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T Lindahl

Publications and source records attributed to T Lindahl.

At least 163 records · Page 9Linked to original sources
PubMed1979

Sites of sequence variability in Epstein-Barr virus DNA from different sources.

The intracellular Epstein-Barr virus (EBV) DNA present in virus-transformed cells was partly purified from 23 cell lines or biopsies of Burkitt lymphoma, nasopharyngeal carcinoma, infectious mononucleosis, or healthy carrier origin. Such DNA was cleaved in fragments (A-K) of molecular weights between 1 x 10(6) and 30 x 10(6) with restriction enzyme EcoRI, and these fragments were analyzed by standard methods involving agarose gel electrophoresis, transfer to nitrocellulose filters, and hybridization with radioactive EBV DNA or complementary RNA. Sequence variability among different EBV DNA isolates was largely confined to the A, C, and I fragments. These results are discussed in relation to the linkage map of the EcoRI fragments of EBV DNA. The EcoRI cleavage pattern of intracellular viral DNA of an EBV-like virus from baboon cells, Herpesvirus papio, was entirely different from that of human EBV isolates.

Animals↗
PubMed1979

Size of the intracellular circular Epstein-Barr virus DNA molecules in infectious mononucleosis-derived human lymphoid cell lines.

The size of non-integrated circular Epstein-Barr virus (EBV) DNA molecules isolated from seven different human lymphoblastoid cell lines of infectious mononucleosis origin has been determined by sedimentation analysis and by direct contour length measurements on electron micrographs. Six lines had intracellular circular EBV genomes of the same size as linear virion DNA molecules. The seventh line, established with the B95-8 strain of EBV, was the only one found to have circular EBV DNA molecules significantly smaller than virion DNA. The data show that intracellular EBV DNA circles of reduced size do not generally occur in infectious mononucleosis-derived cell lines.

Base Sequence↗
PubMed1978

Enzymatic excision of free hypoxanthine from polydeoxynucleotides and DNA containing deoxyinosine monophosphate residues.

A DNA glycosylase that releases free hypoxanthine by selective cleavage of dIMP residues in polydeoxynucleotides and DNA containing this nonconventional nucleotide is present in Escherichia coli cell extracts. The partly purified enzyme, termed hypoxanthine-DNA glycosylase, does not require divalent cations or phosphate for activity, and it acts more efficiently on double-stranded than on single-stranded substrates. The enzyme has properties different from either uracil-DNA glycosylase or 3-methyladenine-DNA glycosylase and is present at normal levels in E. coli mutants deficient in either of the latter two DNA glycosylases.

Bacillus subtilis↗
PubMed1978

Properties of 3-methyladenine-DNA glycosylase from Escherichia coli.

An Escherichia coli enzyme that releases 3-methyladenine and 3-ethyladenine in free form from alkylated DNA has been purified 2800-fold in 7% yield. The enzyme does not liberate several other alkylation products from DNA, including 7-methylguanine,O6-methylguanine, 7-methyladenine, N6-methyladenine, 7-ethylguanine, O6-ethylguanine, and the arylalkylated purine derivatives obtained by treatment of DNA with 7-bromomethyl-12-methylbenz[a]anthracene. The reaction of the enzyme with alkylated DNA leads to the introduction of apurinic sites but no chain breaks (less than one incision per ten apurinic sites), and there is no detectable nuclease activity with native DNA, depurinated DNA, ultraviolet-irradiated DNA, or X-irradiated DNA as potential substrates. The enzyme is termed 3-methyladenine-DNA glycosylase. It is a small protein, Mr = 19 000, that does not require divalent metal ions, phosphate, or other cofactors in order to cleave base-sugar bonds in alkylated DNA.

Adenine↗
PubMed1978

State of Epstein-Barr virus DNA in an American Burkitt's lymphoma line.

A human lymphoma cell line, positive for the Epstein-Barr virus (EBV)-associated nuclear antigen, was recently established from a North American Burkitt's lymphoma. This cell line, SU-AmB-2, contained EBV DNA both in the form of circular, nonintegrated DNA molecules of viral genome length, present in multiple copies per cell, and as integrated sequences. Having DNA present in both of these forms, it resembled cell lines established from African Burkitt's lymphomas. In studies on EBV strain differences, the episomal viral DNA in Burkitt's lymphoma cells may now be compared with viral DNA in nonmalignant cells with the use of cell lines from Burkitt's lymphoma patients of similar geographic origin.

Africa, Eastern↗
PubMed1978

Integrated viral DNA sequences in Epstein-Barr virus-converted human lymphoma lines.

Most human lymphoid cell lines contain multiple copies of circular, nonintegrated Epstein-Barr virus (EBV) DNA molecules as well as viral DNA sequences with properties of integrated DNA. The physical state of the EBV DNA in a human lymphoma line that only contains one virus genome equivalent per cell has now been studied by three different methods, neutral CsCl density gradient centrifugation, actinomycin D-CsCl gradient centrifugation, and Hirt fractionation. This cell line, AW-Ramos, has been obtained by EBV infection in vitro of the apparently EBV-negative Ramos lymphoma line. The results indicate that the EBV DNA in AW-Ramos is present exclusively in a linearly integrated form. Similar data were obtained with two other EBV-converted sublines of Ramos cells.

Base Sequence↗
PubMed1978

Purification of the Epstein-Barr virus-determined nuclear antigen from Epstein-Barr virus-transformed human lymphoid cell lines.

The Epstein-Barr virus-determined nuclear antigen (EBNA) was purified from extracts of the human lymphoid cell lines Raji, Namalwa, and B95-8/MLD by two different methods. In the first approach, the apparently native antigen was purified 1,200-fold by a four-step procedure involving DNA-cellulose chromatography, blue dexptran-agarose chromatography, hydroxyapatite chromatography, and gel filtration, employing complement fixation as the assay procedure. Such EBNA preparations specifically inhibited the anticomplement immunofluorescence test for EBNA and bound to methanol/acetic acid-fixed metaphase chromosomes. The purified antigen, which has a molecular weight of 170,000 to 200,000, yielded a single protein band of molecular weight about 48,000 by sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis. These data indicate that native EBNA has a tetrameric structure. In the second purification method, EBNA-containing cell extracts containing radioactively labeled proteins were incubated with anti-EBNA-positive sera, and antigen-antibody complexes were adsorbed to matrix-bound staphylococcal protein A. The bound proteins were then released with an SDS-containing buffer, and denatured EBNA was separated from antibody chains by SDS-polyacrylamide gel electrophoresis and visualized by fluorography. The denatured EBNA obtained in radiochemically pure form by this procedure has a molecular weight of about 48,000, so both methods yield an EBNA monomer of the same size.

Antigens, Viral↗
PubMed1978

Integration of Epstein-Barr virus DNA.

The application to herpesviruses of different standard methods fo measuring tumour-virus integration is discussed. The evidence for the presence of integrated virus DNA in EBV-transformed cells is summarized.

Cell Transformation, Neoplastic↗
PubMed1978

Herpesvirus papio: state of viral DNA in baboon lymphoblastoid cell lines.

Baboon lymphoblastoid cell lines (LCL) transformed with herpesvirus papio were evaluated for the state of HVP DNA in the cells by caesium chloride density-gradient centrifugation and DNA-cRNA filter hybridization. Five HVP producer cultures and one non-producer culture were studied and non-integrated and integrated HVP DNA were detected in all producer cultures whereas only integrated HVP DNA could be demonstrated in the non-producer LCL. Non-integrated HVP dna had a density of 1.715--1.716 g/cm3 in caesium chloride corresponding to a guanine + cytosine content of 56--57%.

Animals↗
PubMed1977

Human lymphoblastoid cell lines derived from individuals without lymphoproliferative disease contain the same latent forms of Epstein-Barr virus DNA as those found in tumor cells.

The physical state of the intracellular Epstein-Barr virus DNA was characterized in four human lymphoblastoid cell lines, F-265, NC-37, U-303 L, and PG-1, derived from individuals without lymphoproliferative disease. For comparison, a previously investigated Burkitt lymphoma line, Raji, and a more recently established cell line of that origin, Rael, were also studied. The techniques employed were CsCl density gradient centrifugation, glycerol gradient centrifugation, and ethidium bromide-CsCl density gradient centrifugation in combination with nucleic acid hybridization, as well as electron microscopy contour length measurements of purified circular EBV DNA. All six cell lines contained multiple copies of covalently closed circular EBV DNA-molecules of the same size, as well as viral DNA with the properties of integrated DNA. No differences could be detected between the forms of EBV DNA present in cell lines derived from non-malignant sources and those present in lymphoma lines.

Burkitt Lymphoma↗
PubMed1977

Identification of a purified complement-fixing antigen as the Epstein-Barr-virus determined nuclear antigen (EBNA) by its binding to metaphase chromosomes.

A soluble complement-fixing antigen carried by Epstein-Barr virus (EBV)-transformed human cells has been previously extracted from cell nuclei and purified by DNA-cellulose chromatography [Luka, J., Siegert, W. & Klein, G. (1977) J. Virol., in press]. On addition of this antigen to methanol/acetic acid-fixed metaphase chrmosomes, followed by exposure to human sera containing antibodies against the EBV-determined nuclear antigen (EBNA), brilliant positive staining was obtained by anti-complement immunofluorescence. There was no staining after exposure to EBV-negative sera. Moreover, a nuclear protein fraction, prepared from an EBV-negative cell line in an analogous fashion, failed to induce the staining reaction. These data identify the soluble purified antigen as the EBV-determined nuclear antigen. The purified antigen has a molecular weight of 174,000 +/- 15,000, as determined by sucrose gradient centrifugation and gel filtration experiments. In neutral buffers containing 0.5-1.0 M NaCl, the antigen dissociates into a form of approximately one-half the original molecular weight with retained complement-fixing activity. This "monomer" has a molecular weight of 98,000 +/- 8,000.

Antigens, Viral↗
PubMed1977

Relation between Escherichia coli endonucleases specific for apurinic sites in DNA and exonuclease III.

Contradictory data have recently been published from two different laboratories on the presence vs absence of an intrinsic endonucliolytic activity of E. coli exonuclease III at apurinic sites in double-stranded DNA. It is shown here that an endonuclease activity of this specificity co-chromatographs exactly with exonuclease III on phosphocellulose and Sephadex G-75 columns, indicating that the endonuclease and exonuclease activities are due to the same enzyme. In addition, another E. coli endonuclease specific for apurinic sites exists, which can be separated from exonuclease III by the same chromatographic procedures.

Apurinic Acid↗
PubMed1977

Circular Epstein-Barr virus genomes of reduced size in a human lymphoid cell line of infectious mononucleosis origin.

Circular Epstein-Barr virus (EBV) DNA molecules have been purified and characterized from a human lymphoid cell line derived from a case of heterophile antibody-positive, blood transfusion-induced infectious mononucleosis, 883L. The circular EBV DNA in three cell lines obtained by transformation of human umbilical cord blood leukocytes with a strain of EBV originally derived from 883L was also studied. As estimated from sedimentation velocity data and electron microscopy, the circular EBV DNA molecules are 10 to 15% smaller than either the circular EBV DNA previously found intracellularly in several other types of EBV-transformed cells or the linear EBV DNA present extracellularly in virus particles. In addition, the EBV-transformed cord blood cell lines studied here differed from other EBV-transformed cells in that integrated virus DNA sequences could not be detected.

Burkitt Lymphoma↗