scholarly journals Defective Brca2 influences topoisomerase I activity in mammalian cells.

2003 ◽  
Vol 50 (1) ◽  
pp. 139-144 ◽  
Author(s):  
Iwonna Rahden-Staroń ◽  
Maria Szumiło ◽  
Emilia Grosicka ◽  
Maria Kraakman van der Zwet ◽  
Małgorzata Z Zdzienicka
Keyword(s):  
Mammalian Cells ◽  
Topoisomerase I ◽  
Chinese Hamster ◽  
Brca2 Gene ◽  
Nuclear Extract ◽  
Chinese Hamster Cell ◽  
V79 Cells ◽  
Cell Mutant ◽  
Relaxation Activity ◽  
Nuclear Extracts

The Chinese hamster cell mutant V-C8 is defective in the Brca2 gene (Kraakman-van der Zwet et al., 2002, Cell Biol.; 22: 669). Here we report that V-C8 cells were 10-fold more sensitive to camptothecin, an inhibitor of topoisomerase I, than the parental V79 cells. The level of the relaxation activity of topoisomerase I in nuclear extracts was also lower (4-fold) in V-C8 than V79 cells, in spite of the fact that the level of the topoisomerase I protein was the same in these cells. The survival of V-C8 cells in the presence of camptothecin, the sensitivity of V-C8 topoisomerase I to camptothecin, and the level of the relaxation activity in V-C8 nuclear extract were almost completely restored by transfection of V-C8 cells with the murine Brca2 gene or by the transfer of human chromosome 13 providing the BRCA2 gene. These results indicate that the observed changes in the topoisomerase I activity in V-C8 are due to the defective function of the Brca2 gene.

Chinese hamster cell mutant, V-C8, a model for analysis of Brca2 function

2006 ◽  
Vol 600 (1-2) ◽  
pp. 79-88 ◽  
Author(s):  
Wouter W. Wiegant ◽  
René M. Overmeer ◽  
Barbara C. Godthelp ◽  
Paul P.W. van Buul ◽  
Małgorzata Z. Zdzienicka
Keyword(s):  
Chinese Hamster ◽  
Chinese Hamster Cell ◽  
Cell Mutant

scholarly journals DNA strand specificity for UV-induced mutations in mammalian cells.

1989 ◽  
Vol 9 (3) ◽  
pp. 1277-1283 ◽  
Author(s):  
H Vrieling ◽  
M L Van Rooijen ◽  
N A Groen ◽  
M Z Zdzienicka ◽  
J W Simons ◽  
...  
Keyword(s):  
Dna Replication ◽  
Base Pair ◽  
Mammalian Cells ◽  
Chinese Hamster ◽  
Parental Line ◽  
Induced Mutations ◽  
Hprt Gene ◽  
V79 Cells ◽  
H1 Cells ◽  
Double Base

The influence of DNA repair on the molecular nature of mutations induced by UV light (254 nm) was investigated in UV-induced hprt mutants from UV-sensitive Chinese hamster cells (V-H1) and the parental line (V79). The nature of point mutations in hprt exon sequences was determined for 19 hprt mutants of V79 and for 17 hprt mutants of V-H1 cells by sequence analysis of in vitro-amplified hprt cDNA. The mutation spectrum in V79 cells consisted of single- and tandem double-base pair changes, while in V-H1 cells three frameshift mutations were also detected. All base pair changes in V-H1 mutants were due to GC----AT transitions. In contrast, in V79 all possible classes of base pair changes except the GC----CG transversion were present. In this group, 70% of the mutations were transversions. Since all mutations except one did occur at dipyrimidine sites, the assumption was made that they were caused by UV-induced photoproducts at these sites. In V79 cells, 11 out of 17 base pair changes were caused by photoproducts in the nontranscribed strand of the hprt gene. However, in V-H1 cells, which are completely deficient in the removal of pyrimidine dimers from the hprt gene and which show a UV-induced mutation frequency enhanced seven times, 10 out of 11 base pair changes were caused by photoproducts in the transcribed strand of the hprt gene. We hypothesize that this extreme strand specificity in V-H1 cells is due to differences in fidelity of DNA replication of the leading and the lagging strand. Furthermore, we propose that in normal V79 cells two processes determine the strand specificity of UV-induced mutations in the hprt gene, namely preferential repair of the transcribed strand of the hprt gene and a higher fidelity of DNA replication of the nontranscribed strand compared with the transcribed strand.

A novel type of X-ray-sensitive Chinese hamster cell mutant with radioresistant DNA synthesis and hampered DNA double-strand break repair

1995 ◽  
Vol 337 (2) ◽  
pp. 119-129 ◽  
Author(s):  
Gerald W.C.T Verhaegh ◽  
Wim Jongmans ◽  
Bruno Morolli ◽  
Nicolaas G.J Jaspers ◽  
Govert P van der Schans ◽  
...  
Keyword(s):  
Dna Synthesis ◽  
Chinese Hamster ◽  
Strand Break ◽  
Chinese Hamster Cell ◽  
Double Strand Break ◽  
Double Strand Break Repair ◽  
Cell Mutant ◽  
X Ray ◽  
Dna Double Strand Break ◽  
Break Repair

Characterization of DNA end joining in a mammalian cell nuclear extract: junction formation is accompanied by nucleotide loss, which is limited and uniform but not site specific

1994 ◽  
Vol 14 (1) ◽  
pp. 170-180
Author(s):  
A L Nicolás ◽  
C S Young
Keyword(s):  
Mammalian Cell ◽  
Mammalian Cells ◽  
Nuclear Extract ◽  
Major Effect ◽  
Cell Nuclei ◽  
Site Specific ◽  
Preferential Formation ◽  
Nuclear Extracts ◽  
Dna Substrates ◽  
Molecular And Biochemical Mechanisms

Mammalian cells have a marked capacity to repair double-strand breaks in DNA, but the molecular and biochemical mechanisms underlying this process are largely unknown. A previous report has described an activity from mammalian cell nuclei that is capable of multimerizing blunt-ended DNA substrates (R. Fishel, M.K. Derbyshire, S.P. Moore, and C.S.H. Young, Biochimie 73:257-267, 1991). In this report, we show that nuclear extracts from HeLa cells contain activities which preferentially join linear plasmid substrates in either a head-to-head or tail-to-tail configuration, that the joining reaction is covalent, and that the joining is accompanied by loss of sequence at the junction. Sequencing revealed that there was a loss of a uniform number of nucleotides from junctions formed from any one type of substrate. The loss was not determined by any simple site-specific mechanism, but the number of nucleotides lost was affected by the precise terminal sequence. There was no major effect on the efficiency or outcome of the joining reaction with substrates containing blunt ends or 3' or 5' protruding ends. Using a pair of plasmid molecules with distinguishable restriction enzyme sites, we also observed that blunt-ended DNA substrates could join with those containing protruding 3' ends. As with the junctions formed between molecules with identical ends, there was uniform loss of nucleotides. Taken together, the data are consistent with two models for the joining reaction in which molecules are aligned either throughout most of their length or by using small sequence homologies located toward their ends. Although either model can explain the preferential formation of head-to-head and tail-to-tail products, the latter predicts the precise lossof nucleotides observed. These activities are found in all cell lines examined so far and most likely represent an important repair activity of the mammalian cell.

scholarly journals Characterization of DNA end joining in a mammalian cell nuclear extract: junction formation is accompanied by nucleotide loss, which is limited and uniform but not site specific.

1994 ◽  
Vol 14 (1) ◽  
pp. 170-180 ◽  
Author(s):  
A L Nicolás ◽  
C S Young
Keyword(s):  
Mammalian Cell ◽  
Mammalian Cells ◽  
Nuclear Extract ◽  
Major Effect ◽  
Cell Nuclei ◽  
Site Specific ◽  
Preferential Formation ◽  
Nuclear Extracts ◽  
Dna Substrates ◽  
Molecular And Biochemical Mechanisms

Mammalian cells have a marked capacity to repair double-strand breaks in DNA, but the molecular and biochemical mechanisms underlying this process are largely unknown. A previous report has described an activity from mammalian cell nuclei that is capable of multimerizing blunt-ended DNA substrates (R. Fishel, M.K. Derbyshire, S.P. Moore, and C.S.H. Young, Biochimie 73:257-267, 1991). In this report, we show that nuclear extracts from HeLa cells contain activities which preferentially join linear plasmid substrates in either a head-to-head or tail-to-tail configuration, that the joining reaction is covalent, and that the joining is accompanied by loss of sequence at the junction. Sequencing revealed that there was a loss of a uniform number of nucleotides from junctions formed from any one type of substrate. The loss was not determined by any simple site-specific mechanism, but the number of nucleotides lost was affected by the precise terminal sequence. There was no major effect on the efficiency or outcome of the joining reaction with substrates containing blunt ends or 3' or 5' protruding ends. Using a pair of plasmid molecules with distinguishable restriction enzyme sites, we also observed that blunt-ended DNA substrates could join with those containing protruding 3' ends. As with the junctions formed between molecules with identical ends, there was uniform loss of nucleotides. Taken together, the data are consistent with two models for the joining reaction in which molecules are aligned either throughout most of their length or by using small sequence homologies located toward their ends. Although either model can explain the preferential formation of head-to-head and tail-to-tail products, the latter predicts the precise lossof nucleotides observed. These activities are found in all cell lines examined so far and most likely represent an important repair activity of the mammalian cell.

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