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)

Detailed restriction endonuclease maps were developed for Harvey murine sarcoma virus (Ha-MuSV) DNA (clone H-1), molecularly closed at its unique EcoRI site in pBR322, for three nonoverlapping subgenomic HindIII clones which together span the entire H-1 clone and for a molecularly cloned DNA copy of a portion of rat 30S RNA (which represents the majority of the rat genetic sequences in Ha-MuSV). Molecular hybridization of the 30S clone to small restriction fragments of clone H-1 revealed a 0.9-to-1.0-kilobase pair region in the 5' half of the Ha-MuSV genome not homologous to the 30S clone, although the 30S clone did contain related sequences in Ha-MuSV on both sides of this nonhomologous region. By using cloned sequences from a segment of the Ha-MuSV nonhomology region as a probe for hybridization to Southern blots of DNA from rat, mouse, bat, and chicken cells, one to three bands were detected in DNA of each species. By contrast, the 30S clone DNA was highly related to many sequences in rat DNA, partially related to fewer mouse DNA sequences, and homologous only to one to three bands in bat and chicken DNA. Earlier work had shown that the 5' half of the Ha-MuSV genome coded for transformation and for the viral p21 protein (Chang et al., J. Virol. 35: 76--92, 1980; Wei et al., Proc. Natl. Acad. Sci. U.S.A., in press). We used two subgenomic HindIII clones whose shared HindIII site mapped within the 5' region of clone H-1 nonhomologous to the 30S clone to test whether the nonhomologous segment might encode the transforming and p21 functions. Although neither of the subgenomic HindIII fragments by themselves induced transformation, ligation of these two nontransforming DNAs to each other did restore p21-mediated transformation. A conclusion consistent with these results is that a region in the 5' half of the Ha-MuSV genome evolutionarily distinct from and not present in rat 30S RNA is essential for transformation and for p21 encoding.
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PMID:Dual evolutionary origin for the rat genetic sequences of Harvey murine sarcoma virus. 625 66

Harvey murine sarcoma virus (Ha-MuSV) is a mouse-rat recombinant retrovirus that encodes a protein designated p21, required for virally induced transformation. Using a radiolabeled DNA fragment from the p21 coding region, we have detected homologous DNA sequences in the normal DNA of rats and of several other vertebrate species. Moreover, many tested cells from these species contain low levels of a p21 protein that is highly related to viral 21. Now we report two independent fragments from normal rat DNA containing sequences (sarc) homologous to the Ha-MuSV transforming region that were cloned in the bacteriophage vector Charon 4A. Sarc sequences in the one fragment are completely colinear with the viral sequences and share apparently all restriction endonuclease sites. Sarc sequences in the second fragment have several sets of intervening sequences and lack some restriction endonuclease sites found in the viral transforming region. Despite the presence of these intervening sequences in the second sarc fragment, we have been able to ligate this sarc fragment to the long terminal repeat sequence of HaMuSV and to induce cellular transformation and high levels of p21 expression upon transfection of this DNA to NIH 3T3 mouse cells. These results suggest that elevated levels of p21, normally expressed at low levels in a variety of cells, can induce cellular transformation.
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PMID:Analysis of two divergent rat genomic clones homologous to the transforming gene of Harvey murine sarcoma virus. 626 83

Cancer development requires the accumulation of numerous genetic changes, which are believed to initiate through the presence of unrepaired lesions in the genome. In the absence of proficient repair, genotoxic agents can lead to crucial mutations of vital cellular genes via replication of damaged DNA. Many cell cycle regulatory proteins are known to modulate the repair capacity and consequently the fate of cells. We and others have recently shown that p53 tumor suppressor gene product is required for efficient global genomic repair (GGR) but not the transcription coupled repair (TCR) of the nucleotide excision repair (NER) sub-pathways. In order to discern the nature of the p53 modulation to be direct or indirect through a downstream mediator, we have investigated the processing of UV radiation induced lesions in human colon carcinoma, HCT116 cells expressing wild-type p53 but having different p21(waf1cip1) (hereafter p21) genotypes (p21+/+, p21+/-, p21-/-). Following 20 J/m(2) UV, all the three cell lines showed rapid increase in p53 protein but the accompanying increase in the expression of its downstream target protein p21 could only be seen in p21+/+ and p21+/- cells and not in p21-/- cells. Nevertheless, an absence of detectable p21 protein in deficient cells had no demonstrable effect on DNA repair response to UV irradiation, as measured by an immunoassay to detect removal of UV photoproducts from genomic DNA (GGR) and by individual strand specific removal of endonuclease-sensitive CPD from a target gene fragment (TCR). Introduction of cytomegalovirus (CMV)-driven luciferase reporter plasmid, UV damaged in vitro, into the un-irradiated cells of varying p21 background, revealed a relatively small but statistically significant decrease in the reporter expression in the host p21-/- as compared with p21+/+ and p21+/- HCT116 cells. Super-expression of p21 protein upon reintroduction of p21 expression construct, showed an enhanced recovery of UV damaged reporter activity that was not greatly different from a similar enhancement observed with undamaged plasmid reporter DNA. Taken together, the results indicate that (i) the p21 protein does not have a significant role in the repair of genomic DNA at chromosomal level; (ii) the well-established p53 dependent modulation of NER is distinct and independent of its cell cycle checkpoint function; and (iii) the reproducible enhancing effect of p21 expression observed through host cell reactivation (HCR) of extrachromosomal DNA is mainly attributable to an effect exerted on transcription rather than repair.
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PMID:Human cells deficient in p53 regulated p21(waf1/cip1) expression exhibit normal nucleotide excision repair of UV-induced DNA damage. 1189 54