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)

Attempts to activate type C endogenous viruses in 129 mouse fibroblasts and in teratocarcinoma-derived cell lines have never been successful, although the genome of these cells contains xenotropic virus-related sequences. We have investigated the arrangement of these sequences and their methylation state by DNA restriction endonuclease digestion, electrophoresis of digests in agarose gels, Southern blotting and hybridization with specific probes. Our results show that the majority of the sequences are organized into two complete provirus families integrated at multiple sites in the cell genome and that they are hypermethylated in embryonal carcinoma cells as compared with differentiated cells. Having previously found a higher expression of viral RNA in 129 derived embryonal carcinoma cells, our data indicate an apparent direct correlation between methylation and type C virogenes expression.
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PMID:Organization and state of methylation of endogenous type C retroviral sequences in 129 mouse differentiated and undifferentiated teratocarcinoma cell lines. 298 55

A small circular DNA was found extrachromosomally in a clone of F9 embryonal carcinoma (EC) cells at high copy numbers per cell. The DNA was cloned in plasmid pUC19. Restriction endonuclease analyses of the DNA indicated that the DNA (fPyF9) was a mutant of polyomavirus (Py) DNA and had a mutation in a noncoding regulatory region. There have been many reports on the isolation of Py mutants capable of replication in undifferentiated cells. However, fPyF9 was different from other Py mutants in the following aspects: it was harbored stably as a free copy at 1 X 10(4) to 5 X 10(4) copies per cell in EC cells; it replicated in undifferentiated cells better than in differentiated cells; it was extremely rearranged in the sequences of the enhancer B domain; and it carried in the enhancer B domain three copies of an exogenous sequence which does not exist in Py strain A2. From these observations, we propose a new class of Py EC mutant which has an autonomous state similar to that of plasmid and small circular DNA in host cells.
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PMID:New class of polyomavirus mutant that can persist as free copies in F9 embryonal carcinoma cells. 302 19

Embryonal carcinoma (EC) mouse cells have been shown to be resistant to infection by retroviruses and small oncogenic DNA viruses, including simian virus 40 and polyoma. When allowed to differentiate, in vitro or in vivo, EC cells become as susceptible to these viruses as differentiated mouse cell lines are. In order to study the relationships between differentiation of EC cells and viral expression, we have isolated and characterized several polyoma mutants that can express early and late functions in undifferentiated EC cells. These mutants, which arose spontaneously during high-multiplicity infection of PCD3 cells (a differentiated fibroblast-like cell line derived from PCC3 EC cells), were selected on PCC4 cells (undifferentiated EC cells) and twice plaque purified. Restriction enzyme analysis of the DNA from several mutants has shown that they all exhibit an additional sequence located in the Pvu II endonuclease fragment 4, close to the junction between Hpa II endonuclease fragments 3 and 5. The size of the insertion varies from 10 to 50 base pairs. The biological properties, including oncogenicity, transforming ability, host range, and burst size of the mutants so far analyzed are similar to those of wild-type virus.
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PMID:Isolation and characterization of polyoma virus mutants able to develop in embryonal carcinoma cells. 624 78

Histone acetylation is thought to have a role in transcription. To gain insight into the role of histone acetylation in retinoid-dependent transcription, we studied the effects of trichostatin A (TSA), a specific inhibitor of histone deacetylase, on P19 embryonal carcinoma cells. We show that coaddition of TSA and retinoic acid (RA) markedly enhances neuronal differentiation in these cells, although TSA alone does not induce differentiation but causes extensive apoptosis. Consistent with the cooperative effect of TSA and RA, coaddition of the two agents synergistically enhanced transcription from stably integrated RA-responsive promoters. The transcriptional synergy by TSA and RA required the RA-responsive element and a functional retinoid X receptor (RXR)/retinoic acid receptor (RAR) heterodimer, both obligatory for RA-dependent transcription. Furthermore, TSA led to promoter activation by an RXR-selective ligand that was otherwise inactive in transcription. In addition, TSA enhanced transcription from a minimum basal promoter, independently of the RA-responsive element. Finally, we show that TSA alone or in combination with RA increases in vivo endonuclease sensitivity within the RA-responsive promoter, suggesting that TSA treatment might alter a local chromatin environment to enhance RXR/RAR heterodimer action. Thus, these results indicate that histone acetylation influences activity of the heterodimer, which is in line with the observed interaction between the RXR/RAR heterodimer and a histone acetylase presented elsewhere.
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PMID:A histone deacetylase inhibitor potentiates retinoid receptor action in embryonal carcinoma cells. 932 3

The vast majority of fragile-X full mutations are heavily methylated throughout the expanded CGG repeat and the surrounding CpG island. Hypermethylation initiates and/or stabilizes transcriptional inactivation of the FMR1 gene, which causes the fragile X-syndrome phenotype characterized, primarily, by mental retardation. The relation between repeat expansion and hypermethylation is not well understood nor is it absolute, as demonstrated by the identification of nonretarded males who carry hypomethylated full mutations. To better characterize the methylation pattern in a patient who carries a hypomethylated full mutation of approximately 60-700 repeats, we have evaluated methylation with the McrBC endonuclease, which allows analysis of numerous sites in the FMR1 CpG island, including those located within the CGG repeat. We report that the expanded-repeat region is completely free of methylation in this full-mutation male. Significantly, this lack of methylation appears to be specific to the expanded FMR1 CGG-repeat region, because various linked and unlinked repetitive-element loci are methylated normally. This finding demonstrates that the lack of methylation in the expanded CGG-repeat region is not associated with a global defect in methylation of highly repeated DNA sequences. We also report that de novo methylation of the expanded CGG-repeat region does not occur when it is moved via microcell-mediated chromosome transfer into a de novo methylation-competent mouse embryonal carcinoma cell line.
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PMID:Hypomethylation of an expanded FMR1 allele is not associated with a global DNA methylation defect. 1052 3

Adeno-associated virus (AAV) type 2 Rep78 is a multifunctional protein required for AAV DNA replication, integration, and gene regulation. The biochemical activities of Rep78 have been described, but the effects of Rep proteins on the cell have not been characterized. We have analyzed Rep-mediated cytotoxicity. We demonstrated that Rep78 expression is sufficient to induce cell death and disruption of the cell cycle. Cell death was found to be mediated by apoptosis. Rep78 expression resulted in the activation of caspase-3, a terminal caspase directly involved in the execution of cell death. A peptidic inhibitor of caspase-3, Z-Asp-Glu-Val-Asp-fluoromethylketone (Z-DEVD-FMK), abrogated Rep78-induced apoptosis, indicating that Rep78-mediated apoptosis is caspase-3 dependent. Rep78 induced apoptosis in wild-type p53-containing human embryonal carcinoma NT-2 cells and in p53-null promyelocytic human HL-60 cells, indicating that at least one pathway of Rep78-induced apoptosis is p53 independent. Apoptosis was shown to occur during the G(1) and early S phases of the cell cycle. By analyzing the effects of Rep78 mutations on cell viability, the cause of cell death was attributed in part to two biochemical activities of Rep78, DNA binding and ATPase/helicase activity. The endonuclease activity of Rep78 did not contribute to apoptosis induction.
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PMID:Adeno-associated virus type 2 Rep78 induces apoptosis through caspase activation independently of p53. 1100 Feb 13

Testicular germ cell tumors (TGCTs) are typically exquisitely sensitive to DNA interstrand cross-link (ICLs) agents. ICLs covalently link both strands of the DNA duplex, impeding fundamental cellular processes like DNA replication to cause cell death. A leading drug used for the treatment of TGCTs is cisplatin, which introduces ICLs and leads to formation of double strand breaks (DSBs), a DNA lesion that can be repaired in the S/G2 phases of the cell cycle by homologous recombination (HR, also termed homology-direct repair). Although most TGCTs respond to cisplatin-induced ICLs, a fraction is resistant to treatment. One proposed mechanism of TGCT resistance to cisplatin is an enhanced ability to repair DSBs by HR. Other than HR, repair of the ICL-lesions requires additional DNA repair mechanisms, whose action might also be implemented in therapy-resistant cells. This chapter describes GFP assays to measure (a) HR proficiency following formation of a DSB by the endonuclease I-SceI, and (b) HR repair induced by site-specific ICL formation involving psoralen. These experimental approaches can be used to determine the proficiency of TGCT cell lines in DSB repair by HR in comparison to HR repair of ICLs, providing tools to better characterize their recombination profile. Protocols of these assays have been adapted for use in Embryonal Carcinoma (EC) TGCT cell lines. Assays only require transient introduction of plasmids within cells, affording the advantage of testing multiple cell lines in a relatively short time.
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PMID:Assessing Homologous Recombination and Interstrand Cross-Link Repair in Embryonal Carcinoma Testicular Germ Cell Tumor Cell Lines. 3285 61