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S F Wolf

Publications and source records attributed to S F Wolf.

At least 73 records · Page 4Linked to original sources
PubMed1991

Cloning of cDNA for natural killer cell stimulatory factor, a heterodimeric cytokine with multiple biologic effects on T and natural killer cells.

Previously we have reported the purification and characterization of a novel cytokine from an EBV-transformed B cell line, RPMI 8866. This factor, termed natural killer cell stimulatory factor (NKSF), possessed pleiotropic activities including the induction of IFN-gamma from PBL, enhancement of cytotoxicity by NK cells, and stimulation of the proliferation of PBL. Purified NKSF was found to be a disulfide-linked heterodimeric protein composed of 35-kDa and 40-kDa subunits (p35 and p40). We now report the molecular cloning of cDNA for both subunits of NKSF from RPMI 8866 cellular RNA. The cDNA sequences indicate that both genes are novel, and Southern blot analysis confirmed that both cDNA are of human genomic origin. [35S]Methionine labeling indicated that cos-1 cells transfected with either p35 or p40 cDNA produced unique protein species of appropriate size. Methionine labeling of cos-1 cells cotransfected with p35 plus p40 cDNA yielded a broad band migrating between 70 and 90 kDa on a nonreducing gel. Reduction of this high molecular weight material yielded bands correlating with p35 and p40 gene products. Only culture supernatant from cotransfected cos-1 cells had a high level of NKSF biologic activity. That the high molecular weight material was responsible for this activity was indicated by the observation that biologic activity in the culture supernatant migrated at 70 to 90 kDa in a nonreducing gel. Furthermore, anti-p40 serum was able to block the biologic activities of both recombinant and natural NKSF, which indicates that it is a component of the active protein. In contrast, no activity could be detected in the supernatants of cos-1 cells transfected with p40 or p35 cDNA alone. The spectrum of biologic activity produced by cotransfected cos-1 cells was the same as NKSF purified to homogeneity from the RPMI 8866 cell line. A synergistic augmentation of some of these responses was found by the addition of IL-2 or the co-stimulators PHA or phorbol diester. The synergistic stimulation by NKSF plus IL-2 of T and NK function supports the possibility that these cytokines might prove useful in cancer therapy.

Amino Acid Sequence↗
PubMed1991

Induction of interferon gamma production by natural killer cell stimulatory factor: characterization of the responder cells and synergy with other inducers.

We previously reported that natural killer cell stimulatory factor (NKSF), a heterodimeric lymphokine purified from the conditioned medium of human B lymphoblastoid cell lines, induces interferon gamma (IFN-gamma) production from resting peripheral blood lymphocytes (PBL) and synergizes with interleukin 2 in this activity. In this study, we show that human NKSF induces IFN-gamma production from both resting and activated human PBL and from freshly isolated murine splenocytes. Human T and NK cells produce IFN-gamma in response to NKSF, but resting PBL require the presence of nonadherent human histocompatibility leukocyte antigens DR+ (HLA-DR+) accessory cells to respond to NKSF. The mechanism(s) by which NKSF induces IFN-gamma production results in accumulation of IFN-gamma mRNA, is insensitive to cyclosporin A, and synergizes with those mediated by phytohemagglutinin, phorbol diesters, anti-CD3 antibodies, and allogeneic antigens, but not by Ca2+ ionophores. The ability of NKSF to directly induce IFN-gamma production and to synergize with other physiological IFN-gamma inducers, joined with the previously described ability to enhance lymphocyte cytotoxicity and proliferation, indicates that this lymphokine is a powerful immunopotentiating agent.

Animals↗
PubMed1988

The myeloid blood cell differentiation-inducing protein MGI-2A is interleukin-6.

The mouse myeloid blood cell differentiation-inducing protein, macrophage and granulocyte inducer, type 2A (MGI-2A), was purified, and the amino acid sequence of a CNBr cleavage peptide (22 residues) was determined. This amino acid sequence is identical to the sequence found in positions 73 to 94 of mouse interleukin-6 (IL-6). Recombinant mouse IL-6 protein induces differentiation of mouse myeloid leukemic cells that are induced to differentiation by MGI-2, and monoclonal antimouse-MGI-2 antibody, which neutralizes MGI-2, also completely neutralizes this IL-6-induced differentiation. These results show that the major type of mouse myeloid differentiation-inducing protein (MGI-2A) and IL-6 are very similar and most likely identical proteins. Recombinant human IL-6 (also called interferon-beta 2 or B-cell differentiation factor), which shows only a 41% similarity to mouse IL-6, has 11 identical amino acid residues out of the 22 in the mouse MGI-2A peptide and also induces differentiation of the same myeloid leukemic cells.

Amino Acid Sequence↗
PubMed1987

Rapid hybridization kinetics of DNA attached to submicron latex particles.

We describe a novel method for attaching any DNA molecule to submicron latex beads and characterize the hybridization kinetic properties of these bead-DNA conjugates. The conjugates hybridize to DNA in solution with rates comparable to homogeneous hybridization reactions, are compatible with common hybridization conditions and are conveniently manipulated. They should thus serve as useful reagents for the fractionation and characterization of DNA and RNA.

Bacteriophage lambda↗
PubMed1985

Evidence for a relationship between DNA methylation and DNA replication from studies of the 5-azacytidine-reactivated allocyclic X chromosome.

We examined the sequence of DNA synthesis of the human active, inactive and reactivated X chromosomes in mouse-human hybrid cells. The two independent reactivants, induced by 5-azacytidine (5-azaC), expressed human hypoxanthinephosphoribosyl transferase (HPRT), and one also expressed human glucose-6-phosphate dehydrogenase (G6PD) and phosphoglycerate kinase (PGK). Restriction enzyme analysis of DNA methylation at the re-expressed loci revealed hypomethylation of CpG clusters, that characterizes the relevant genes on the active X. The transfer of active and inactive X chromosomes from the native environment of the human fibroblast to the foreign environment of the hybrid cell did not affect the specific replication sequence of either human X chromosome. The silent X chromosome when reactivated, remained allocyclic, and the first bands to replicate were the same as prior to reactivation. In one reactivant, however, further progression of replication was significantly altered with respect to the order in which bands were synthesized. This alteration in the replication of the silent X following 5-azaC-induced reactivation suggests that DNA methylation may modulate the replication kinetics of chromosomal DNA.

Animals↗
PubMed1985

Incomplete X chromosome dosage compensation in chorionic villi of human placenta.

Studies of glucose-6-phosphate dehydrogenase (G6PD) in heterozygous cells from chorionic villi of five fetal and one newborn placenta show that the locus on the allocyclic X is expressed in many cells of this trophectoderm derivative. Heterodimers were present in clonal populations of cells with normal diploid karyotype and a late replicating X chromosome. The expression of the two X chromosomes was unequal, based on ratios of homodimers and heterodimers in clones. Studies of DNA, digested with Hpa II and probed with cloned genomic G6PD sequences, indicate that expression of the locus in chorionic villi is associated with hypomethylation of 3' CpG clusters. These findings suggest that dosage compensation, at least at the G6PD locus, has not been well established or maintained (or both) in placental tissue. Furthermore, the active X chromosome in these human cells of trophoblastic origin can be either the paternal or maternal one; therefore, paternal X inactivation in extraembryonic lineages is not an essential feature of mammalian X dosage compensation.

Cells, Cultured↗
PubMed1985

Localization of glucose-6-phosphate dehydrogenase in mouse and man by in situ hybridization: evidence for a single locus and transposition of homologous X-linked genes.

By hybridizing a tritiated human genomic probe (pGD3) to metaphase chromosomes in situ, we have localized the gene for glucose-6-phosphate dehydrogenase (G6PD) in both the human and mouse complement. The locus on the intact human X chromosome is close to the telomere on the long arm, confirming the assignment based on studies of an X/autosome translocation in human-mouse hybrids. Although the signal:background ratio was reduced for the heterologous hybridization of the human probe to mouse metaphases, 20% of the grains were on the X chromosome and 93% of these were in the A region, relatively close to the centromere. The location of G6PD in mouse and man reflects intrachromosomal transposition of these homologous X loci. Genomic DNAs from mouse and man and from hybrids with human X/autosome translocations were digested with several restriction enzymes including EcoRI, PstI, and HpaII, and Southern blots were probed with 32P-pGD3. The results of the analysis also confirm the human G6PD assignment and are consistent with a single copy of the locus in the haploid genome of both species.

Animals↗
PubMed1984

Complete concordance between glucose-6-phosphate dehydrogenase activity and hypomethylation of 3' CpG clusters: implications for X chromosome dosage compensation.

To explore the molecular basis of X chromosome inactivation, we have examined the human locus for glucose-6-phosphate dehydro-genase (G6PD) in various human tissues. Studies of DNA from males and females and from somatic cell hybrids with active or inactive X chromosomes, show that two remarkably dense clusters of CpG dinucleotides in the 3' coding sequences are hypomethylated in active G6PD genes but extensively methylated in inactive ones. Reacquisition of G6PD activity, either spontaneous or induced by 5-azacytidine, is accompanied by demethylation of both clusters; however, the clusters remain methylated in reactivants that express HPRT but not G6PD. Our observations implicate these 3' CpG clusters in the transcription of G6PD and in maintenance of dosage compensation for X linked housekeeping genes.

Alleles↗
PubMed1984

Characterization of reiterated human DNA with respect to mammalian X chromosome homology.

Recombinants containing human repetitive DNA sequences were identified by dot hybridization and classified with respect to presence on the X chromosome and homology to mouse DNA. Using genomic probes that differ in number of X chromosomes, we observed extensive homology between human autosomal and X sequences. Hybridization to genomic probes that differ in species of origin indicate that these reiterated sequences have diverged between mouse and man. Eleven recombinants, each containing a different reiterated sequence(s), were hybridized in situ to metaphase chromosomes of mouse and man. These studies indicate that reiterated DNA which is homologous to the human X chromosome is more similar to DNA of human autosomes than to any murine chromosome. Therefore, it seems that reiterated DNA sequences on the human X chromosome have diverged as much during mammalian evolution as sequences on human autosomes. Moreover, the extensive modification of the original mammalian X has not interferred with the X inactivation process.

Animals↗
PubMed1984

Characterization of a cloned DNA sequence that is present at centromeres of all human autosomes and the X chromosome and shows polymorphic variation.

We have identified a human DNA recombinant (p308) with a 3.0-kilobase (kb) BamHI insert that hybridizes in situ exclusively to the centromeric region of all human autosomes and the X chromosome. This highly repetitive sequence is significantly enriched on several chromosomes, most prominently on chromosome 6. In all individuals, the majority of genomic repeats are organized as tandem 3.0-kb BamHI repeats, each containing one Taq I site; the others are organized into BamHI and Taq I repeats of variable size that have some chromosome specificity. Using mouse-human hybrids, we have defined the specific organization of this sequence on chromosomes 6, 3, and X. In some individuals, there are differences in the number and nature of the tandem repeats. These polymorphisms segregate in families as if chromosome specific. Although variable from one chromosome to another, 308 contains sequences homologous to DNA present in centric heterochromatin of essentially all human chromosomes and is evolutionarily conserved. Therefore, a significant component of pericentric DNA is similar for all human chromosomes.

Base Sequence↗
PubMed1984

Methylation of the hypoxanthine phosphoribosyltransferase locus on the human X chromosome: implications for X-chromosome inactivation.

To explore the role of DNA methylation in maintaining dosage compensation of X chromosome-linked genes and in regulating the transcriptional activity of "housekeeping" genes, we characterized DNA methylation of active, inactive, and derepressed alleles at the locus for hypoxanthine phosphoribosyltransferase (HPRT) on the human X chromosome. The methylation of Hpa II and Hha I sites in HPRT alleles on the active X chromosome was the same in all tissues. The consensus pattern includes hypomethylation of 5' clustered sites and extensive methylation of the 3' sequence. The striking feature of methylation of inactive X-chromosome alleles is nonuniformity and less extensive hypomethylation of the 5' cluster. Analysis of HPRT alleles reactivated in response to 5-azacytidine showed at least partial restoration of the consensus pattern. These observations indicate that methylation of housekeeping genes on the X chromosome is the same as that of autosomal ones and that the overall pattern and methylation of multiple sites within a cluster may cooperate to facilitate transcription. Furthermore, the fidelity of methylation of the active allele and the extensive drift in methylation of the inactive allele suggest that mechanisms involved in X-chromosome dosage compensation may be directed at the active rather than inactive X chromosome.

Alleles↗
PubMed1982

Studies of X chromosome DNA methylation in normal human cells.

Studies of methylation along 28 kilobases of X-chromosome DNA, assayed by Southern blot analysis using cloned X-chromosome-specific probes, indicates that X DNA methylation in normal human cells changes with replication, is not correlated with number of X chromosomes or transcriptional activity, and is less stable and more prevalent than when the human X is in the foreign environment of mouse-human hybrid cells. In contrast with observations of others in heteroploid cells, we observed no derepression of the inactive X in clonal populations of normal human fibroblasts treated with 5-azacytidine. This may reflect the differences in stability of the methylation of the human X in a foreign environment. Our observations preclude ubiquitous methylation differences as the molecular basis for X-chromosome inactivation.

Azacitidine↗
PubMed1982

Derepression with decreased expression of the G6PD locus on the inactive X chromosome in normal human cells.

Studies of a unique clone of skin fibroblasts from a normal 46 XX female reveal that the G6PD locus on the inactive X chromosome has been derepressed. The reactivation event occurs spontaneously, and is associated with normal karyotype, including the presence of a late-replicating X chromosome. Analysis of mouse-human hybrids with the relevant chromosome provides evidence that the derepressed locus is on the inactive X, and that reactivation is not extensive (the PGK locus is not derepressed). Nor is any general change in DNA methylation of this chromosome detectable with Hpa II and an X-specific DNA probe. Studies of the glucose-6-phosphate dehydrogenase phenotype in these heterozygous cells indicate that the reactivated X produces only half the enzyme subunits as are produced by the active X. Although this dosage difference may be related to the mutational event responsible for derepression of the locus, these observations along with other evidence suggest that loci on the inactive X, when expressed, have less activity than corresponding loci on the active X.

Clone Cells↗
PubMedDate not supplied

The use of denaturing gradient gel electrophoresis to screen for DNA sequence polymorphisms in the human factor VIII gene.

We describe the use of denaturing gradient gel electrophoresis to screen for DNA sequence polymorphisms in the human factor VIII gene. DNA fragments that differ in sequence by only a single base pair can be separated on denaturing gradient gels due to changes in their melting behavior. Previous studies have demonstrated the use of denaturing gradient gels to detect sequence changes in human genomic DNA, including mutations in the beta globin gene and polymorphisms on chromosome 20. We have begun to use denaturing gradient gels to look for polymorphisms within the human factor VIII gene. The DNA sequences of seven cloned fragments from introns in the human factor VIII gene were determined and used to predict a melting map for each fragment. The melting behavior of each cloned fragment was evaluated by electrophoresis into denaturing gradient gels. Appropriate fragments were then used as radioactive probes for hybridization to human DNA samples that had been digested with restriction enzymes. Heteroduplexes formed between the probe and genomic DNA samples were electrophoresed into denaturing gradient gels. The final positions of heteroduplex bands were determined by autoradiography. We describe a general approach for using denaturing gradient gel electrophoresis to find DNA polymorphisms, with particular emphasis on the predictive value of DNA sequence data. We compare the efficiency of polymorphism detection by denaturing gradient gel electrophoresis with detection by restriction fragment length polymorphism (RFLP) analysis. The factor VIII gene appears to have a low level of DNA sequence polymorphism.(ABSTRACT TRUNCATED AT 250 WORDS)

Base Sequence↗