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Using computational methods for analysis of electronic databases we identified a number of human nucleotide sequences expressed predominantly in tumors. We experimentally studied one of the sequences, which is related to the UniGene database cluster Hs.633957 and located near the telomere in the chromosome 7p22.3. All the RNA sequences of the cluster Hs.633957 are non-coding and their role was not described yet, but expression pattern of the locus makes it theoretically and practically interesting. Here we studied expression of the sequence Hs.633957 in various normal and tumor tissues using reverse transcription polymerase chain reaction. Of all the normal adult tissues studied weak expression was only identified in heart and liver. It was also identified in embryonic brain and kidney. Locus Hs.633957 is expressed in tumors of various tissue origin including tumors of lung, intestines, breast, stomach, cervix, lymph nodes and others. Thus the Hs.633957 locus is expressed predominantly in tumors and may be considered a prospective tumor marker.

A phage peptide library was used to select peptides interacting with virus-neutralizing monoclonal antibodies (mAb) 2G12 which recognize a discontinuous surface epitope of HIV-1 gp120. With the published X-ray data, gp120 regions involved in the antigenic determinant were predicted. Binding with mAb 2G12 was ascribed to Trh-297, Phe-383, Tyr-384, Arg-419, Ile-420, Thr-415, Leu-416, Pro-417, Lys-421, and Trp-112. Though distant in the gp120 sequence, these residues are close in space and form the 2G12 epitope on the gp120 surface.

A phase peptide library was screened with virus-neutralizing monoclonal antibodies (MCA) 2F5 which recognize a conserved epitope of HIV-1 gp41. Phages that expose peptides specifically binding with MCA 2F5 were selected by ELISA. Amino acid sequence analysis revealed a homology to region 662-671 of HIV-1 HB10 gp160 for most peptides. The major role in recognition was ascribed to Asp-664, Lys-665, and Trp-666. The epitope-mimicking peptides were tested for immunogenicity. Antibodies to gp41 were detected in serum of immunized rabbits.

The fate of pAT153 DNA microinjected into the embryos of loach was examined. At the earliest stages of development (2 h) the high molecular weight transgenome consisting of pAT153 sequences is formed. The transgenome replicates intensively during the course of early development (until the blastula--early gastrula stages), but later the replication slows down which results in the elimination of the transgenome from the majority of embryos at more advanced stages. The analyses of the transgenome structure with the help of restriction endonucleases have shown that, after microinjection of linear DNA, the high molecular weight transgenome is formed by stochastic ligation of the sticky ends of injected molecules. Our data suggest that the transgenome formation from circular or supercoil DNA occurs after its linearization by host endonuclease.

We have shown that 8S and U2 fractions of low molecular weight nuclear RNA lmwn RNA) have tow stable conformational states with different electrophoretic mobilities. We have shown also that fractions UIa and UIb are conformational isomers. Fractions 8S and U2 are present only in one conformational state during electrophoresis, while UI RNA is always represented by both conformations. The conformation of lmwn RNAs is dependent upon conditions of isolation of nuclei and of extraction of RNA. It may change during storage of water solution of RNA at -20 degrees. Conformational changes discovered are not the result of degradation. Only one of two stable conformations of any lmwn RNA may be physiologically active, as it is the case of 5S rRNA and tRNAS. One ought to keep this in mind while studying the functions of low molecular weight nuclear RNAs.

Blot hybridization of 125I or 32P labeled 4.5S, U1 or U2 RNAs with EcoRI, HindIII, BamHI or SalG1 restriction fragments of high molecular weight DNA was performed. All these RNAs hybridized with fragments of ribosomal DNA and with 5.55-kb BamHI lines of rat. U1 ind 4.5S RNAs hybridized also with 3.6-kb HindIII lines. 125I labeled U1 RNA was hybridized with nuclear RNA in formamide. The hybrid molecules were formed which migrate in polyacrylamide gel as a broad peak slower than 28S rRNA. Our data indicate that snRNAs may participate in processing and/or splicing of hnRNA and in some other still poorly understood processes.

Possible involvement of small nuclear RNAs in transcription was explored. The fraction of small (4-8S) nuclear or cytoplasmic RNAs was isolated by Sepharose 4B gel chromatography and its influence on the RNA synthesis in isolated nuclei was studied. Small nuclear or cytoplasmic RNAs stimulated RNA synthesis in isolated nuclei both in the presence and in the absence of cytosol. On the contrary, the influence of E. coli tRNA or high molecular weight cytoplasmic RNA varied depending on the presence of cytosol. The data indicate that small nuclear RNAs may participate in transcription although the mechanisms of their involvement demand further investigation.

snRNAs of rat, mouse, hamster, chicken, frog, Drosophila and yeast were studied. Mammals are characterized by the highest content of snRNAs. Most evolutionary conservative are 8SII and 8SIII RNAs which were present in all organisms studied. On the contrary 4.5S RNA was found only in mammals and birds. These data accord with the notion that the eldest in the family of snRNAs are U3 RNA involved in pre-rRNA processing and 8S polysomal RNA, while U5-U6 RNAs are more recent evolutionary achievements. In the frog at different stages of development the relative amount and the number of fractions of snRNAs differ significantly. In embryonic and regenerating rat liver the differences are less pronounced. Extra fractions of snRNAs were found in virus transformed chick fibroblasts and in ascite hepatomas of rat.

An attempt was made to elucidate possible participation of low molecular weight nuclear RNA's (LMWN RNA's) in the transcription process. For this purpose, we studied the effect of individual fractions of LMWN RNA's, isolated by polyacrylamide gel electrophoresis, on the endogenous RNA synthesis in isolated nuclei. We have found no influence of LMWN RNA's on the incorporation of labeled precursors in the acid-insoluble material under the conditions when RNA polymerase I is predominantly active. The results obtained thus indicate that LMWN RNA's do not participate in the regulation of 45S pre-rRNA synthesis and they do not belong to limiting factors in pre-rRNA synthesis.

Small RNAs were studied in the cell-free system containing cytosol and nucleoside triphosphates. The specific incorporation of NMPs into small RNAs was shown. While AMP and CMP were incorporated predominantly into tRNA, UMP was incorporated into 4.5S, 5S, and U1 RNAs. GMP was not incorporated into small RNAs in this system. The data suggest that maturation of 4.5S, 5S, and U1 RNAs involves post-transcriptional addition of uridylate residues at their 3'-ends.