Type D retrovirus specific sequences in lymphocytes of the children with Burkitt-type lymphoma and their parents

Type D retroviruses cause immunodeficiency in monkey. Earlier we have revealed genetical and serological markers of type D retroviruses in children with Burkitt-type lymphoma. Using PCR/Southern blotting assay we have found sequences related to MPMV in PBMC's DNA from children with Burkitt-type lymphoma and from their parents. Moreover, the data on sequencing of virus specific sequences from one ill child and from his mother have been presented.

Human spontaneous laryngeal carcinoma HEp-2 cells are chronically infected with SRV-1 virus, a variant of simian type D retrovirus

A type D retrovirus chronically persisting in HEp-2 cells from human laryngeal carcinoma was analyzed by PCR and sequenced. This virus is most similar to SRV-1 and probably represents one of its subtypes.

The role of phosphorylation of DNA-binding proteins in regulation of transcription of the human c-myc gene

The goal of the present study was to identify transcriptional factors, to determine their specificity toward nucleotide sequences of binding sites, and to elucidate their regulatory effects on transcription of the human c-myc oncogene. Three novel phosphorylated proteins (transcriptional factors) participating in the regulation of transcription of the c-myc gene have been identified, and the following data have been obtained. A) The binding of the regulatory phosphoproteins activates in vitro transcription of the human c-myc gene. B) The recognition sites for the three discovered DNA-binding proteins, i.e., p70, p35, and p23, have been mapped in the c-myc promoter. C) The site-specific mutagenesis of p70 binding sites of the c-myc gene has been performed and the recognition sequence has been identified. The mutagenesis was carried out using the PCR technique using oligonucleotide primers with mismatches in the p70 binding site. The wild-type sequence GGGAAAAGAAAAAA showed the highest affinity toward p70, while the mutant sequence GAAAAtGAcAct exhibited a lack of affinity for the protein. The participation of p70 and other phosphorylated transcriptional factors in regulation of the human c-myc gene expression is discussed.

Enhancement of in vitro transcription of human c-myc correlates with the binding of phosphorylated protein factors from HeLa cell extract

Hela cell extract overphosphorylated with endogenous protein kinases was used for in vitro transcription of human c-myc DNA. The activation of transcription initiated from P1, P1a and P2 cap-sites was observed. Three phosphoproteins of 70, 35 and 23 kDa are found, whose binding to DNA correlates with activation of c-myc transcription. Sites of binding of these proteins to DNA are located.

Binding of proteins of HeLa S3 cell extract to oligonucleotides containing the consensus interferon-response sequence (IRS) and to the IRS-containing fragment of the human c-myc gene

The human c-myc proto-oncogene was recently found to contain a regulatory sequence similar to the consensus interferon-response sequence (IRS) of interferon-activating genes. Binding of regulatory protein(s) to this sequence of cloned fragment of c-myc, lacking the main part of 5'-nontranscribing region, regulates in vitro transcription from I1/I2 initiation sites located in the first intron of the gene. Here, we have shown that HeLa S3 nuclear extract contains different protein factors, at least two, that bind preferentially to the IRS sequence of either the c-myc gene or the interferon-dependent 6-16 gene. Moreover, each of these factors 'cross-binds' to the region of the other gene, although affinity of this interaction is lower. Binding constants of these proteins to oligonucleotide fragments of c-myc and 6-16 genes were determined. In vitro transcription of the human full-length c-myc gene (i.e. the gene containing the complete 5'-noncoding region) initiated from I1/I2 sites, that is controlled by the IRS region, was demonstrated to be blocked. A possible physiological role for the mechanisms described is discussed.

Human c-myc gene contains a regulatory site similar to consensus of interferon response sequence (IRS)

Expression of c-myc proto oncogene is regulated by multiple mechanisms. Here, we report that the consensus of the regulatory region of interferon-dependent genes, GGAAAN1-3 GAAA, was found after computer search in the 5'-terminal flank of human c-myc gene in position (-76:-67). In vitro transcription of c-myc gene fragments showed that the consensus region competes with oligonucleotide GGGAAAATGAAACT for binding to specific protein(s). This oligonucleotide was shown to bind selectively the interferon-dependent positive transcription factor. Transcription of c-myc fragments lacking 5'-terminal region up to positions -101 or +71 was initiated at two sites located in the first intron. These sites did not coincide with P1 in vivo RNA cap-site. Binding of the protein factor(s) to the regulatory region of c-myc gene -76:-67 blocked the in vitro transcription initiated in the first intron.

Expression of c-myc gene in human ovary carcinoma cells treated with vanadate

The widely accepted hypothesis of vanadate action on cells postulates that this ion inhibits protein phosphatase(s) that dephosphorylates protein phosphotyrosine residues. This inhibition causes tyrosine hyperphosphorylation of cell proteins followed by changes in physiological action of phosphoproteins resulting in stimulation of cell proliferation, expression of protooncogenes, and transient cell transformation. We have found that treatment of human ovary carcinoma (CaOv) cells with vanadate causes the increase in total protein phosphorylation from 1.5- to 2.0-fold whereas the ratio between phosphoserine, phosphothreonine, and phosphotyrosine content remains unchanged. At the same time, enhancement of c-myc gene expression (not c-fos) was observed. Hence, the increase in the ratio of phosphotyrosine to phosphoserine and phosphothreonine is not an obligatory intermediate stage before vanadate-dependent activation of c-myc expression.