Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.1.30.2 (endonuclease)
18,621 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The analysis of H-2K products from spontaneously generated major histocompatibility complex (MHC) mutants and of the primary structure of other class I antigens suggests the genetic hypothesis that diversity in the MHC results from a copy mechanism analogous to gene conversion. The hypothesis was tested by making precise structural predictions about three partially characterized MHC mutants (bm1, bm3, and bm8). The predictions were based on consensus sequences among class I genes that differ from H-2Kb in the same region of the molecule as do the Kb mutants. In two cases (bm3 and bm8) we successfully predicted the correct amino acid substitution at positions known to be altered but for which the specific nature of the substitution had not been determined. In two additional cases (bm1 and bm8) we predicted and found both new mutation sites and the specific amino acid substitutions. The positions and identifications of the variant amino acids were determined by radiolabeled amino acid sequence analysis and DNA restriction endonuclease analysis. The interaction of MHC genes through a copy mechanism to generate diversity permits the introduction of multiple nucleotide base substitutions into class I sequences by a single genetic event. Such a mechanism may account in part for the large structural divergence among alleles of MHC loci and the high degree of MHC polymorphism among wild mice.
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PMID:Spontaneous H-2 mutants provide evidence that a copy mechanism analogous to gene conversion generates polymorphism in the major histocompatibility complex. 657 97

Although systemic lupus erythematosus (SLE) is known to be positively associated with certain major histocompatibility complex (MHC) class I and/or class II antigens, it is not clear whether the MHC genes are the predisposing genes of the disease rather than markers for other closely linked gene(s). Because of the involvement of tumor necrosis factor (TNF) in the inflammation process and localization of the TNF genes in the proximity of the HLA-B locus, we studied the restriction fragment length polymorphism (RFLP) of the TNF-alpha and -beta genes in 20 SLE patients and 23 normal individuals using restriction endonuclease NcoI. The frequency of a 5.5 kb NcoI fragment from SLE patients was significantly higher than that from normal controls. This result suggests that the polymorphic TNF genes may be involved in the pathogenesis of SLE.
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PMID:Restriction fragment length polymorphism (RFLP) analysis in the TNF genes of patients with systemic lupus erythematosus (SLE). 790 14

The order and recombination fractions (theta) between the bovine major histocompatibility complex DRB3, DYA, and prolactin (PRL) genes were determined by typing of 254 sperm from a triply heterozygous bull. A recently developed method, primer extension preamplification (PEP), was used to amplify the bovine sperm genome prior to amplification of specific loci by the polymerase chain reaction (PCR). At least 28 copies of the DRB3, PRL, or DYA gene were obtained from 50 cycles of PEP. For sperm typing, alleles of each locus were discriminated by restriction endonuclease cleavage of PCR products and polyacrylamide gel electrophoresis of the restriction fragments. The most likely gene order is PRL-DRB3-DYA, with theta = 0.025 (+/- 0.012) and theta = 0.150 (+/- 0.024), respectively. The odds are 128:1 in favor of this order in comparison with the second most likely order DRB3-PRL-DYA. Our results demonstrate the power of sperm typing in concert with PEP for multilocus gene mapping.
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PMID:Order of bovine DRB3, DYA, and PRL determined by sperm typing. 843 35

Activation of immature thymocytes or transformed T lymphocytes via T-cell receptor (TCR)/CD3 signalling can induce programmed cell death (apoptosis). Recent data indicate that anti-CD3/TCR monoclonal antibodies (mAb) also trigger apoptosis in activated (but not resting) mature peripheral blood T lymphocytes. Here we report that triggering of resting CD4-CD8-TCR alpha beta+ and/or TCR gamma delta+ via the alternative CD2-dependent activation pathway is able to induce programmed cell death. A pair of mitogenic anti-CD2 mAb provoked a dramatic rise in [Ca2+]i that was almost entirely sustained by extracellular fluxes, and the inhibition of membrane [Ca2+/Mg2+] ATPase. The resulting endonuclease activation was able to induce DNA fragmentation, as revealed by propidium iodide staining and gel electrophoresis. Induction of apoptosis was prevented by the presence of interleukin-4 (IL-4) as well as by endonuclease inactivation with 100 microM ZnCl2, but enhanced by the contemporary block of protein kinase C. Thus it seems that in resting T lymphocytes the strong calcium signal delivered by the alternative CD2 activation pathway may act as a negative apoptotic signal in both alpha beta and gamma delta T cells with low (non-major histocompatibility complex restricted) antigenic affinity, so limiting the extension of polyclonal T-cell growth.
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PMID:IL-4 is able to reverse the CD2-mediated negative apoptotic signal to CD4-CD8- alpha beta and/or gamma delta T lymphocytes. 855 74

Two DNA-based assays were developed for identification of the H2 alleles present in the 12 standard mouse MHC haplotypes H2b, H2d, H2f, H2j, H2k, H2p, H2q, H2r, H2s, H2u, H2v and H2z. The assays utilized polymerase chain reaction (PCR) amplification of a short stretch of genomic DNA including a highly polymorphic microsatellite from the second intron of the class II Eb gene within the murine major histocompatibility complex. The H2 Eb alleles were discerned by restriction fragment length polymorphism (RFLP) and heteroduplex analyses. For RFLP analysis amplified DNAs were digested with the restriction endonuclease Fnu4HI which delineated seven of the 12 alleles. A distinct pattern was obtained for the haplotypes H2d, H2j, H2k and H2p, whereas a group specific but distinct pattern was obtained for each of the three groups H2b, H2r and H2v, H2f, H2q and H2s, H2u and H2z. Heteroduplex analysis using a pair of haplotypes at a time helped further discriminate H2q from H2f or H2s. More importantly, heteroduplexing was quite informative in delineating the identity or disparity between two given haplotypes in a single step of PCR amplification. Both the RFLP and heteroduplex analyses are extremely sensitive and simple to operate, and since the target is genomic DNA, they can be carried out using any cell or tissue type.
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PMID:Typing of murine major histocompatibility complex with a microsatellite in the class II Eb gene. 869 Sep 43

In order to investigate major histocompatibility complex (MHC) class I chain-related gene A (MICA), tumor necrosis factor (TNFa), -308TNFA, and human leukocyte antigen (HLA-DR/DQ) polymorphisms in mixed connective tissue disease (MCTD), we analyzed 24 patients and 229 healthy controls from Sweden. MICA and TNFa typing was performed by polymerase chain reaction (PCR) and genotyping. HLA-DR and -DQ were genotyped using PCR-sequence specific primers (PCR-SSP) and PCR-sequence-specific oligonucleotide probe (PCR-SSOP), respectively. For analysis of -308TNFA polymorphisms we performed PCR with restriction endonuclease enzymes. We found that the MICA5.1-5.1 genotype was positively associated with MCTD. Shared epitope genes (DRB1*01 and DRB1*04) were also significantly positively associated with MCTD. Polymorphism of -308TNFA was not differently distributed in MCTD patients compared with controls. Furthermore, we demonstrated that frequencies of three estimated haplotypes were increased in MCTD patients compared with controls. Interestingly, the haplotype with MICA allele 4 together with DRB1*04 and TNF1 alleles gives the most specific pattern for MCTD patients compared with controls. Our study demonstrates a clear contribution of HLA loci in susceptibility to MCTD in the Swedish population. Susceptibility to MCTD may be linked to the MICA4/HLA-DRB1*04/TNF1 haplotype and MICA 5.1-5.1 genotype. Mixed connective tissue disease was also associated with shared epitope genes, which in RA has been associated with a more severe disease. Whether these genotypes affect the clinical phenotype of MCTD needs to be determined.
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PMID:MICA4/HLA-DRB1*04/TNF1 haplotype is associated with mixed connective tissue disease in Swedish patients. 1255 32

The major histocompatibility complex (MHC) is a gene complex closely linked to the vertebrate immune system due to its importance in antigen recognition and immune response to pathogens. To improve our understanding of the MHC and disease resistance in dairy cattle, we gathered 5119 test day records of somatic cell count (SCC) and performance traits of 262 Holstein dairy cows to determine whether the DRB region of the MHC contains alleles that are associated with elevated SCC, milk yield, protein and fat percent of milk. To this purpose, genotyping of animals for DRB3 gene was investigated by polymerase chain reaction-based restriction fragment length polymorphism (PCR-RFLP) assay. A two-step PCR was carried out so as to amplify a 284 base-pair fragment of exon 2 of the target gene. Second PCR products were treated with three restriction endonuclease enzymes RsaI, BstYI and HaeIII. Twenty-eight BoLA-DRB3 alleles were identified including one novel allele (*40). The results in general are in good accordance with allele frequencies of Holstein cattle populations reported by previous studies. Analyses of associations were modeled based on repeated measurement anova and generalized logistic linear methods for production traits and SCC data, respectively. The results of this study showed a significant relationship between the elevated SCC reflecting an increased probability of occurrence to subclinical mastitis and DRB3.2 allele *8 (p < 0.03). The results also revealed significant positive relationships of alleles*22 (p < 0.01) and allele*11 (p < 0.05) with milk fat percent as well as of alleles*24 (p < 0.03) and *22 (p < 0.05) with protein percent. The present study failed to find any association between milk yield and tested alleles. Because of the lack of consistency among results of similar studies, we suggest further investigations to determine the precise nature of these associations with the high polymorphic bovine MHC region to be performed based on haplotypes.
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PMID:Analysis of relationship between bovine lymphocyte antigen DRB3.2 alleles, somatic cell count and milk traits in Iranian Holstein population. 1963 Aug 80

Recombination hotspots are the regions within the genome where the rate, and the frequency of recombination are optimum with a size varying from 1 to 2kb. The recombination event is mediated by the double-stranded break formation, guided by the combined enzymatic action of DNA topoisomerase and Spo 11 endonuclease. These regions are distributed non-uniformly throughout the human genome and cause distortions in the genetic map. Numerous lines of evidence suggest that the number of hotspots known in humans has increased manifold in recent years. A few facts about the hotspot evolutions were also put forward, indicating the differences in the hotspot position between chimpanzees and humans. In mice, recombination hot spots were found to be clustered within the major histocompatibility complex (MHC) region. Several models, that help explain meiotic recombination has been proposed. Moreover, scientists also developed some computational tools to locate the hotspot position and estimate their recombination rate in humans is of great interest to population and medical geneticists. Here we reviewed the molecular mechanisms, models and in silico prediction techniques of hot spot residues.
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PMID:Recombination hotspots: Models and tools for detection. 2699 54


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