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 integrated proviral DNA of the polycythemia-inducing isolate of Friend spleen focus-forming virus (SFFVp) has been identified in rat cell clones nonproductively infected with this replication-defective erythroleukemia virus and cloned in phage lambda vectors. These lambda SFFVp recombinants, lambda SFFVp502 and lambda SFFVp542, contain endonuclease EcoRI inserts of size 7.4 and 8.2 kilobases, respectively, and include full copies of the SFFVp genome, along with host flanking sequences. Infectivity of the cloned SFFVp genomes was tested by a two-step DNA transfer procedure involving transfection of the cloned DNA into 3T3 mouse fibroblasts or cotransfer of the cloned DNA into thymidine kinase-deficient 3T3 cells together with the cloned thymidine kinase gene of herpes simplex virus, followed by rescue of the transferred DNA by superinfection with a helper virus. Inoculation of the rescued virus into adult mice resulted in the appearance of spleen foci, rapid splenomegaly, and polycythemia. Early after infection, spleen cell populations contained large numbers of cells capable of forming small erythroid colonies in vitro (CFU-E) in the absence of erythropoietin. Late after infection, these mice contained cells capable of forming macroscopic colonies (CFU-FV) in vitro. These data indicate that molecular clones of SFFVp, in conjunction with a helper virus, induce the appearance of hemopoietic colony-forming cells characteristic of both the early and late stages of Friend leukemia.
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PMID:Clonal analysis of early and late stages of erythroleukemia induced by molecular clones of integrated spleen focus-forming virus. 627 94

Globin structural genes from a murine erythroleukemia cell line were analyzed by Southern blot hybridization of genomic DNA and after isolation of cloned globin genes from a genomic library. The globin genes isolated from the erythroid cell line did not differ, when analyzed by extensive restriction endonuclease digestion, from globin genes isolated from nonerythroid cells. No gross structural differences were seen between murine erythroleukemia globin genes, either before or after hexamethylene bisacetamide (HMBA)-mediated erythroid differentiation, and globin genes from normal mouse liver DNA. Whereas the murine erythroleukemia genome hybridizes extensively to cloned Friend leukemia virus probes, there was no evidence of viral integration into sequences adjacent to the globin genes.
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PMID:Analysis of globin genes from murine erythroleukemia cells. 630 19

A pseudogene related to the functional gene (FECH) for the heme biosynthetic enzyme ferrochelatase (ferroheme-protolyase; EC 4.99.1.1.) was isolated from a human genomic library using a ferrochelatase cDNA hybridization probe. The pseudogene shows > 80% overall nucleotide sequence identity to the functional gene (including the 3' untranslated region and polyadenylation signals) but contains no intronic sequences in the region corresponding to the open reading frame of expressed ferrochelatase. Furthermore, the pseudogene sequence contains small deletions and insertions creating frameshifts and numerous termination codons, indicating that it does not encode a functional polypeptide. Northern blot analysis using pseudogene-specific probes failed to demonstrate transcripts in samples of human erythroid cell RNA in which ferrochelatase mRNA was readily detected. Southern blot experiments using restriction endonuclease-digested human genomic DNA probed either with ferrochelatase-specific cDNA fragments or pseudogene-specific genomic sequences confirmed the presence of distinct loci for the expressed and nonfunctional genes, respectively. Localization of the human ferrochelatase pseudogene to 3p22-p23 was determined by fluorescent metaphase chromosomal hybridization in situ using three genomic clones in lambda EMBL3 spanning a contiguous region of approximately 30 kb. This newly identified locus, distinct from the expressed FECH gene, on 18q22, is characteristic of a processed human pseudogene. The existence of the ferrochelatase pseudogene has practical implications for the molecular analysis of mutations responsible for erythropoietic protoporphyria in man.
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PMID:Molecular analysis of functional and nonfunctional genes for human ferrochelatase: isolation and characterization of a FECH pseudogene and its sublocalization on chromosome 3. 803 22

We examined the endonuclease activity capable of inducing internucleosomal DNA fragmentation in hematopoietic cells. Mg(2+)-dependent nuclease activity was high in hematopoietic progenitor cells and the activity decreased with myeloid or erythroid differentiation. This was the case in MDS as well as in normal hematopoiesis. In contrast, Ca2+/Mg(2+)-dependent nuclease activity varied widely in the samples from MDS and the possibility was indicated that the activity of Glycophorin A+ cells was related to the degree of anemia. We also investigated DNA strand breaks in bone marrow samples from 16 patients with MDS and 10 with other diseases by an in situ end labeling (ISEL) technique. The reactivity in ISEL tended to increase parallel to disease progression of MDS. The high ISEL-positivity was also observed in some samples from patients with MPD and other diseases. Though ISEL is a useful technique for quantification of apoptosis, our results suggested that MDS cells with ISEL positive staining are not necessarily in the process of apoptosis.
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PMID:[Apoptosis in MDS]. 877 68

Endonucleases capable of producing internucleosomal DNA cleavage are one of the key enzymes in apoptosis. We examined endonuclease activities contained in nuclei of CD34+ and erythroid cells in the bone marrow (BM) from 12 patients with the myelodysplastic syndromes. The levels of Mg(2+)-dependent and acidic endonucleases showed little changes as compared with those from normal BM. By contrast, the level of Ca2+/Mg(2+)-dependent endonuclease was appreciably higher in MDS erythroid cells than normal counterparts, although the activity varied markedly in CD34+ and erythroid cells. Our results suggested that Ca2+/Mg(2+)-dependent endonuclease is related to ineffective erythropoiesis in MDS.
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PMID:Ca2+/Mg(2+)-dependent endonuclease in marrow CD34 positive and erythroid cells in myelodysplasia. 937 80

The stem cell leukaemia (SCL) gene is a member of the basic helix-loop-helix family of transcription factors and is essential for the development of all haematopoietic lineages. SCL is expressed in pluripotent haematopoietic stem cells and also following commitment to the erythroid, mast and megakaryocytic lineages. The mechanisms responsible for this pattern of expression are poorly understood, but are likely to illuminate the molecular basis for stem cell development and lineage commitment. Here we present the first description of the regulation of the SCL gene in mast cells. In this study we systematically analysed the chromatin structure of a 45 kb region of the murine SCL locus in mast cells. The pattern of DNase 1 and restriction endonuclease hypersensitive sites in mast cells was distinct from, but overlapped with, the pattern previously described in erythroid and primitive myeloid cells. Each potential regulatory element was tested using transient reporter assays to assess their functional significance in mast cells. These studies identified two potent enhancers, one of which was downstream of the SCL gene. Further characterisation of this 3' enhancer demonstrated that it required the presence of two distinct DNase 1 hypersensitive sites for full activity, and that it was capable of stimulating transcription from both promoter 1a and 1b. Since the 3' enhancer is active in both erythroid and mast cells, it will now be important to see whether it is independently activated in these lineages, or whether it is also active in haematopoietic stem cells.
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PMID:Chromatin structure and transcriptional regulation of the stem cell leukaemia (SCL) gene in mast cells. 1037 80

Proteosomes from human proerythroleukaemic cell line K562 are found to degrade high molecular weight cytoplasmic RNAs, particularly ribosomal and specific messenger RNA. This activity was observed to be endoribonucleotylic. The induction of differentiation by erythroid pathway in K562 cells invokes augmentation of endonuclease activity in proteasomes. The number of characteristics of this enzymatic activity was investigated. Specificity of endonuclease of these RNPs is shown to be Ca- and Mg-dependent. Dephosphorylation of protein subunits suppresses RNase activity of proteasomes. Endonuclease of proteasomes is thermolabile. The examined activity depends on the secondary structure of substrate RNA. Protein subunits are responsible for ribonuclease activity of proteasomes rather than for low molecular weight RNAs associated with the complex.
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PMID:[Characteristics of endoribonuclease activity of proteasomes from K562 cells. I. Dependence of RNAase activity of proteasome and alph-RNP on conditions of endonucleolysis reaction]. 1205 69

Previous work showed that human beta-globin mRNAs harboring a premature termination codon are degraded in the erythroid tissues of mice to products that lack sequences from the mRNA 5' end but contain a 5' cap-like structure. Whether these decay products are the consequence of endonucleolytic or 5'-to-3' exonucleolytic activity is unclear. We report that this beta-globin mRNA decay pathway is recapitulated in cultured mouse erythroleukemia (MEL) cells and targets nonsense-free mRNA to a lesser extent than nonsense-containing mRNA. S1 nuclease mapping and primer extension demonstrated that 70-80% of decay product 5' ends contain a UG dinucleotide. Detection of upstream counterparts of these decay products indicates that they are generated by endonucleolytic activity. Both crude and partially purified polysome extracts prepared from MEL cells contain an endonucleolytic activity that generates decay products comparable to those observed in vivo. These data suggest that an endonuclease with preference for UG dinucleotides is involved in the degradation of nonsense-containing and, to a lesser extent, nonsense-free human beta-globin mRNAs in mouse erythroid cells.
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PMID:Beta -Globin mRNA decay in erythroid cells: UG site-preferred endonucleolytic cleavage that is augmented by a premature termination codon. 1224 35

beta-globin mRNA bearing a nonsense codon is degraded in the cytoplasm of erythroid cells by endonuclease cleavage, preferentially at UG dinucleotides. An endonuclease activity in polysomes of MEL cells cleaved beta-globin and albumin mRNA in vitro at many of the same sites as PMR1, an mRNA endonuclease purified from Xenopus liver. Stable transfection of MEL cells expressing normal human beta-globin mRNA with a plasmid vector expressing the catalytically active form of PMR1 reduced the half-life of beta-globin mRNA from 12 to 1-2 h without altering GAPDH mRNA decay. The reduced stability of beta-globin mRNA in these cells was accompanied by an increase in the production of mRNA decay products corresponding to those seen in the degradation of nonsense-containing beta-globin mRNA. Therefore, beta-globin mRNA is cleaved in vivo by an endonuclease with properties similar to PMR1. Inhibiting translation with cycloheximide stabilized nonsense-containing beta-globin mRNA, resulting in a fivefold increase in its steady-state level. Taken together, our results indicate that the surveillance of nonsense-containing beta-globin mRNA in erythroid cells is a cytoplasmic process that functions on translating mRNA, and endonucleolytic cleavage constitutes one step in the process of beta-globin mRNA decay.
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PMID:An endonuclease activity similar to Xenopus PMR1 catalyzes the degradation of normal and nonsense-containing human beta-globin mRNA in erythroid cells. 1292 63

There is still no clarity on whether the endonuclease incisions in apoptotic cells are induced randomly in the genome or induced in some preferable sites. In order to evaluate the intensity of DNA fragmentation in the chicken alpha-globin domain, AEV-virus transformed chicken erythroblasts (HD3) were incubated in a serum free medium, and their DNA was Southern blotted and hybridised with probes representing different fragments of the domain. Probes corresponding to the upstream areas of the domain mostly hybridised with high molecular weight DNA. Unlike these, the probe corresponding to the 2 Kb BamHI-BamHI fragment, containing the alphaA globin gene (B18), revealed a 5 Kb band on the hybridisation autoradiographs. The probe to the neighbouring upstream fragment did not reveal this band, but it was clearly seen on hybridisations with a downstream 1 Kb BamHI-BamHI fragment. The intensity of the band increased with overall apoptotic DNA degradation, hence its appearance should be coupled to apoptosis. Hybridisation of BamHI-digested DNA with B18 probe revealed a shortening of the 2 Kb band in preparations of DNA from apoptotic cells. The presumable positions of the cuts correspond to the formerly described DNase hypersensitive sites in the domain. Slot-blot and Northern hybridisation of RNA extracted from apoptotic HD3 cells revealed that the excision of the area of the B18 gene is coupled to a decrease in the intensity of alphaA globin gene transcription. Transcription of the non-erythroid NIK gene, transcribed in the upstream part of the domain, did not depend on the level of apoptotic DNA fragmentation.
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PMID:Site-specific excision or protection of an alpha A globin gene genomic site in apoptotic transformed chicken erythroblasts. 1533 20


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