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Biomedical subjects

R B Ray

Publications and source records attributed to R B Ray.

31 records · Page 2Linked to original sources
PubMed1997

Inhibition of human immunodeficiency virus type 1 replication by a cellular transcriptional factor MBP-1.

A cellular transcriptional factor initially identified as the c-myc promoter binding protein (MBP-1) was subsequently characterized as a cell regulatory protein with multifunctional activities. In this study, the role of MBP-1 on human immunodeficiency virus type-1 (HIV-1) transcriptional activity was investigated. MBP-1 showed inhibition of HIV-1 long terminal repeat (LTR)-directed chloramphenicol acetyl transferase (CAT) activity in a transient cotransfection assay. Deletion of upstream elements of the HIV-1 LTR, including the nuclear factor kappa B (NF-kappa B) and Sp1 binding sites, did not affect the MBP-1 mediated suppression of HIV-1 LTR. The core promoter of the HIV-1 appeared to be the primary sequence involved in MBP-1 mediated inhibition. In the presence of HIV-1 TAR sequence and Tat protein, MBP-1 did not inhibit the viral promoter activity. In addition, cotransfection experiments with HIV-1 LTR and deletion mutants of MBP-1 suggested that the carboxyl terminal half of MBP-1 suppresses the HIV-1 promoter activity. Exogenous expression of MBP-1 showed suppression of HIV-1 replication in acutely infected cells and in cells cotransfected with a molecular clone of HIV-1. These results suggest that exogenous expression of MBP-1 plays an important role in the regulation of HIV-1 replication in infected cells.

DNA-Binding Proteins↗
PubMed1997

Separate domains of MBP-1 involved in c-myc promoter binding and growth suppressive activity.

We previously demonstrated that exogenous expression of MBP-1 induces rapid cell death in murine fibroblasts, and alters loss of anchorage-independent growth and tumorigenicity in human breast carcinoma cells. Here, we investigated the functional role of two different domains of MBP-1. A DNA-protein interaction study suggested that the amino-terminal half (amino acids 1-178) of MBP-1 possesses the c-myc P2 promoter binding activity. The same domain of MBP-1 also showed transcriptional repressor activity on c-myc promoter by in vitro transient expression assay. On the other hand, the carboxy terminal half (amino acids 190-335) of MBP-1 induced cell death in murine fibroblasts similar to full length MBP-1. Furthermore, exogenous protein expression from the carboxy terminal half of MBP-1 in human breast carcinoma (MCF-7) cells showed suppression of colony formation and loss of anchorage-independent growth. Results from this study suggest that MBP-1 exerts its biological effect through different functional domains.

3T3 Cells↗
PubMed1997

Chromosomal localization of the human gene encoding c-myc promoter-binding protein (MPB1) to chromosome 1p35-pter.

We report the mapping of the human gene MPB1 (c-myc promoter binding protein), a recently identified gene regulatory protein. MPB1 binds to the c-myc P2 promoter and exerts a negative regulatory role on c-myc transcription. Since exogenous expression from transfection of the MPB1 gene suppresses the tumorigenic property of breast cancer cells, there was interest in determining the chromosomal location of this gene. The human MPB1 gene was assigned to human chromosome 1p35-pter using Southern blot analyses of genomic DNAs from rodent-human somatic hybrid cell lines. A specific human genomic fragment was observed only in the somatic cell lines containing human chromosome 1 or the p35-pter region of the chromosome.

Animals↗
PubMed1997

Interrogations.

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Female↗
PubMed1996

Suppression of apoptotic cell death by hepatitis C virus core protein.

We have previously demonstrated the role of hepatitis C virus (HCV) core protein in the transcriptional regulation of cellular and unrelated viral promoters. Furthermore, the core protein in cooperation with H-ras oncogene transforms primary rat embryo fibroblast cells to the tumorigenic phenotype. In the present study, the functional role of HCV core protein was investigated to determine its potential to inhibit the onset of apoptotic cell death. Expression of HCV core protein inhibited cisplatin mediated apoptosis in human cervical epithelial cells, and apoptosis induced by the overexpression of c-myc in Chinese hamster ovarian cells. Results from these studies suggest that the core protein may have a biological implication in the pathogenesis of HCV infection.

Animals↗
PubMed1996

Hepatitis C virus core protein inhibits human immunodeficiency virus type 1 replication.

We previously demonstrated that hepatitis C virus (HCV) core protein is a strong repressor of human immunodeficiency virus type 1 (HIV-1) long terminal repeat (LTR) basal transcription. In this study, we have localized the HCV core protein-response domain to a region between nucleotides -65 and +3 within the HIV-LTR. Thus, neither the upstream negative regulatory elements, or binding sites for various transcription factors (e.g. NF-kappa B, USF-1, IL2/IL-2R) nor the downstream TAR regions were involved in HCV core-mediated repression. HCV core protein mediated repression of the basal transcriptional activity of HIV-1 LTR was abrogated by the Tat protein. Furthermore, HeLa-T4 cells expressing HCV core protein showed inhibition of HIV-1 replication after acute infection with cell-free HIV. A similar observation was also noted in CD4+ and CD4-lymphocytic cell lines cotransfected with an infectious molecular clone of HIV-1 and the HCV core protein expression vector. Thus, a repression of basal transcription prior to the accumulation of threshold levels of Tat protein appears to restrict HIV-1 transcription and modulate viral replication.

Anti-HIV Agents↗
PubMed1996

Hepatitis C virus core protein cooperates with ras and transforms primary rat embryo fibroblasts to tumorigenic phenotype.

We have previously demonstrated that hepatitis C virus (HCV) core protein regulates cellular protooncogenes at the transcriptional level; this observation implicates core protein in the alteration of normal hepatocyte growth. In the present study, the transforming potential of the HCV core gene was investigated by using primary rat embryo fibroblast (REF) cells which were transfected with or without cooperative oncogenes. Integration of the HCV core gene resulted in expression of the viral protein in REF stable transformants. REF cells cotransfected with HCV core and H-ras genes became transformed and exhibited rapid proliferation, anchor-independent growth, and tumor formation in athymic nude mice. Results from these studies suggest that the core protein plays an important role in the regulation of HCV-infected cell growth and in the transformation to tumorigenic phenotype. These observations suggest a possible mechanism for this viral protein in the pathogenesis of hepatocellular carcinoma in HCV-infected humans.

Animals↗
PubMed1995

Human breast carcinoma cells transfected with the gene encoding a c-myc promoter-binding protein (MBP-1) inhibits tumors in nude mice.

We have identified previously a gene from a human cervical carcinoma cell (HeLa) cDNA expression library that encodes a M(r) approximately 37,000 c-myc promoter-binding protein (MBP-1), which binds to the TATA box sequences of c-myc P2 promoter and exerts a negative regulatory function by down-regulating c-myc expression. In normal human tissues, this cloned gene showed variable expression. In this study, we have demonstrated that introduction of the MBP-1 gene into human breast carcinoma cells reduced their ability to invade through a basement membrane matrix in vitro but did not alter their growth rate. Human breast carcinoma transfected with MBP-1 cells showed a loss of anchorage-independent growth and also suppressed tumor formation in athymic nude mice. These results suggest the possible involvement of MBP-1 as a tumor suppressor gene in human breast carcinoma cells.

Animals↗
PubMed1995

Transcriptional regulation of cellular and viral promoters by the hepatitis C virus core protein.

The genomic region encoding the hepatitis C virus (HCV) core protein was cloned into a mammalian expression vector to study its role on the transcriptional regulation of cellular proto-oncogene and viral promoters. Using a transient transfection assay in human hepatocellular carcinoma (HepG2) cells, we demonstrate that the HCV core protein activates the human c-myc, Rous sarcoma virus long terminal repeat (LTR), and simian virus 40 (SV40) early promoters; and suppresses the c-fos promoter and human immunodeficiency virus type 1 (HIV-1) LTR activity. The transcriptional regulation of cellular proto-oncogenes by the HCV core protein suggests possible involvement of the core protein in the deregulation of normal hepatocyte growth and hepatocarcinogenesis.

3T3 Cells↗
PubMed1995

Induction of cell death in murine fibroblasts by a c-myc promoter binding protein.

The c-myc promoter binding protein (MBP-1) was identified previously from a human cervical carcinoma cell (HeLa) cDNA expression library (R. Ray and D. M. Miller, Mol. Cell. Biol., 11: 2154-2161, 1991). This study demonstrated that MBP-1 binds to the mouse c-myc P2 TATA box sequences and exerts a negative regulatory role on c-myc transcription. The role of MBP-1 on cell growth was initially examined by transfection of fibroblast cells with MBP-1 cDNA and resulted in rapid cell death. Subsequently, MBP-1 cDNA bearing an inducible promoter was introduced in murine fibroblast cells (NIH3T3) to control the expression of the exogenous MBP-1. Upon induction of exogenous MBP-1 expression, stable transfectants showed reduced c-myc expression, cell death, and DNA fragmentation. To further analyze whether c-myc inhibition mediates or complements the effect of MBP-1, the exogenous MBP-1 when introduced into NIH3T3 cells expressing deregulated human c-myc gene, cell death was interrupted. This study suggested that exogenous expression of MBP-1 induces cell death in fibroblasts by blocking cell proliferation.

Animals↗
PubMed1986

Increased synthesis of membrane macromolecules is an early response of retinal neurons to trimethyltin intoxication.

We studied the synthesis and axonal transport of proteins and glycoproteins in the visual system of adult Long-Evans rats that had received 4 weekly doses of trimethyltin hydroxide (TMT, 4 mg/kg b. wt.) by gastric intubation. One week following the last dose, an in vitro assay was used to study the rate of incorporation of radioactive precursors into various macromolecules of isolated retinas. Retinas from TMT-treated rats showed increased apparent rates of synthesis, relative to retinas from control rats, for proteins [( 35S]methionine precursor) and glycoproteins [( 3H]fucose precursor). Gel electrophoretic analysis of newly synthesized proteins indicated that the increased synthesis was a generalized effect, i.e. it was not restricted to a select subset of proteins. The axonal transport of these macromolecules by retinal ganglion cells to axons (optic tract) and nerve endings (superior colliculus) was examined in vivo following intraocular precursor injection. The amount of material transported, relative to that synthesized in the retina, was not appreciably altered in TMT-treated rats, indicating that TMT did not selectively impair axonal transport. The biochemical changes were accompanied by minimal ultrastructural alterations and little neuronal necrosis in the retina. We suggest that TMT induces increased synthesis of membrane macromolecules in retinal neurons; this may reflect an early reactive (compensatory) response rather than a regressive (degenerative) response of retinal neurons to TMT. Our data do not support the hypothesis that TMT induces a functional impairment of neuronal endoplasmic reticulum or Golgi apparatus.

Animals↗
PubMed1985

Retrograde axonal transport of endogenous phospholipids in rat sciatic nerve.

Anterograde axonal transport of phospholipids occurs at a rate of several hundred millimeters per day. However, although labeled precursors are incorporated into phospholipids in the neuronal cell bodies within several hours, these newly synthesized phospholipids are committed to transport over a much longer period of time. Thus, maximal accumulation of radioactive lipids in axons and nerve endings does not occur for several days (e.g., 4 to 7 days in rat optic tract and sciatic nerve). We have now investigated the retrograde axonal transport of endogenous phospholipid molecules in sensory neurons of rat sciatic nerve. Labeled phospholipids were delivered to axons and nerve endings of these cells by anterograde axonal transport following injection of [2-3H] glycerol into the L5 dorsal root ganglion. At various times following precursor injection two ligatures, 9 mm apart, were applied to the mid-thigh region of the sciatic nerve. Animals were sacrificed 3 to 48 hr after nerve ligation, nerves were dissected and sectioned into 5-mm segments, and phospholipid radioactivity in each segment was determined. The time-dependent accumulation of labeled phospholipids distal to the distal ligature demonstrated their retrograde axonal transport. The time course of retrograde transport for these phospholipids was more prolonged and peaked several days later than the time course for the anterograde transport phase. Further information regarding the relationship between radioactive phospholipids arriving at the nerve endings by anterograde transport, and their subsequent "turn-around" and retrograde transport back to the nerve cell bodies, was obtained by analyzing the phospholipid class label distribution of both of these transport phases at various times following precursor injection.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗