Full-sized HERV-K (HML-2) human endogenous retroviral LTR sequences on human chromosome 21: map locations and evolutionary history.

One of the evolutionary mechanisms for acquisition of novel functional sequences can be domestication of exogenous retroviruses that have been integrated into the germ line. The whole genome mapping of such elements in various species could reveal differences in positions of the retroviral integration and suggest possible roles of these differences in speciation. Here, we describe the number, locations and sequence features of the human endogenous retrovirus HERV-K (HML-2) long terminal repeat (LTR) sequences on human chromosome 21. We show that their distribution along the chromosome is not only non-random but also roughly correlated with the gene density. Amplification of orthologous LTR sites from a number of primate genomes produced patterns of presence and absence for each LTR sequence and allowed determination of the phylogenetic ages and evolutionary order of appearance of individual LTRs. The identity level and phylogenetic age of the LTRs did not correlate with their map locations. Thus, despite the non-random distribution of LTRs, they have apparently been inserted randomly into the chromosome relative to each other. As evidenced in previous studies of chromosomes 19 and 22, this is a characteristic of HERV-K integration.

[ARS-activity of a DNA fragment from Bombyx mori in Saccharomyces cerevisiae cells]. / ARS-aktivnost' fragmenta DNK Bombyx mor v kletkakh drozhzhei Saccharomyces cerevisiae.

A previously cloned autonomous transgene (pr8a) of silkworm Bombyx mori inherited without changes in the structure was used to clarify the activity of its ARS in yeast cells. ARS of pr8a was also shown to maintain autonomous replication of hybrid plasmids in yeast cells. The same was true for its central 2.4-kb fragment devoid of flanking sequences.

[TAR-cloning of the short arm of human chromosome 7 in yeast and search for terminal sequences]. / TAR-klonirovanie korotkogo plecha khromosomy 7 cheloveka v drozhzhakh ipoisk terminal'nykh posledovatel'nostei.

A partial clone library of the short arm of human chromosome 7 was created in yeast artificial chromosomes (YAC) using TAR-cloning. The DNA of monochromosome somatic hybrid cells (mouse/human) RuRag 14-4-7-44 containing short arm human chromosome 7 was used for cloning. The clone library was screened for YACs with the human DNA; the mitotic stability of these YACs, the sizes of cloned fragments, and an independent clonal distribution in the chromosome were determined. Human YACs were tested for the presence of chromosome 7p telomeric sequences.

[A replication enhancer of viral origin increases the mitotic stability of yeast transformants]. / Enkhanser replikatsii virusnogo proiskhozhdeniia povyshaet mitoticheskuiu stabil'nost' transformantov drozhzhei.

It is shown in this paper that a DNA fragment of Hepatitis B virus possessing structural features of yeast replication enhancer increases the mitotic stability of yeast transformants containing hybrid plasmids of episomal and replicative types. The mitotic stability of transformants with plasmid of the replicative type and with the replication enhancer increases only in [cir+] cells. Comparison of primary sequences of HBV DNA of different subtypes revealed that only DNA has unique structural features of the yeast enhancer of replication.

Region of hepatitis B virus DNA with a homology to the yeast ARS replication enhancer.

A computer analysis of the primary sequence of hepatitis B virus (HBV) subtype ayw DNA, cloned within the pVG2 recombinant plasmid, which raises its stability in Saccharomyces cerevisiae transformants, was performed. This revealed that the structure of the HBV DNA has: two bends in the termination regions of the HBs and HBc genes, and multiple sequences with a high degree of homology to the ARS (autonomously replicating sequence) core consensus in this region of the HBs gene. DNA fragments from the HBs region (330 bp) and from the HBc region (378 bp) have an abnormal electrophoretic mobility in 8% polyacrylamide gels. The similarity of the structural motifs in the stop-region of HBs gene with the B-domain of the S. cerevisiae ARS element is discussed.