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At least 253 records · Page 14Linked to original sources
PubMed1997

Genetic recombinations between c-myc and Igh mu as precursors for recombinations between c-myc and Igh alpha in BALB/c plasmacytomas.

In this paper we present evidence that primary plasmacytomas harboring a balanced chromosomal translocation t(12;15) may consist of a mosaic of neoplastic clones of tumor cells, in which some of the clones are derived from common progenitors by large additional deletions which alter or "remodel" the fine structure of the t(12;15) on the c-myc-deregulating chromosome. This finding is based on the molecular analysis of the t(12;15) in three plasmacytomas, TEPC 1194, PCT 4127 and PCT 4132, in which primary clones of tumor cells with recombinations between the Ig heavy-chain (Igh) mu locus (Igh mu) and c-myc were found to be related to secondary clones of tumor cells with recombinations between the Igh alpha locus (Igh alpha) and c-myc. Clonal relatedness was based on unique junction fragments between S mu and c-myc that were found to be identical in Igh mu/c-myc and Igh alpha/c-myc breakpoint regions. S mu/c-myc breakpoints with adjoining sequences can thus be used as clonotypic markers, providing molecular fingerprints for the evolution of precursor cells with Igh mu/c-myc recombinations into progenitor cells with Igh alpha/c-myc recombinations. We propose that aberrant isotype switch recombination or illegitimate rearrangement in switch regions converts Igh mu/c-myc rearrangements, which are found very rarely in established plasmacytomas, into Igh alpha/c-myc rearrangements, which are present in about 80% of plasmacytomas with t(12;15). Remodeling of the t(12;15) results in closer juxtaposition of c-myc to the 3'-C alpha locus control region and probably in enhanced transcription of c-myc. We suggest that remodeling of c-myc-deregulating rearrangements constitutes a novel progression mechanism in malignant B-cell development.

Animals↗
PubMed2001

Effect of interfering substances on current response of recombinant peroxidase and glucose oxidase-recombinant peroxidase modified graphite electrodes.

Graphite electrodes have been modified with different forms of horseradish peroxidase (HRP). These included native HRP, wild-type recombinant HRP, and two single-point recombinant HRP mutants, N70V and N70D. The mediator-less response of these electrodes to H2O2 was studied indicating that electrodes modified with recombinant HRP forms are more stable than those modified with native HRP. Various interfering compounds were investigated for their effect on the current response to H2O2. It was found that interferences such as acetaminophen and dopamine affected the response by mediating the electron transfer (ET) between graphite and peroxidases. The mediating behaviour manifested itself as an increased current of the electrode to H2O2. The interfering effect was less pronounced for the electrodes modified with recombinant HRPs possessing better electronic coupling with the graphite surface. The interfering behaviour of acetaminophen on the response for glucose with the bienzyme electrode containing co-immobilised glucose oxidase and HRP was mainly ascribed to mediation of ET between graphite and HRP. It was experimentally proven that a high efficiency of direct ET between graphite and recombinant HRP substantially reduces the interfering effect of acetaminophen.

Journal Article↗
PubMed1997

No effect of a new second-generation B-domain-deleted recombinant product on lymphocyte transformation in vitro: a study of plasma-derived and recombinant products.

Immunomodulatory effects of various factor VIII and factor IX clotting factor concentrates (CFCs) and of albumin were evaluated by a sensitive assay measuring the incorporation of 3H-thymidine in phytohaemagglutinin-stimulated lymphocytes in the presence of monodansylthiacadaverine. In contrast to previous findings by others, we found lymphocyte transformation to be inhibited by all plasma-derived factor VIII concentrates at concentrations of 0.02, 0.2 and 2.0 IU/ml, including those purified by monoclonal antibodies (P < 0.05). Kryobulin TIM3 had the most pronounced effect. In addition, three plasma-derived human albumin preparations exerted a similar inhibitory effect as the factor VIII concentrates, whereas the corresponding plasma-derived factor IX concentrates only manifested minor immunomodulatory effects. Of the recombinant preparations, only Recombinate exerted an inhibitory effect at 0.02 and 0.2 IU/ml, whereas both Kogenate and Recombinate decreased 3H-thymidine incorporation at 2.0 IU/ml (P = 0.01). No immunomodulatory effect at all was observed with r-VIII SQ, a new B-domain-deleted recombinant factor VIII preparation free from added albumin. The significance of this finding regarding immunological side-effects including inhibitor development remains to be evaluated, but this second-generation recombinant product opens up new and interesting perspectives yet to be explored.

Cadaverine↗
PubMed1995

Highly attenuated HIV type 2 recombinant poxviruses, but not HIV-2 recombinant Salmonella vaccines, induce long-lasting protection in rhesus macaques.

Immunization schemes employing priming with vector-based vaccine candidates followed by subunit booster administrations have been explored and shown to have merit in the human immunodeficiency virus type 1 (HIV-1) and simian immunodeficiency virus systems. In this study, we have assessed the priming capacity of highly attenuated poxvirus vector (NYVAC and ALVAC)-based HIV-2 recombinants, as well as Salmonella typhimurium HIV-2 recombinants in rhesus macaques. ALVAC- and NYVAC-based vaccine candidates expressing the HIV-2 gag, pol, and env genes or NYVAC-based recombinants expressing either gp160 or gp120 were used to immunize rhesus macaques in combination protocols with alum-adjuvanted HIV-2 rgp160. Following intravenous challenge exposure with 100 infectious doses of the HIV-2SBL6669 parental virus genotype mixture, seven of eight animals were protected from infection. The seven protected animals were rechallenged 6 months postprimary challenge, without additional booster inoculations, with the same dose of the HIV-2SBL6669 parental virus. Five of the seven animals remained protected against HIV-2 infection at 6 months following the second challenge. In contrast, oral immunization with recombinant Salmonella expressing the HIV-2 gag and the gp120 portion of the envelope either alone or in combination with alum-adjuvanted rgp160 failed to confer protection. These results suggest that the NYVAC- and ALVAC-based recombinants may confer long-lasting protection and that these two highly attenuated poxvirus vaccine vectors may represent promising candidates for developing an acquired immunodeficiency syndrome vaccine.

Amino Acid Sequence↗
PubMed2004

Inhibitor development in patients receiving recombinant factor VIII (Recombinate rAHF/Bioclate): a prospective pharmacovigilance study.

Clinical trials to date have not been adequately powered to assess comparatively infrequent events such as inhibitor development in previously treated patients (PTPs). Comprehensive large-scale pharmacovigilance studies can be useful for this purpose. We prospectively collected inhibitor development reports worldwide among recipients of Recombinate rAHF recombinant factor VIII (rFVIII), also formerly distributed under the product name Bioclate, for the entire postlicensure period from 1993 through 2002. To determine level of exposure to rFVIII we also compiled the Recombinate rAHF/Bioclate International Units (IU) distributed annually. To estimate inhibitor incidence separately for previously untreated or minimally treated patients (PUPs) with 1-50 exposure days and PTPs with >50 exposure days, we used haemophilia A incidence and prevalence data and pooled mean annual rFVIII consumption per PUP and PTP from international multicentre prospective clinical trials. Documented inhibitor cases totalled 89, and the total quantity of Recombinate rAHF/Bioclate rFVIII distributed was 6.48 x10(9) IU. No lot association or other clustering of inhibitor events was evident in PTPs. The incidence of all reported inhibitors, expressed as a percentage of patients treated, was 11.9% (CI: 5.05-28.0%) for PUPs when compared with 0.123% (CI: 0.030-0.512%) for PTPs. The rates for high-titre inhibitors (>5 BU) only were 5.96% (CI: 3.00-11.8%) for PUPs and 0.0554% (CI: 0.0113-0.271%) for PTPs. Thus, incidence rates for both all inhibitors and high-titre inhibitors in PTPs were 1% of the corresponding rates in PUPs. Data from prospective PUP clinical trials involving intensive active monitoring suggest that true inhibitor incidence may be approximately twice that estimated in this pharmacovigilance study. Nevertheless, inhibitor development in PTPs receiving Recombinate rAHF/Bioclate is infrequent.

Adolescent↗
PubMed1970

Molecular Recombination in T4 Bacteriophage Deoxyribonucleic Acid: III. Formation of Long Single Strands During Recombination.

Evidence was presented to support the hypothesis that long single strands appearing at late times (15 min after infection) are produced as a result of recombination and not as a continuous elongation during the replication process. The production of long strands does not depend on the multiplicity of infection, and the first long strands appear at the time when 20 to 50 phage equivalent units of deoxyribonucleic (DNA) are synthesized, and not earlier. The addition of chloramphenicol at 5 min, which prevents molecular recombination but allows replication of DNA, prevents the formation of long, single strands. Chloramphenicol added between 8 and 10 min after infection, a time at which molecular recombination is fully expressed and covalent repair of recombinant molecules is allowed, does not prevent formation of long single strands. Cutting of single-strand DNA with a limited amount of endonuclease I allows confirmation that the fast-sedimenting characteristic of intracellular denatured DNA is caused primarily by the length of the strands, and not by the formation of aggregates. The computer simulation of two recombination models indicates the feasibility of random breakage and rejoining of molecules in generating long concatenates.

Journal Article↗
PubMed2002

The recombinant T cell receptor strategy: insights into structure and function of recombinant immunoreceptors on the way towards an optimal receptor design for cellular immunotherapy.

A promising approach in adoptive immunotherapy is based on the induction of a specific cellular anti-tumor response by antigen-specific, cytolytic T cells. Due to difficulties in isolating tumor-specific T cells in sufficient amounts, it was proposed to graft cytolytic T cells with an antigen-specific, recombinant T cell receptor. The antigen binding domain of the receptor consists of a single-chain antibody fragment (scFv) that is derived from a monoclonal antibody and binds to a tumor associated antigen. The intracellular signalling domain is derived from the cytoplasmic part of a membrane bound receptor to induce cellular activation, e.g., the Fc epsilon RI receptor gamma-chain or the CD3 zeta-chain. By use of this type of recombinant receptor, the strategy combines the advantages of MHC-independent, antibody-based antigen binding with efficient T cell activation upon specific binding to the receptor ligand. The modular composition of the receptor, moreover, facilitates modification of both the antigen binding and signalling properties. Accordingly, we and others have generated a panel of recombinant T cell receptors with specificities for malignantly or virally transformed cells. Receptor grafted effector cells were demonstrated to mediate a highly efficient immune response towards antigen expressing target cells. However, little is known about the impact of the recombinant receptor modules on recognition of highly heterologous target antigens and on cellular activation in a complex immunological context. This review summarizes the current knowledge about the generation and function of recombinant immunoreceptors and discusses the limitations and perspectives of the methodology for use in cellular immunotherapy.

Animals↗
PubMed1984

Mechanism of illegitimate recombination: common sites for recombination and cleavage mediated by E. coli DNA gyrase.

Illegitimate recombination dependent on DNA gyrase in a cell-free system has previously been described. We have now mapped DNA gyrase cleavage sites in the vicinity of known recombination sites in pBR322. Among five recombination sites examined, three were found to coincide with a DNA gyrase cleavage site. This result suggests that the cleavage of DNA by DNA gyrase has a central role in the recombination process.

Base Sequence↗
PubMed1983

Proof of recombination between viral and cellular genomes in human KB cells productively infected by adenovirus type 12: structure of the junction site in a symmetric recombinant (SYREC).

In previous work we have described a symmetric recombinant (SYREC1) between Ad12 DNA and human KB cell DNA. This recombinant DNA molecule has been generated during productive infection and is encapsidated into virions. From the DNA of a similar symmetric recombinant (termed SYREC2) between the left terminus of Ad12 DNA and human KB cellular DNA, the site of linkage between the two DNAs was cloned and sequenced. It was demonstrated that the first 2081 Ad12 nucleotides counting from the left viral terminus are conserved and linked to a sequence of GC-rich (70.4% G + C) KB cell DNA which occurs about 20 times per cellular genome. Except for a common 5'-CTGGC-3' pentanucleotide between the Ad12 DNA and KB cell DNA sequences, extensive patch homologies were not apparent at the site of junction. Similarly, comparisons of the deleted Ad12 DNA sequence and the cellular sequence replacing it did not reveal patch homologies. The 304 bp abutting the Ad12 terminus were shown to hybridize to KB cell DNA. These results provided definitive proof for the occurrence of recombinants between viral and cellular DNAs in human cells productively infected by Ad12 as previously shown by less direct experiments (Burger and Doerfler, 1974; Schick et al., 1976). Across the site of junction, an open reading frame exists which extends the truncated 54-kDal protein of the E1b region of Ad12 DNA for another 66 amino acids encoded by KB cellular DNA. This sequence is terminated by two UGA translational termination signals. The hypothetical protein has not yet been isolated.

Adenoviridae↗
PubMed2003

Extrachromosomal recombination substrates recapitulate beyond 12/23 restricted VDJ recombination in nonlymphoid cells.

V(D)J recombination occurs efficiently only between gene segments flanked by recombination signals (RSs) containing 12 and 23 base pair spacers (the 12/23 rule). A further limitation "beyond the 12/23 rule" (B12/23) exists at the TCRbeta locus and ensures Dbeta usage. Herein, we show that extrachromosomal V(D)J recombination substrates recapitulate B12/23 restriction in nonlymphoid cells. We further demonstrate that the Vbeta coding flank, the 12-RS heptamer/nonamer, and the 23-RS spacer each can significantly influence B12/23 restriction. Finally, purified core RAG1 and RAG2 proteins (together with HMG2) also reproduce B12/23 restriction in a cell-free system. Our findings indicate that B12/23 restriction of V(D)J recombination is cemented at the level of interactions between the RAG proteins and TCRbeta RS sequences.

Animals↗
PubMed2001

Links between replication and recombination in Saccharomyces cerevisiae: a hypersensitive requirement for homologous recombination in the absence of Rad27 activity.

The RAD27 gene of Saccharomyces cerevisiae encodes a 5'-3' flap exo/endonuclease, which plays an important role during DNA replication for Okazaki fragment maturation. Genetic studies have shown that RAD27 is not essential for growth, although rad27 Delta mutants are temperature sensitive. Moreover, they exhibit increased sensitivity to alkylating agents, enhanced spontaneous recombination, and repetitive DNA instability. The conditional lethality conferred by the rad27 Delta mutation indicates that other nuclease(s) can compensate for the absence of Rad27. Indeed, biochemical and genetical analyses indicate that Okazaki fragment processing can be assured by other enzymatic activities or by alternative pathways such as homologous recombination. Here we present the results of a screen that makes use of a synthetic lethality assay to identify functions required for the survival of rad27 Delta strains. Altogether, we confirm that all genes of the Rad52 recombinational repair pathway are required for the survival of rad27 Delta strains at both permissive (23 degrees C) and semipermissive (30 degrees C) temperatures for growth. We also find that several point mutations that confer weaker phenotypes in mitotic than in meiotic cells (rad50S, mre11s) and additional gene deletions (com1/sae2, srs2) exhibit synthetic lethality with rad27 Delta and that rad59 Delta exhibits synergistic effects with rad27 Delta. This and previous studies indicate that homologous recombination is the primary, but not only, pathway that functions to bypass the replication defects that arise in the absence of the Rad27 protein.

Alleles↗
PubMed1999

Saturation mutagenesis of the E. coli RecA loop L2 homologous DNA pairing region reveals residues essential for recombination and recombinational repair.

The disordered mobile loop L2 of the Escherichia coli RecA protein is known to play a central role in DNA binding and pairing. To investigate the local chemical environment in relation to function we performed saturation mutagenesis of the loop L2 region (amino acid positions 193-212) using a site-directed mutagenesis procedure, and determined the recombinational proficiency of the 380 mutants using genetic assays for homologous recombination and recombinational repair. Residues Asn193, Gln194, Arg196, Glu207, Thr209, Gly211, and Gly212 were identified as stringently required for recombinational events in bacterial cells. In addition, our findings suggest the involvement of loop L2 in the ATPase activity of RecA, and a role for residues Gln194, Arg196, Lys198 and Thr209 in the DNA-dependent hydrolysis of ATP. Finally, since 20 residue peptides that comprise this region can pair homologous DNAs by forming filamentous beta-structures, we propose how the information from the mutant analysis might facilitate the use of a simplified amino acid alphabet to design beta-structure forming L2 peptides with improved RecA-like activities.

DNA Repair↗
PubMed1994

Non-recombinant background in gene targeting: illegitimate recombination between a hpt gene and a defective 5' deleted nptII gene can restore a Kmr phenotype in tobacco.

Previously we have demonstrated gene targeting in plants after Agrobacterium-mediated transformation. In these initial experiments a transgenic tobacco line 104 containing a T-DNA insertion with a defective neomycin phosphotransferase (nptII) gene was transformed with a repair construct containing an otherwise defective nptII gene. Homologous recombination between the chromosomally located target and the incoming complementary defective nptII construct generated an intact nptII gene and led to a kanamycin-resistant (Kmr) phenotype. The gene targeting frequency was 1 x 10(-5). In order to compare direct gene transfer and Agrobacterium-mediated transformation with respect to gene targeting we transformed the same transgenic tobacco line 104 via electroporation. A total of 1.35 x 10(8) protoplasts were transformed with the repair construct. Out of nearly 221,000 transformed cells 477 Kmr calli were selected. Screening the Kmr calli via PCR for recombination events revealed that in none of these calli gene targeting had occurred. To establish the origin of the high number of Kmr calli in which gene targeting had not occurred we analysed plants regenerated from 24 Kmr calli via PCR and sequence analysis. This revealed that in 21 out of 24 plants analysed the 5'-deleted nptII gene was fused to the hygromycin phosphotransferase (hpt) gene that was also present on the repair construct. Sequence analysis of 7 hpt/nptII gene fusions showed that they all contained a continuous open reading frame. The absence of significant homology at the fusion site indicated that fusion occurred via a process of illegitimate recombination. Therefore, illegitimate recombination between an introduced defective gene and another gene present on the repair construct or the chromosome has to be taken into account as a standard byproduct in gene targeting experiments.

Amino Acid Sequence↗
PubMed1976

Genetic recombination of Coprinus. V. Repair synthesis of deoxyribonucleic acid and its relation to meiotic recombination.

Repair synthesis of DNA per se at pachytene is not needed for commitment to meiotic recombination although it is a necessary event to follow. Recombination frequency is governed by the rate of nicking and the time in which unrepaired nicks are allowed to match and crossover. Cold treatment at pachytene prevented repair synthesis, hence open nicks were accumulated to match and crossover, and a 3-fold increase in recombination resulted. The kinetics of cold temperature effect followed a quadratic function as shown by a computer simulation which agreed with our experimental data (Lu, 1974b). High temperature did not change the rate of repair synthesis. It did cause an increased nicking which led to a twofold increase in recombination and which entailed a higher rate of recovery repair synthesis.

Agaricales↗
PubMed1990

The recombinational hot spot mutation ade6-M26 of Schizosaccharomyces pombe stimulates recombination at sites in a nearby interval.

With the help of in vitro constructed intragenic double mutants, we investigated the influence of the recombinational hot spot mutation ade6-M26 on meiotic recombination between two additional ade6 mutations proximal to it. Recombination was stimulated four-fold when M26 was present in a heterozygous condition and ten-fold when homozygous. M26 itself remained unaffected in a substantial number of these events. This indicates that the stimulation can not only be due to a preferred conversion of M26 to wild-type with co-conversion of the second mutation in cis. A model is proposed in which M26 acts as an "entry site" for recombinational enzymes.

Chromosome Mapping↗
PubMed1987

Illegitimate recombination in Bacillus subtilis: nucleotide sequences at recombinant DNA junctions.

The illegitimate integration of plasmid pGG20 (the hybrid between Staphylococcus aureus plasmid pE194 and Escherichia coli plasmid pBR322) into the Bacillus subtilis chromosome was studied. It was found that nucleotide sequences of both parental plasmids could be involved in this process. The recombinant DNA junctions between plasmid pGG20 and the chromosome were cloned and their nucleotide sequences were determined. The site of recombination located on the pBR322 moiety carried a short region (8 bp) homologous with the site on the chromosome. The nucleotide sequences of the pE194 recombination sites did not share homology with chromosomal sequences involved in the integration process. Two different pathways of illegitimate recombination in B. subtilis are suggested.

Bacillus subtilis↗
PubMed1986

Illegitimate recombination mediated by T4 DNA topoisomerase in vitro. Recombinants between phage and plasmid DNA molecules.

Illegitimate recombination dependent on T4 DNA topoisomerase in a cell-free system has recently been described. In that work, recombinants between two phage lambda DNA molecules were produced by the topoisomerase alone, without an Escherichia coli extract. In this paper, it is shown that recombination between phage lambda and circular plasmid DNA molecules can also be detected in the presence or absence of an E. coli extract but at frequencies two or three orders of magnitude lower than that observed in the phage-phage cross. The frequency is probably lower because multiple recombination is required in the case of the phage-plasmid cross.

Base Sequence↗
PubMed1980

Time of recombination in the Drosophila melanogaster oocyte. II. Electron microscopic and genetic studies of a temperature-sensitive recombination mutant.

A test has been carried out to determine if the restrictive temperature (31 degrees) acts to reduce recombination in the temperature-sensitive recombination-deficient genotype rec-l26/rec-l16 by reducing or eliminating the synaptonemal complex. Measurements of the length of synaptonemal complexes in heat-treated and untreated stage 1 oocytes, following termination of the temperature-sensitive period, reveal less than a 5% difference, with the greater length present in the treated oocytes. Alterations are not observed in synaptonemal complex distribution within the nucleus or in its fine structure. Parallel genetic studies confirm earlier observations that the restrictive temperature, whose action is confined to a 36-h sensitive period virtually coextensive with premeiotic-S, drastically reduces recombination to approximately 10% of normal. The results are most simply interpreted to mean that the restrictive temperatures acts directly on the recombination process.

Animals↗