Biomedical subjects

G Gribaudo

Publications and source records attributed to G Gribaudo.

At least 19 recordsLinked to original sources

PubMed2001

The anticytomegaloviral activity of raltitrexed is abrogated in quiescent mouse fibroblasts that overexpress thymidylate synthase.

Cytomegalovirus (CMV) replication in non-proliferating cells requires the coordinated expression of the host enzymes responsible for deoxyribonucleotide synthesis. Thymidylate synthase (TS) is an essential cellular enzyme that catalyzes de novo synthesis of thymidylic acid (dTMP). In this report we show that murine CMV (MCMV) replication and DNA synthesis are inhibited in quiescent 3T6 fibroblasts by raltitrexed, a quinazoline-based folate analog that specifically inhibits TS. This antiviral activity was abrogated in LU3-7 cells, a 3T6 derivative that overproduces TS by about 50-fold. These observations indicate that the anticytomegaloviral activity of raltitrexed is associated with TS inhibition and suggest that cellular TS activity is required for efficient CMV replication in quiescent cells.

Animals↗

PubMed2001

Murine cytomegalovirus infection induces cellular folylpolyglutamate synthetase activity in quiescent cells.

Cytomegalovirus (CMV) infection stimulates the expression of cellular enzymes involved in the biosynthesis of DNA precursors. Among them, dihydrofolate reductase (DHFR) and thymidylate synthase (TS) require folate as coenzymes. In growing cells, folates are readily converted to polyglutamated forms by the cellular enzyme folylpolyglutamate synthetase (FPGS). Polyglutamated folates are selectively retained within the cell and have an increased affinity for DHFR and TS. Here we report that murine CMV (MCMV) increases the levels of the FPGS mRNAs as well as the enzymatically active FPGS protein through a mechanism that requires viral gene expression. FPGS induction by MCMV would provide the necessary supply of polyglutamated folates to the cellular enzymes involved in the biosynthesis of deoxyribonucleotides, enabling viral DNA replication to take place in quiescent cells.

3T3 Cells↗

PubMed2001

The catechol 1,2 dioxygenase system of Acinetobacter radioresistens: isoenzymes, inductors and gene localisation.

Two different isozymes (Iso A and Iso B) of catechol 1,2 dioxygenase (C1,2O) were isolated from cultures of A. radioresistens grown in two different media, containing phenol and benzoate respectively. In the phenol medium the bacteria expressed about 90% of Iso A, whereas in the benzoate medium the Iso A/Iso B ratio was 40:60. The two proteins have different molecular masses, isoelectric points and N-terminal sequences that are not consistent with simple post-translational modifications. Furthermore, their behaviour differs at high temperatures (42 degrees C-47 degrees C) and at moderately acidic pH (pH 6.0): Iso A proved to be the more stable under conditions of environmental stress. Hybridisation analysis with an A. calcoaceticus catA-derived probe revealed that A. radioresistens C1,2O proteins are encoded by two chromosomally located genes. Bidimensional electrophoresis (2DE) maps of crude extracts of cells grown in different carbon sources (phenol, benzoate and acetate) clearly demonstrated a differential induction pattern for the two proteins. The hypothesis of a double set of genes, one for benzoate catabolism and the other for phenol catabolism, is discussed, and analogies are drawn with other known C1,2Os.

Acinetobacter↗

PubMed2000

The retinoblastoma protein is an essential mediator that links the interferon-inducible 204 gene to cell-cycle regulation.

We have previously demonstrated that overexpression of p204, a member of the Ifi 200 gene family, inhibits growth, delays G0/G1 progression into S phase, and impairs E2F-mediated transcriptional activity. In this study, we show that p204 directly binds the retinoblastoma protein (pRb) in vivo to exert its activity. Transient p204 overexpression in Rb+/+ mouse embryo fibroblasts (MEF) inhibits cell proliferation, but does not affect cell growth in MEF derived from Rb-/- mice. Two human cell lines, Saos2 and C33A, bearing an inactive pRb, but not primary human embryo fibroblasts, are resistant to the p204 antiproliferative activity. p204 contains two 200 amino acid motifs, designated as type a or b domains, each containing a canonical Rb binding motif (LXCXE). When dominant-negative mutants at the Rb binding motif were transfected in Rb+/+ MEF, p204 lost its ability to inhibit cell growth, delay cell transition from G1 to S phase, and impair DNA synthesis. Moreover p204 overexpression in Rb+/+ MEF led to a significant decrease of both DHFR and PCNA proteins, two S phase markers. By contrast, this effect was not observed when Rb+/+ MEF were transfected with a p204 mutated at both Rb binding sites. Finally, overexpression of the LXCXE p204 mutant rendered Rb+/+ MEF resistant to the IFN-alpha antiproliferative activity, in comparison to the untransfected Rb+/+ MEF. As expected, Rb-/- cells were unsensitive to the IFN-alpha induced growth inhibition. Taken as a whole, these results suggest that (i) p204 contributes to the IFN-alpha antiproliferative activity and (ii) the primary target of p204 leading to efficient G1 arrest as well as to blockade of DNA replication from G1 phase is the pRb regulatory system.

3T3 Cells↗

PubMed2000

The thymidylate synthase inhibitor ZD1694 potently inhibits murine and human cytomegalovirus replication in quiescent fibroblasts.

Tomudex (ZD1694) is a quinazoline-based folate analog and a powerful inhibitor of cellular thymidylate synthase and is approved in Europe for use in oncology. Here the first evidence of its activity against murine and human cytomegalovirus (MCMV and HCMV) is reported. ZD1694 irreversibly inhibited the replication and DNA synthesis of both viruses in quiescent fibroblasts. The corresponding 50% effective concentrations were 0.006 and 0.002 microM respectively, whereas the 50% cytotoxic concentration was >10 microM for both murine and human quiescent fibroblasts. A similar antiviral effect was observed against two ganciclovir-resistant HCMV strains isolated from AIDS patients. Taken as a whole these results demonstrate that cellular thymidylate synthase plays an essential role in viral replication and that ZD1694 merits further investigation as anticytomegaloviral agent.

Animals↗

PubMed2000

Chronic myeloid leukemia cells resistant to interferon-alpha lack STAT1 expression.

INTRODUCTION: Interferon-alpha (IFN) plays a role in the management of different neoplasias, particularly those of hematological origin. The mechanisms of action of IFN are still poorly understood and the individual response is unpredictable. In the present study, the pattern of intracellular gene expression following in vitro and in vivo exposure of chronic myeloid leukemia (CML) cells to IFN was evaluated and correlated with the response to in vivo treatment with IFN. MATERIALS AND METHODS: CML patients in different phases of the disease were studied. The pattern of expression of two IFN-inducible proteins involved in IFN-mediated biological activities, the p91 and p84 proteins (STAT1alpha and STAT1beta), components of the IFN-stimulated gene factor 3 (ISGF3) complex and the enzyme 2'-5' oligoadenylate synthetase (2'-5' OASE) were investigated by Western blot in peripheral blood mononuclear cells stimulated or not in vitro by IFN. RESULTS AND CONCLUSIONS: In 6/9 patients evaluated before starting treatment, STAT1 was expressed either constitutively or after in vitro stimulation by IFN. In three cases, STAT1 remained negative even after in vitro activation. The pattern of protein expression correlated with the subsequent hematological response to prolonged in vivo IFN administration: the presence of STAT1 being associated with the clinical response to IFN and the absence and non-inducibility of STAT1 with resistance to IFN. This was further substantiated by studies carried out in ten patients analyzed at the time of a documented clinico-hematological response or resistance to the in vivo administration of IFN. Finally, in order to establish whether the pattern of response to IFN treatment could be predicted at diagnosis, cells cyropreserved at diagnosis from patients with a documented complete response, confirmed also by cytogenetic negativity, or resistance, were studied. While complete responders proved STAT1 positive, none of the four resistant cases ever expressed STAT1. The expression of 2'-5' OASE did not correlate with the clinical response to IFN. This study documents the pivotal role of STAT1 in the in vitro and in vivo responses of CML cells to IFN. The constitutive or induced presence or absence of STAT1 shows a predictive correlation with the response or resistance to treatment with IFN and could be utilized to identify, at diagnosis, resistant patients who may be spared an expensive and unnecessary prolonged IFN administration.

Adult↗

PubMed2000

Murine cytomegalovirus stimulates cellular thymidylate synthase gene expression in quiescent cells and requires the enzyme for replication.

Herpesviruses accomplish DNA replication either by expressing their own deoxyribonucleotide biosynthetic genes or by stimulating the expression of the corresponding cellular genes. Cytomegalovirus (CMV) has adopted the latter strategy to allow efficient replication in quiescent cells. In the present report, we show that murine CMV (MCMV) infection of quiescent fibroblasts induces both mRNA and protein corresponding to the cellular thymidylate synthase (TS) gene, which encodes the enzyme that catalyzes the de novo synthesis of thymidylic acid. The increase in TS gene expression was due to an increase in gene transcription, since the activity of a reporter gene driven by the mouse TS promoter was induced following MCMV infection. Mutagenesis of the potential E2F-responsive element immediately upstream from the TS essential promoter region abolished the virus-mediated stimulation of the TS promoter, suggesting that the transactivating activity of MCMV infection was E2F dependent. Cotransfection experiments revealed that expression of the viral immediate-early 1 protein was sufficient to mediate the increase in TS promoter activity. Finally, MCMV replication and viral DNA synthesis were found to be inhibited by ZD1694, a quinazoline-based folate analog that inhibits TS activity. These results demonstrate that upregulation of cellular TS expression is required for efficient MCMV replication in quiescent cells.

3T3 Cells↗

PubMed2000

Expression of an altered ribonucleotide reductase activity associated with the replication of murine cytomegalovirus in quiescent fibroblasts.

Ribonucleotide reductase (RNR) is an essential enzyme for the de novo synthesis of both cellular and viral DNA and catalyzes the conversion of ribonucleoside diphosphates into the corresponding deoxyribonucleoside diphosphates. The enzyme consists of two nonidentical subunits, termed R1 and R2, whose expression is very low in resting cells and maximal in S-phase cells. Here we show that murine cytomegalovirus (MCMV) replication depends on ribonucleotide reduction since it is prevented by the RNR inhibitor hydroxyurea. MCMV infection of quiescent fibroblasts markedly induces both mRNA and protein corresponding to the cellular R2 subunit, whereas expression of the cellular R1 subunit does not appear to be up-regulated. The increase in R2 gene expression is due to an increase in gene transcription, since the activity of a reporter gene driven by the mouse R2 promoter is induced following virus infection. Cotransfection experiments revealed that expression of the viral immediate-early 1 protein was sufficient to mediate the increase in R2 promoter activity. It was found that the viral gene M45, encoding a putative homologue of the R1 subunit, is expressed 24 and 48 h after infection. Meanwhile, we observed an expansion of the deoxyribonucleoside triphosphate pool between 24 and 48 h after infection; however, neither CDP reduction nor viral replication was inhibited by treatment with 10 mM thymidine. These findings indicate the induction of an RNR activity with an altered allosteric regulation compared to the mouse RNR following MCMV infection and suggest that the virus R1 homologue may complex with the induced cellular R2 protein to reconstitute a new RNR activity.

Animals↗

PubMed1999

The antiproliferative activity of the murine interferon-inducible Ifi 200 proteins depends on the presence of two 200 amino acid domains.

Interferon-inducible proteins, p200, have a modular organization consisting of one (p203) or two (p202 and p204) 200 amino acid motifs, designated as type a or b domains. The relationship between this domain organization and the antiproliferative activity was investigated by generating a hybrid protein with the 204 a domain upstream from the 203 b domain. This 204a/203b protein inhibits the proliferation of transfected cells, delays G0/G1 progression into S phase following serum restimulation, and inhibits the E2F-mediated transcriptional activity. These results demonstrate for the first time that both a and b domains are needed for inhibition of proliferation by the Ifi 200 proteins.

3T3 Cells↗

PubMed1999

In vitro and in vivo expression analysis of the interferon-inducible 203 gene.

The interferon (IFN)-inducible protein family 200 is encoded by structurally related genes located on mouse chromosome 1. The encoded proteins so far characterized and designated p202, p204, and pD3 contain at least one copy of a conserved 200 amino acid domain in addition to other regions that are different or missing among the various family members. We have recently characterized a cDNA clone (203 cDNA) encoding a 408 amino acid protein bearing structural similarities to p202 and p204. Here, we report its pattern of expression in vitro and in vivo. In vitro, the mRNA and protein encoded by the 203 gene were increased by IFN-alpha in several cell lines of different histologic origin. By contrast, no significant induction was observed in vivo in mice from C57BL/6 and BALB/c strains even after treatment with the IFN-inducer poly rI:rC. In addition, the constitutive expression of 203 gene was restricted to some myeloid and lymphoid tissues, namely, thymus, bone marrow, and spleen. Comparison of the expression pattern of the 203 and 202 genes in three mouse strains revealed that they exhibit a differential inducibility by IFN and a reciprocal expression pattern. The 203 mRNA was constitutively expressed in C57BL/6 and BALB/c mice and undetectable in the spleen of DBA/2 mice. The 202 mRNA was strongly induced by poly rI:rC in the spleen of DBA/2 and BALB/c mice but absent in C57BL/6 mice. Southern analysis revealed a restriction fragment length polymorphism in the 203 locus. Taken as a whole, these results demonstrate a remarkable difference in the in vivo IFN responsiveness of two members belonging to the same gene family with a similar degree of IFN inducibility in vitro. Moreover, the reciprocal expression pattern in C57BL/6 and DBA/2 mice could mean that p203 and p202 play the same role in a mouse strain in which only one of them is expressed.

3T3 Cells↗

PubMed1999

Human cytomegalovirus stimulates cellular dihydrofolate reductase activity in quiescent cells.

Human cytomegalovirus (HCMV) productively infects quiescent fibroblasts in which the levels of deoxynucleotide triphosphates (dNTPs) and cell functions involved in DNA metabolism are very low. Since sufficient dNTPs levels are essential for human HCMV replication, host cell enzymes involved in the biosynthesis of dNTPs might be expected to be stimulated by viral infection in quiescent cells. We report that HCMV infection of quiescent fibroblasts stimulates the activity of cellular dihydrofolate reductase (DHFR), a key enzyme in DNA precursor synthesis. We also demonstrate that suppression of DHFR activity by the specific inhibitor methotrexate prevents HCMV replication and DNA synthesis. These observations indicate that induction of DHFR activity by HCMV is required for efficient viral replication in quiescent fibroblasts.

Cells, Cultured↗

PubMed1997

Molecular cloning and expression of an interferon-inducible protein encoded by gene 203 from the gene 200 cluster.

We report here the complete coding sequence of a 203 cDNA, a member of the interferon-inducible Ifi 200 gene family. By combining reverse-transcriptase PCR and rapid amplification of cDNA ends (RACE) techniques we have obtained a 3.8-kb cDNA corresponding to a 203 mRNA. When used as a probe in northern analysis, its 3' segment hybridized to a 3.8-kb interferon-inducible mRNA, whereas the 5'-end additionally hybridized to a less abundant interferon-inducible 1.8-kb mRNA. Nucleotide sequence analysis revealed that the two mRNAs share the 5'-untranslated region and the same open reading frame, which encodes a hydrophilic protein composed of 408 amino acids. The difference between them is due to a 3'-untranslated region extended by alternative polyadenylation site selection. Furthermore, 203 mRNA was found to be inducible by interferon-alpha in various murine cell lines. Using polyclonal antibodies raised against a segment specific for the 203 protein, we established that p203 protein levels increase on treatment with interferon-alpha in murine fibroblasts and that p203 is located in the nucleus.

3T3 Cells↗

PubMed1996

The murine cytomegalovirus immediate-early 1 protein stimulates NF-kappa B activity by transactivating the NF-kappa B p105/p50 promoter.

The transcription of murine cytomegalovirus (MCMV) immediate-early (IE) genes is regulated by a large and complex enhancer containing several consensus binding sites for the ubiquitous transcription factor NF-kappa B. To verify whether MCMV, like the human CMV, can activate NF-kappa B-dependent transcription, we transfected murine embryo fibroblasts cells with a construct containing three copies of the NF-kappa B element in front of the homologous minimal MCMV IE1-3 promoter. Upon MCMV infection the reporter gene activity was transactivated to about three-fold above the basal level. The specificity of this transactivation was demonstrated by the lack of any significant effect on the activity of DNA constructs containing either a mutated NF-kappa B trimer or an ATF/CRE trimer. Gel shift assays with a NF-kappa B probe revealed that MCMV infection activated DNA binding proteins showing NF-kappa B characteristics. The DNA-binding activity remained elevated during the course of infection and was associated to an increase in the steady-state mRNA levels for the NF-kappa B subunit p105/p50. Since the promoter of the p105/p50 gene was transactivated by MCMV infection during the period in which the IE proteins are expressed, the role of the two major IE transcriptional regulatory proteins was examined. In cotransfection experiments, the IE1 protein transactivated the p105/p50 promoter, whereas the IE3 was ineffective in increasing the transcription of the reporter gene. Taken as a whole, these results demonstrate that MCMV, like its human counterpart, regulates the cellular NF-kappa B activity needed for the initial induction of the IE genes and the progression of the viral replicative cycle.

3T3 Cells↗

PubMed1995

Interferon-alpha inhibits the murine cytomegalovirus immediate-early gene expression by down-regulating NF-kappa B activity.

Transcription of murine cytomegalovirus (MCMV) immediate-early (IE) genes is regulated by the interaction of cellular transcription factors with a strong viral enhancer controlling promoters flanking both sides of the regulatory sequence. We have previously demonstrated that interferon-alpha (IFN-alpha) inhibits MCMV replication by impairing the transcription of IE genes. To define the cis-acting elements and trans-acting factors involved in this inhibition, permissive murine fibroblasts were transferred with DNA constructs containing the chloramphenicol acetyl transferase reporter gene and portions of the IE enhanced. The region spanning -1185 to -259 relative to the IE1-3 promoter was sufficient to allow IFN-alpha-induced inhibition. Since this segment contains several NF-kappa B sites, cells were transfected with a construct containing three copies of NF-kappa B element in front of the homologous minimal IE1-3 promoter. Upon IFN-alpha treatment the reporter gene activity was strongly reduced, indicating that NF-kappa B binding site is sufficient to confer inhibition. The specificity of this inhibition was demonstrated by the lack of a significant effect on the activity of DNA constructs containing either a mutated NF-kappa B trimer or an ATF/CRE trimer. Gel shift assays with NF-kappa B probes revealed that MCMV infection activated NF-kappa B proteins, whereas IFN-alpha treatment significantly reduced their ability to bind NF-kappa B sites. In cotransfection experiments using various NF-kappa B subunit expression vectors and a reporter driven by three copies of an NF-kappa B element, activation of NF-kappa B-dependent transcription was observed with expression of p65 or combinations of p50-p65. Taken as a whole, these results suggest that IFN-alpha inhibits MCMV IE gene enhancer activity by mechanisms that decrease the availability of virus-induced NF-kappa B transcriptionally active in the nuclei of infected cells.

3T3 Cells↗

PubMed1995

Induction of 2.5 OAS gene expression and activity is not sufficient for IFN-gamma-induced neuroblastoma cell differentiation.

We showed earlier that interferon-gamma is a powerful inducer of differentiation of human neuroblastoma (NB) cells. Although 2',5' oligo-adenylate synthetase (2,5 OAS) may play a role in mediating the anti-proliferative and/or differentiative effects of interferons (IFNs), direct evidence is lacking. We have investigated gene and protein expression of the 4 different 2,5 OAS isoforms and their cumulative enzymatic activity in a previously characterized IFN-gamma-sensitive human NB cell line, LAN-5. Analysis of total and poly(A)+ RNA by Northern blot and RT-PCR indicated that expression of the mRNA coding for the 40-, 46-and 69-kDa isoforms was induced in a time- and dose-dependent manner, reaching a maximum after a 36-hr treatment with 1000 IU/ml of IFN-gamma. In the absence of treatment, only the mRNA for the 69-kDa isoform was detectable by RT-PCR. Inhibition of transcription with actinomycin D showed that 2,5 OAS mRNA was quite stable, with a half-life of about 4 hr. With respect to the protein content, no 2,5 OAS isoform was present in proliferating LAN-5 cells; following IFN-gamma treatment, the 100-, 69-and 46-kDa isoforms became detectable. Accordingly, 2,5 OAS enzymatic activity, virtually undetectable in untreated LAN-5 cells, increased up to 132 pmol oligoadenylate/micrograms protein/hr after 48 hr of treatment, then slowly decreased, remaining detectable up to 96 hr. However, the 2,5 OAS proteins required an exogenous activation by synthetic dsRNA to exert enzymatic activity. It is therefore conceivable that they do not play a biological role in NB cell functions. Moreover, an increase in 2,5 OAS enzymatic activity was also observed in NB cells resistant to the differentiation-promoting activity of IFN-gamma, further suggesting that 2,5 OAS induction was not sufficient to trigger IFN-gamma-dependent neuronal maturation. Furthermore, other differentiation-inducing agents, such as retinoic acid and cytosine arabinoside, or complete proliferative arrest produced by serum deprivation, failed to enhance 2,5 OAS activity, thus indicating that the 2,5 OAS system is not directly involved in mediating other differentiative pathways of NB cells.

2',5'-Oligoadenylate Synthetase↗

PubMed1995

Mechanisms of viral inhibition by interferons.

Interferons (IFNs) are a family of related proteins grouped in four species (alpha, beta, gamma and omega) according to their cellular origin, inducing agents and antigenic and functional properties. Their binding to specific receptors leads to the activation of signal transduction pathways that stimulate a defined set of genes, whose products are eventually responsible for the IFN antiviral effects. Their action against viruses is a complex phenomenon. It has been reported that IFNs restrict virus growth at the levels of penetration, uncoating, synthesis of mRNA, protein synthesis and assembly. This review will attempt to evaluate evidence of the involvement of the IFN-inducible proteins in the expression of the antiviral state against RNA or DNA viruses.

Animals↗

PubMed1995

cAMP response element of murine cytomegalovirus immediate early gene enhancer is transactivated by ras oncogene products.

Products of ras oncogenes strongly stimulate the activity of the reporter gene, chloramphenicol acetyltransferase (CAT), driven by a 1.2 kb fragment of the murine cytomegalovirus (MCMV) immediate early (IE) gene enhancer (pCMVCAT). To define the role of proteins binding to the unique cAMP response element (CRE) present in the IE enhancer, NIH 3T3 cells were cotransfected with prasZip6 plasmid, a mammalian expression vector containing a v-Ha-ras cDNA, together with p(delta)ACMVCAT (pCMVCAT without the CRE sequence). Lower stimulation of CAT activity was indeed observed upon deletion of the CRE sequence. Decreased levels of p(delta)ACMVCAT were also observed in cell lines carrying stably transfected ras oncogenes. Further support for the role of the CRE sequence in MCMV enhancer activation comes from the finding that v-Ha-ras expression increases the activity of a reporter gene, beta-galactosidase, driven by three tandem copies of CRE sequence about six-fold. Moreover, this transactivation was prevented by cotransfection of the dominant inhibitor mutant Ha-ras (Leu-61; Ser-186) and was not suppressed by cotransfection of Ha-ras (Asn-17), suggesting that the effect is due to activated ras protein, rather than normal p21ras. Finally the transactivation observed is accompanied by an increase in nuclear proteins binding to a labelled oligonucleotide homologous to the CRE sequence, as shown in a gel retardation assay. These results suggest that the CRE element contributes to the transactivation of the MCMV IE gene enhancer by ras oncogenes.

3T3 Cells↗

PubMed1994

Characterization of nuclear factors involved in 202 gene induction by interferon-alpha in murine leukemia cells.

The 5' terminal flanking region of the interferon-inducible gene, 202, contains an interferon-stimulable response element (ISRE), called a GA box, that confers inducibility by interferon(IFN)-alpha, but not by IFN-gamma, on a reporter gene, such as the chloramphenicol acetyltransferase (CAT). Nuclear extracts from L1210 murine leukemia cells, stimulated for various periods of time with IFN-alpha, were mixed with 32P-labeled GA box and analyzed for the presence of retarded complexes in electrophoretic-mobility-shift assays. In addition to a few constitutive retarded complexes, an inducible GA box-binding activity (GAbf-1) appeared after 5 min, peaked at about 2 h, and was still abundant 12 h after IFN-alpha treatment. In the cytoplasmic fraction GAbf-1 was not detectable before 30 min, continued to increase up to 2 h, but had disappeared within 12 h. GAbf-1 activity was not observed in nuclear extracts treated with IFN-gamma, and was not inhibited by prior treatment with the protein-synthesis inhibitor cycloheximide. When the binding properties of GAbf-1 were compared with those of ISGF-3, the primary transcriptional activator for IFN-alpha-induced genes, a different pattern of retarded complexes was observed. Moreover, as observed by immunoblotting analysis, nuclear extracts from IFN-alpha-treated L1210 cells did not contain the p91/84 subunit of the ISGF3, the best characterized nuclear complex activated by IFN-alpha. Altogether these results indicate that GAbf-1 may be a novel transcription factor exploited by IFN-alpha to activate the 202 inducible gene in murine pre-B leukemia cells.

Animals↗