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M Sioud

Publications and source records attributed to M Sioud.

69 records · Page 4Linked to original sources
PubMed1990

The complete nucleotide sequences of the heavy chain variable regions of six monospecific rheumatoid factors derived from Epstein-Barr virus-transformed B cells isolated from the synovial tissue of patients with rheumatoid arthritis. Further evidence that some autoantibodies are unmutated copies of germ line genes.

Structural studies of human monoclonal rheumatoid factors (RF) derived from patients with monoclonal gammapathies have revealed a restriction in the usage of heavy and light chain variable regions. These studies have suggested that germline genes with little if any somatic mutation can generate RF specificity. However, there is no information presently available regarding the primary structure and genetic origin of RF in rheumatoid arthritis. In this study, we have isolated and sequenced the VH regions of six monoclonal RF derived from the synovial membranes of two patients with rheumatoid arthritis and one with the juvenile polyarticular form of the disease. We found the same VH families as previously reported among monoclonal paraproteins with RF activity. However, our sample was diverse regarding the VH, DH, and JH gene segments used. Among VHI RF there was conservation in the length of CDRIII as well as restriction in the amino acid generated at the V-D junction, as opposed to VHIII RF and non-RF VHI molecules that are highly heterogeneous in these two aspects. We also found that different JH gene segments may contribute to RF specificity. The VH, DH, and JH elements of one RF in our study all had clearly identifiable germline counterparts. This RF displays a nearly germline configuration throughout its entire heavy chain and represents another example of an autoantibody encoded by one of the VH gene segments from the preimmune fetal repertoire.

Arthritis, Rheumatoid↗
PubMed1989

Ciprofloxacin and etoposide (VP16) produce a similar pattern of DNA cleavage in a plasmid of an archaebacterium.

The fluoroquinolone ciprofloxacin, an inhibitor of eubacterial DNA gyrase, induces single- and double-stranded DNA breaks in the plasmid pGRB-1 from the halophilic archaebacterium Halobacterium GRB when the cells are treated by this drug in a magnesium-depleted medium. This reaction is prevented by a dose of novobiocin known to specifically inhibit DNA gyrase. Cleavage of pGRB-1 DNA induced by either ciprofloxacin or the antitumoral drug etoposide (VP16) produces DNA fragments of identical lengths. These results indicate that ciprofloxacin, novobiocin, and etoposide have a common target in Halobacterium GRB: an archaebacterial type II DNA topoisomerase. The similarity of DNA cleavage patterns induced by ciprofloxacin and etoposide is a new and strong argument that quinolone and epipodophyllotoxins have the same mode of interaction with the DNA-DNA topoisomerase II complexes. The plasmid pGRB-1 could be used to prescreen in the same system both antibiotics that inhibit bacterial gyrase and antitumoral drugs that inhibit eukaryotic DNA topoisomerase II.

Ciprofloxacin↗
PubMed1989

Studies on DNA polymerases and topoisomerases in archaebacteria.

We have isolated DNA polymerases and topoisomerases from two thermoacidophilic archaebacteria: Sulfolobus acidocaldarius and Thermoplasma acidophilum. The DNA polymerases are composed of a single polypeptide with molecular masses of 100 and 85 kDa, respectively. Antibodies against Sulfolobus DNA polymerase did not cross react with Thermoplasma DNA polymerase. Whereas the major DNA topoisomerase activity in S. acidocaldarius is an ATP-dependent type I DNA topoisomerase with a reverse gyrase activity, the major DNA topoisomerase activity in T. acidophilum is a ATP-independent relaxing activity. Both enzymes resemble more the eubacterial than the eukaryotic type I DNA topoisomerase. We have found that small plasmids from halobacteria are negatively supercoiled and that DNA topoisomerase II inhibitors modify their topology. This suggests the existence of an archaebacterial type II DNA topoisomerase related to its eubacterial and eukaryotic counterparts. As in eubacteria, novobiocin induces positive supercoiling of halobacterial plasmids, indicating the absence of a eukaryotic-like type I DNA topoisomerase that relaxes positive superturns.

Archaea↗
PubMed1988

Novobiocin induces accumulation of a single strand of plasmid pGRB-1 in the archaebacterium Halobacterium GRB.

Treatment of Halobacterium GRB cells with the DNA topoisomerase II inhibitor novobiocin induces the accumulation of a circular single-stranded DNA form of the plasmid pGRB-1. This form corresponds to the transcribed strand of pGRB-1. A tiny amount of this form is detectable in untreated cells. The induction of single-stranded pGRB-1 molecules by novobiocin is abolished when cells are pretreated with aphidicolin or anisomycin, which inhibit halobacterial DNA replication and protein synthesis, respectively. These results suggest that the single-stranded form of pGRB-1 is generated in the course of plasmid replication.

Bacterial Proteins↗
PubMed1988

Novobiocin induces positive supercoiling of small plasmids from halophilic archaebacteria in vivo.

The halophilic archaebacterium Halobacterium strain GRB harbours a multicopy plasmid of 1.7 kb which is negatively supercoiled. After addition of novobiocin to culture medium all 1.7 kb plasmid molecules become positively supercoiled. Positive supercoiling occurs at the same dose of novobiocin inhibiting the eubacterial DNA gyrase in vitro. Novobiocin also induces positive supercoiling of pHV2, a 6.3 kb plasmid from Halobacterium volcanii. These results indicate the existence of a mechanism producing positive superturns in halobacteria. The 1.7 kb plasmid from Halobacterium GRB could be used to produce high amounts of pure positively supercoiled DNA for biophysical and biochemical studies.

DNA, Superhelical↗
PubMed1988

Coumarin and quinolone action in archaebacteria: evidence for the presence of a DNA gyrase-like enzyme.

The action of novobiocin and coumermycin (two coumarins which interact with the gyrB subunit of eubacterial DNA gyrase) and ciprofloxacin (a fluoroquinolone which interacts with the gyrA subunit of DNA gyrase) was tested on several archaebacteria, including five methanogens, two halobacteria, and a thermoacidophile. Most strains were sensitive to doses of coumarins (0.02 to 10 micrograms/ml) which specifically inhibit DNA gyrase in eubacteria. Ciprofloxacin inhibited growth of the haloalkaliphilic strain Natronobacterium gregoryi and of the methanogen Methanosarcina barkeri. In addition, ciprofloxacin partly relieved the sensitivity to coumarins (and vice versa). Novobiocin inhibited DNA replication in Halobacterium halobium rapidly and specifically. Topological analysis has shown that the 1.7-kilobase plasmid from Halobacterium sp. strain GRB is negatively supercoiled; this plasmid was relaxed after novobiocin treatment. These results support the existence in archaebacteria of a coumarin and quinolone target related to eubacterial DNA gyrase.

Aminocoumarins↗
PubMed1987

Antitumor drugs inhibit the growth of halophilic archaebacteria.

Permeability mutants of Escherichia coli have been used to prescreen antitumor drugs. However, most compounds active against eucaryotic proteins have no effect on isofunctional proteins of eubacteria. In contrast, we show that growth of halophilic archaebacteria, procaryotes as distantly related to eubacteria as to eucaryotes, is inhibited by several drugs known to interact with tubulin, actomyosin and DNA topoisomerase II of eucaryotes. Actually, different types of evidence indicate the presence of analogous proteins in halophilic archaebacteria: (a) a yeast actin probe hybridizes with DNA restriction digests of Halobacterium halobium; (b) antibodies against tubulin and actin from chicken react in a crude extract of H. halobium with polypeptides having Mr of 55,000 and 80,000, respectively; (c) the epipodophyllotoxin VP16, a eucaryotic DNA topoisomerase II inhibitor, induces DNA strand breaks with DNA-protein covalent linkage in H. halobium as in eucaryotes. Besides the evolutionary implications, these data indicate that halophilic archaebacteria can be used to prescreen antitumor drugs active on eucaryotic proteins.

Actins↗
PubMed1987

Effects of the antitumor drug VP16 (etoposide) on the archaebacterial Halobacterium GRB 1.7 kb plasmid in vivo.

The topoprofile of 1.7 kb plasmids from the archaebacterium Halobacterium GRB was analysed from cells growing with or without VP16 (etoposide). This drug interferes with the breakage-reunion reaction of eukaryotic DNA topoisomerase II by inhibiting the ligase activity of this enzyme. Addition of VP16 to the culture medium of Halobacterium GRB cells results in the introduction of single- and double-strand DNA breaks in part of the plasmid population, with proteins covalently associated at their 5' ends. While some of the remaining covalently closed circular DNA molecules are relaxed, VP16 treatment also gives rise to the production of positively supercoiled 1.7 kb plasmids. In contrast to adriamycin, VP16 does not intercalate into the 1.7 kb plasmid DNA in vivo. These results suggest that the VP16 target in halobacteria is a DNA topoisomerase II. Three major cleavage sites were detected on the 1.7 kb plasmid after VP16 treatment in vivo.

DNA, Bacterial↗
PubMed1986

beta-Mannosidase in human serum and urine. A comparative study.

All serum and urine beta-mannosidase activities are adsorbed on a DEAE-Trisacryl column at pH 6. Only one form is eluted with a NaCl linear gradient. The two enzymes, isolated from either serum or urine exhibit similar properties. Slight differences are only observed in thermostability and molecular weight.

Adult↗
PubMedDate not supplied

Probing antinuclear antibody specificities by peptide phage display libraries.

OBJECTIVE: To uncover the specificities of autoantibodies to nuclear proteins (ANA) in patients with juvenile rheumatoid arthritis (JRA). METHODS: Peptide ligands for ANA were selected by panning random peptide phage display libraries on antibodies binding to HEp-2 cells. Positive phage clones were identified by the immunoscreening technique. RESULTS: Groups of peptides were identified, some of which share the core motifs of KTTTnPY, RVADnL/I or RnNSPL. Perinuclear and nuclear staining of HEp-2 cells were obtained with patient serum antibodies binding to the phage displaying the core peptide motifs. In contrast, no significant reactivity was seen with the antibodies binding to the wild type phage. Antibodies to the phage displaying peptides containing some of the core motifs were detected more frequently in ANA-positive as compared to ANA-negative JRA patients. Homology search with the selected core motifs revealed a significant homology with a number of human nuclear proteins and proteins from potential infectious agents that could serve as trigger in the breakdown of tolerance. CONCLUSION: Panning of phage display libraries on antibodies reacting with cellular structures can lead to the identification of their specificities. Thus, the peptide epitopes reported here constitute additional information that may lead to the development of diagnostic tests and the identification of the parental antigens that initiated the B cell responses in patients with JRA.

Amino Acid Sequence↗
PubMedDate not supplied

T cell receptor variable region gene usage in juvenile chronic arthritis.

Up to now the data regarding T cell receptor V-gene usage by juvenile chronic arthritis synovial T lymphocytes has been conflicting. Thus, some studies claim that locally in the diseased joint there is an oligoclonal expansion of T cells with restricted T cell receptor variable region gene usage while others have found V-gene usage in the joint compatible with a polyclonal expansion of the T cells.

Arthritis, Juvenile↗
PubMedDate not supplied

Antibody epitopes probed by immunoselected phage-display library peptides in members of a family with various rheumatic manifestations.

OBJECTIVE: The random peptide combinatorial phage library approach overcomes the problem of lack of structural information about the aetiological agent or the antigen responsible for a given disease. Here, we used such a strategy to gain insight into the aetiology of rheumatoid arthritis (RA). METHODS: We analyzed the reactivity of serum antibodies from a family with various rheumatic manifestations against RA-immunoselected nanopeptides displayed on phage particles. RESULTS AND CONCLUSION: We found that within the same family, there was a difference in antibody reactivity against the peptides tested. The IgG isotype of the peptide reactive antibodies indicated that the observed reactivities were not related to the presence of polyreactive IgM antibodies. Furthermore, it is unlikely that the observed reactivity was due to rheumatoid factors (RF), since two patients who were positive for the immunoselected Pep3 peptide (LSSREPQAR) were RF negative. We also found that the serum of one patient with polyarthralgias also reacted with the same peptide bound by the RA serum, which may suggest the implication of a common aetiological agent in the apparition of this antibody reactivity. Finally, we noted that one patient with Sjögren's syndrome had antibodies to the RA peptide, which may indicate a potential relationship between these two autoimmune diseases.

Arthritis, Rheumatoid↗
PubMedDate not supplied

Analysis of the NF-kappa B p65 subunit, Fas antigen, Fas ligand and Bcl-2-related proteins in the synovium of RA and polyarticular JRA.

OBJECTIVE: To investigate the nuclear localization of the transcription factor NF-kappa B, the status of apoptosis and the expression of the Fas antigen, Fas ligand, Bcl-2, Bcl-xL and Bax by synovial cells. METHODS: Electrophoresis mobility shift assay (EMSA), immunohistochemical staining, two colour-flow cytometry and the terminal deoxynucleotidyl transferase (TDT)-mediated dUTP nick end labelling (TUNEL)-technique were used. RESULTS: The NF-kappa B p65 subunit appears to be present in the nuclei of synovial tissue and fluid cells as detected by EMSA and immunohistochemical staining. Fas antigen and Fas ligand (L) are expressed on up to 90% and 11% of CD3+ synovial fluid (SF) cells, respectively. Both the Fas antigen and its ligand are also expressed by synovial tissue cells. Interestingly, freshly isolated SF T cells upregulated the expression of Bcl-xL as compared to Bcl-2. An overexpression of Bax compared to Bcl-xL was seen in the synovial tissues (ST) of patients with ongoing apoptosis, but not in patients with few apoptotic cells. CONCLUSIONS: NF-kappa B appear to be activated in vivo, both Fas and its ligand being expressed by synovial cells. Apoptosis is ongoing in the ST with significant patient variations. Such variations could be in part due to the level of Bax expression. Finally, the upregulation of Bcl-xL expression may contribute to the accumulation of SF infiltrating T cells.

Adolescent↗