplified and polymorphic fragments. The polymorphism information content (PIC) for the dinucleotide-based ISSR primers was 2.88 times lower than that for trinucleotide-based ISSR markers. Among the trinucleotide-based ISSR markers, CAC ISSR marker was also found to be noninformative, due to the low number of polymorphic loci identified. The highest values of the polymorphism information content (PIC) were obtained for two types of ISSR markers, based on (GAG)₆C (PIC, 3.61) and on (ACC)₆G (PIC, 2.50). Thus, the results of the present study showed that GAG and ACC ISSR markers were most informative for evaluation of genetic diversity among horses.     

Genetic Mechanisms of Resistance and Susceptibility to Leukemia in Ayrshire and Black Pied Cattle Breeds Determined by Allelic Distribution of Gene BoLA-DRB3

In the herds of Ayrshire and Black Pied cattle breeds of Russian selection, comparative analysis of allelic distribution of BoLA-DRB3 was performed in animal groups with different status of persistent lymphocytosis (PL) caused by the bovine leukemia virus (BLV). Alleles were typed by PCR–RFLP. Different spectra of BoLA-DRB3 alleles mediating susceptibility and resistance to leukemia were detected in the studied breeds. The role of amino acid motives in 1 domain of BoLA-DRB3 antigens was confirmed: ER (in positions 70–71), in resistance to leukemia and VDTY and VDTV (75–78), in susceptibility to leukemia. The nucleotide sequence of allele BoLA-DRB3.2*7with deletion of codon 65, which resulted in the changed conformation of the corresponding antigen molecule, was associated with resistance to PL. Cows of Black Pied and Ayrshire breeds with genotypes coding VDTY/VDTV (RR = 11.67, P = 0,014) and VDTY/VDTY (RR = 4.71, P = 0.022), respectively, were shown to be susceptible to PL. The role of heterozygosity level was demonstrated (estimated by BoLA-DRB3 alleles and by amino acid motives in positions 75–78 of the antigen) as an unspecific factor of resistance to PL. The lowest heterozygosity level by amino acid motives (75–78) was revealed in PL animals, for which sample inbreeding coefficients were detected: F = 0.324 and 0.084 in Ayrshire and Black Pied breeds, respectively.     

Evolutionarily-conserved gene CKAP2,located in region 13q14.3 of the human genome, is frequently rearranged in various tumors

The human CKAP2 gene, which is involved in diffuse large B-cell lymphomas, was localized via screening the GeneBridge 4 somatic cell radiation hybrid panel by means of the polymerase chain reaction (PCR). The CKAP2 gene was mapped between the WI-15460 and WI-3673 markers at the boundary between regions 13q14.3 and 13q21.1, at the distance of 14.39 cR (with 4.8 cR per cM) from the WI-5867 framework marker (lod score > 2.26). The human CKAP2 gene displayed high homology to mouse and rat expressed orthologs, A CKAP2-like sequence was found in human chromosome 14 and assumed to be a pseudogene resulting from duplication and subsequent mutations of the CKAP2 gene on chromosome 13. A possible role of the CKAP2 gene in oncogenesis associated with deletions and rearrangements of region 13q14.3-21.1 is discussed.     

Mapping of EST- and STS-markers in the human genome using a panel fo radiation hybrids

Ten DNA markers were localized in the human genome by a screening procedure against the radiation hybrid somatic cell panel (GeneBridge 4 RH Panel) using polymerase chain reaction (RH mapping method). DNA markers were developed to nucleotide sequences adjacent to NotI sites of human chromosome 3 (NotI-STS markers) and also to nucleotide sequences of human cDNA (EST markers). Three EST markers mapped (B10164, S16R and 18F5R) were localized in the human genome for the first time. Marker B10164 was found to be homologous to the nucleotide sequence of the BASP1 gene coding a major receptor protein. Markers S16R and 18F5R presumably tagged new genes, because no homologies were revealed among the nucleotide sequences presented in the databases. For four NotI-STS, more precise localization on human chromosome 3 was determined. On the basis of the data obtained, the NotI map may be integrated with other types of physical maps of human chromosome 3. RH mapping with a standard commercial panel of radiation hybrid somatic cells provided a chance to integrate the data obtained into international databases and existing integrated human chromosomal maps.