PubMed Health⌕ Search

Biomedical subjects

T J Borelli

Publications and source records attributed to T J Borelli.

8 recordsLinked to original sources
PubMed1992

Transcriptional activation of human (2'-5')oligoadenylate synthetase gene expression by the phorbol ester 12-O-tetradecanoyl-phorbol 13-acetate in type-I-interferon-treated HL-60 and HeLa cells.

(2'-5')Oligoadenylate [(2'-5')(A)n] synthetase is a key enzyme in the interferon-elicited antiviral response whose controlled expression in interferon-treated cells has been only partially elucidated. In this investigation, we have compared the modulation of the (2'-5')(A)n synthetase gene by interferon alone and by the combination of interferon and a second cellular effector, 12-O-tetradecanoyl-phorbol 13-acetate (TPA). Although TPA alone had no effect on (2'-5')(A)n synthetase, it potentiated the induction of (2'-5')(A)n of synthetase by interferon in HL-60 and HeLa cells by increasing content of its mRNA and an immunoreactive 40-kDa isoenzyme. Since TPA activates protein kinase C (PKC), other PKC-activating phorbol-ester analogues were tested and found to be effective, whereas the PKC inhibitor staurosporine reduced the potentiative activity of TPA. By using the (2'-5')(A)n synthetase gene promoter linked to a reporter gene, chloramphenicol acetyltransferase (CAT), TPA and interferon were found to result in a doubling of CAT activity compared to cells treated with interferon alone. Moreover, when nuclear extracts prepared from control cells or cells treated with TPA and interferon (IFN), separately or together, were incubated with radioactively labeled oligodeoxynucleotides containing the interferon-responsive element (IRE), TPA was shown to down-regulate an IFN-inducible IRE/protein complex. These data further suggest that TPA regulates (2'-5')(A)n synthetase gene expression at the level of transcription.

2',5'-Oligoadenylate Synthetase↗
PubMed1987

Changes in thymidine kinase activity during differentiation of HL-60 leukemic cells.

Induction of granulocyte maturation in HL-60 leukemic cells by DMSO (1.2%) or RA (1 microM) is accompanied by a 50-60% decrease in cellular thymidine kinase activity. Similarly, the differentiation of HL-60 cells into monocyte-macrophage phenotype by the addition of PMA is paralleled by a 60-80% suppression of thymidine kinase specific activity. Measurement of thymidine kinase kinetic parameters shows that the Vmax decreases from 0.7 pmol/min in control cells to 0.43 pmol/min in PMA-treated cells and to 0.38 pmol/min in RA-treated cells. The Km of the enzyme is not affected by either inducing agent and remains at 2.1 microM. Studies with PMA analogs suggest that thymidine kinase modulation is coupled to HL-60 differentiation.

Cell Differentiation↗
PubMed1986

Partial purification and characterization of phorbol ester-regulated translational inhibitor(s) in human HL-60 leukemic cells.

Addition of nanomolar concentration of the phorbol ester 12-O-tetradecanoyl phorbol 13-acetate (TPA) to the human promyelocytic HL-60 leukemia cells is associated with a cessation of cellular proliferation and a subsequent differentiation into macrophage-like cells. Because the growth rate of mammalian cells is tightly coupled to the functions of the protein synthetic machinery, we have examined whether TPA induces a change in HL-60 translational functions. Addition of control HL-60 cell extracts to rabbit reticulocyte lysates results in a pronounced inhibition of protein synthesis, while TPA-treated HL-60 cell extracts are significantly less inhibitory. The reduction in TPA-induced translational inhibitory activity can be observed after a 3-6-h treatment and reaches a maximum after 24 h. Fractionation of control cell extracts on DEAE-cellulose columns reveals two inhibitory activities, eluting at 100 and 350 mM KCl, respectively. The DEAE-100 inhibitor(s) is further resolved into two activities by heparin-agarose column chromatography (HEP-100 and HEP-250). TPA treatment of HL-60 cells for 48 h completely eliminates the HEP-250 inhibitory activity and reduces the HEP-100 and the DEAE-350 inhibitory activities by 50 and 25%. Inhibition of protein synthesis in rabbit reticulocyte lysates by DEAE-100 inhibitory activities can be partially reversed by the addition of globin mRNA while translational inhibition by DEAE-350 inhibitor(s) can be reversed by addition of eukaryotic initiation factor (eIF) 2 or fructose 6-phosphate. The DEAE-100 inhibitor(s) causes extensive degradation of radioactive polynucleotides while the DEAE-350 inhibitor(s) is capable of phosphorylating both the alpha- and the beta-subunits of the highly purified rabbit reticulocyte initiation factor eIF-2. These data show that the DEAE-100 inhibitor(s) contains a nuclease while the DEAE-350 inhibitor(s) is associated with eIF-2 alpha and eIF-2 beta protein kinases.

Animals↗
PubMed1986

The effect of ammonium ion on the induction of (2'-5')-(A)n synthetase and (2'-5')-(A)n-dependent endoribonuclease activities by interferon in mouse BALB/C 3T3 cells.

Addition of ammonium chloride to interferon (IFN)-treated mouse L cells has been reported to reduce the antiviral state. Because (2'-5')-(A)n synthetase and (2'-5')-(A)n-dependent endoribonuclease (RNase L) activities have been implicated in the establishment of the antiviral state, we wish to ascertain if ammonium ions will also impair the IFN-elicited induction of these two enzymatic activities. To test this possibility, cell-free extracts were prepared from mouse BALB/C 3T3 cells and assayed for (2'-5')-(A)n synthetase and RNase L activities. Results of these studies show that when cells were incubated with IFN (100 or 500 U/ml) and ammonium chloride (20-40 mM) for 20 h, the induction of (2'-5')-(A)n synthetase by IFN is significantly suppressed. Based on binding to the specific radioactive (2'-5')-(A)n analog, (2'-5')p3A4,3'-[32P]pCp, on cross-linking to the periodate-oxidized (2'-5')p3A4,3'-[32P]pC, or on the (2'-5')-(A)n-enhanced degradation of [3H]-polyadenylated RNA, IFN (10-250 U/ml) was shown to cause a two- to sevenfold increase in RNase L activity. The induction of RNase L by IFN was blocked by simultaneous addition of ammonium chloride. However, 20 mM or 40 mM ammonium chloride did not affect the antiviral state in BALB/C 3T3 cells (based on a plaque reduction assay with 10-500 U/ml IFN). These results suggest that the establishment of the antiviral state is not necessarily coordinated with changes in the synthetase and the RNase L activities.

2',5'-Oligoadenylate Synthetase↗
PubMed1985

In vitro translation of polyadenylated RNA isolated from control and interferon-treated human promyelocytic HL-60 leukemic cells.

Polyadenylated RNA has been isolated from control and interferon-treated HL-60 cells by centrifugation through cesium chloride and oligo(dT)-cellulose column chromatography. The affinity column-purified RNA is poorly translated in the mRNA-dependent rabbit reticulocyte lysates but is an excellent template for in vitro protein synthesis using the wheat germ cell extracts. The discrepancy in the efficiency of HL-60 mRNA utilization in the two commonly used cell-free protein synthesizing systems is attributable to an inhibitory component present in the polyadenylated RNA. This contaminant is most likely double-stranded RNA based on (i) the ability of 2-aminopurine (3-5 mM) or high concentrations of penicillium chrysogenum double-stranded RNA (10-15 micrograms/ml) to overcome the inhibition exerted by the component, and (ii) the ability of the component to promote the enzymatic conversion of ATP into 2-5A by the highly purified rabbit reticulocyte 2-5A synthetase.

2',5'-Oligoadenylate Synthetase↗
PubMed1985

Induction of human HL-60 leukemic cell differentiation by immune interferon is accompanied by an increase in NADase activity and by a decrease in DNA-binding proteins.

The effects of highly purified human immune interferon (IFN-gamma) on the differentiation of human promyelocytic HL-60 leukemic cells have been studied. The addition of 100 units/ml interferon to HL-60 cells for 5 days results in morphological changes characteristic of macrophages. At the biochemical level, there is a 3-fold increase in the specific activity of the enzyme NADase. Kinetic analysis shows that IFN-gamma causes an increase in the Vmax of NADase without affecting the apparent Km. Pulse labeling experiments with [35S] methionine show a marked change in the de novo synthesis of several proteins in the course of interferon treatment. Chromatography on DNA-agarose show that after treatment with interferon for 24 or 48 h, there is a 60-70% decrease in newly synthesized proteins which bind DNA-agarose and can be subsequently displaced from the column with 2% SDS containing buffer (from 7.7-8.7% bound in control cell extracts to 2.6-3.1% bound in interferon treated cell extract).

Cell Differentiation↗
PubMed1983

Double-stranded RNA-stimulated enzyme activities isolated from human placental extracts.

A (2'-5')An synthetase activity was isolated from human placental extracts by affinity chromatography on poly(rI) . poly(rC)-agarose. The oligonucleotide (2'-5')An was identified by (1) chromatography on PEI-cellulose and DEAE-cellulose, (2) inhibition of polypeptide synthesis in lysed rabbit reticulocytes (3) competition of the binding of pppA(pA)3,3'-[32P]pCp to rabbit reticulocyte lysates, and (4) alkaline phosphatase digestion. The synthetase activity in most placental preparations is activated by natural or synthetic dsRNA. However, in a few placental synthetase preparations, dsRNA is only marginally stimulatory and only becomes effective by prior treatment of the enzyme preparations with the calcium-dependent micrococcal nuclease. This suggests that there is an endogenous placental dsRNA contaminant in the enzyme preparations. In some synthetase preparations, a second dsRNA-stimulated product, tentatively identified as the nucleotide 5'-IMP, is also observed. Because the specific AMP deaminase inhibitor coformycin (10 microM) blocks the formation of IMP from ATP and causes a quantitative accumulation of AMP, and because the formation of IMp becomes independent of dsRNA when ADP or AMP is used in place of ATP, the presence of a dsRNA-stimulated ATP phosphohydrolase (ATPase) activity in human placenta is suggested.

2',5'-Oligoadenylate Synthetase↗