Faculty Bibliography

Resistance to radiation leukemia virus-induced leukemia is mediated by gene(s) in the H-2D region of the MHC; a clear correlation exists between disease resistance and increased H-2Dd expression on the thymocyte surface. We have investigated the molecular basis for this stimulation of H-2Dd class I expression. Elevated H-2 mRNA and H-2 transcription are demonstrated in the infected thymocytes as compared to normal thymocytes indicating that the elevation of H-2 surface expression is the result of transcriptional activation. Gel mobility assays performed with nuclear extracts of normal and infected thymocytes and sequences 5' of the H-2Dd gene show that specific binding occurs with both extracts; the binding differs both quantitatively and qualitatively, however. DNase I protection analysis detects a protein binding site that is protected only by extracts from infected cells. The protected region contains a sequence similar to the AP-1 consensus sequence. Gel shift competition assays and UV photo-cross-linking to an oligonucleotide containing this sequence demonstrate that specific binding of an H-2 binding factor 1 occurs and that this factor is not the AP-1 binding complex. This novel binding factor, activated in vivo, might also be involved in the normal regulation of H-2 gene expression by recognizing the highly conserved binding sequence (TGACGCG) found in the 5' flanking region of many MHC class I genes. This is the first demonstration of the parallel stimulation of a DNA binding activity and increased transcription occurring in thymocytes after infection with a leukemogenic retrovirus

The receptor for gp70 envelope glycoprotein of murine ecotropic leukemia virus is essential for virus entry into the host cell and has been recently demonstrated to function as a cationic amino acid transporter. In the experiments reported herein, we compared the gene expression of the murine ecotropic retroviral receptor (ERR) and its human homolog (H13) in rapidly proliferating cells versus resting cells using four different systems. (i) The expression of ERR gene is enhanced during activation of T and B lymphocytes by concanavalin A and lipopolysaccharide, respectively. Similar enhancement is observed by adding phorbol 12-myristate 13-acetate (PMA) or calcium ionophore (A23187). These phenomena appear to involve protein kinase C; two PMA analogs, 4 alpha-phorbol and 4 alpha-PMA, lacking the ability to activate protein kinase C fail to induce elevated levels of gene expression, and the protein kinase C inhibitor, H7 [1-(5-isoquinolinylsulfonyl)-2-methylpiperazine dihydrochloride[, inhibits the enhancement induced by PMA. (ii) Friend murine leukemia virus induces rapid splenomegaly, and acute erythroleukemia in sensitive mice. Concomitantly with splenomegaly, ERR gene expression in spleen cells increases dramatically. (iii) The level of expression of the ERR or H13 gene in a variety of tumor cells is highly elevated compared with the level in noncancerous cells. (iv) H13 gene expression decreases upon terminal differentiation of the human promyelocytic leukemia cell line HL-60 into granulocytes or macrophages by dimethyl sulfoxide or PMA, respectively. These results suggest that ERR and H13 genes play an important role in cellular proliferation

The Ly-6 proteins are encoded by a recently identified multigene family. Much attention has been focused on these proteins because they may be involved in lymphocyte activation, and expression of some of them occurs at critical times in the differentiation of lymphocytes. These features make it important to investigate and to characterize further this family of molecules and the genes that encode them. To aid our investigation of these issues, we have constructed a physical map of the entire Ly-6 complex in the C57BL/6 murine genome using the combined techniques of field-inversion gel electrophoresis (FIGE), phage and cosmid genomic library screening, and two-dimensional DNA electrophoresis. This map spans approximately 1600 kb, and comparison of the FIGE map and cosmids indicates that most of the Ly-6 complex has been isolated in the cosmid clones

A novel human cDNA homologous to the murine ecotropic retroviral receptor was cloned from a cDNA library derived from a human T-cell line. The human cDNA is highly homologous to the murine counterpart (87.6% amino acid identity), and its sequence predicts a protein with 629 amino acids (approximately 68 kDa), which is 7 amino acids more than the murine counterpart (622 amino acids). The predicted protein is highly hydrophobic and contains 14 potential transmembrane-spanning domains. No other gene and protein with significant homology to the cloned human gene and the predicted protein were identified by a computer-based search of sequence data banks other than the murine T-cell early activation gene (52.5% amino acid identity) and the murine ecotropic retroviral receptor gene. The human gene is ubiquitously expressed in human tissues and conserved among mammalian species. The genomic gene was also isolated from a cosmid library derived from human lymphocytes, and its organization was elucidated. The gene mapped to human chromosome 13

Early studies showed that resistance to RadLV-induced leukaemia is mediated by gene(s) in the H-2D region of the MHC. Furthermore, these experiments correlated disease resistance with changes in H-2 expression occurring very early after virus inoculation. In the present study, we have begun to study at the molecular level this stimulation of H-2Dd class I expression in thymocytes of resistant mouse strains following infection by RadLV. The resistant strain of B10.T(6R) mice is used in these studies. When these infected thymocytes are assayed by fluorescence-activated cell sorting analysis, we can detect increased levels of H-2Dd expression on the surface of the thymocytes as early as 12 days following intrathymic injection of RadLV. RNA was prepared and examined by Northern blot analysis; H-2 mRNA levels are shown to be elevated on the order of four-fold. Nuclei were prepared from normal and infected thymocytes and the run-off transcripts were analysed by slot-blot hybridization. The rate of H-2 mRNA transcription is shown to be two- to three-fold higher in RadLV-infected thymocytes at 14 days post-infection when compared to that of normal thymocytes. These data demonstrate that elevation of H-2 surface expression following RadLV infection is the result of transcriptional activation. Extracts have been prepared from both normal and infected B10.T(6R) thymocytes and have been used in gel mobility assays in order to detect the interaction of potential trans-acting regulatory factors with sequences 5' of the H-2Dd gene. Specific binding occurs in both extracts, but the assay shows that the extracts differ both quantitatively and qualitatively; the extracts from infected thymocytes bind to additional sequences and to a higher degree than that from normal thymocytes. DNase I protection analysis locates a number of protein-binding sites, some of which are protected by extracts of either origin and some of which are only protected by extracts from infected cells. Two of these sequences are similar to the previously recognized consensus recognition sequences for the binding of AP-1 and NF-chi B. Oligonucleotides have been synthesized for both the genomic sequences being protected from DNase I digestion as well the published consensus sequences. While the DNA-binding activity in infected thymocytes for both AP-1 and NF-chi B-binding sites is increased, the binding to the genomic 'AP-1 like' binding site is activated to a considerably greater level.(ABSTRACT TRUNCATED AT 400 WORDS)

Hypericin, a polycyclic aromatic dianthroquinone, is a natural plant product with antiviral properties. We report here the development of a methodology for the extraction and quantitation of hypericin from plasma and biological fluids and the adaptation of a sensitive and selective method for detection of the compound by high-performance liquid chromatography. The methodology offers a rapid and specific means of monitoring drug blood levels in clinical and pharmacokinetic studies. The chromatographic procedure utilizes the substantial retentive properties of hypericin on reverse-phase media and detection by the strong visible absorbance maximum at 590 nm. Verification by the fluorescence spectral properties of hypericin in organic media can also be utilized. The assay is linear over a 3 log concentration range and hypericin is consistently recovered from murine, simian, and human plasma. The methodology was applied to assess the pharmacokinetic properties of hypericin in mice receiving a single bolus injection of 350 micrograms. A distribution half-life of 2.0 h and an elimination half-life of 38.5 h were calculated. We also discuss the limitations of direct analysis of hypericin by absorbance or fluorescence measurements