scholarly journals Structure of the dihydrofolate reductase gene in Chinese hamster ovary cells

1983 ◽  
Vol 11 (7) ◽  
pp. 1997-2012 ◽  
Author(s):  
Adelaide M. Carothers ◽  
Gail Urlaub ◽  
Nathan Ellis ◽  
Lawrence A. Chasin
Keyword(s):  
Dihydrofolate Reductase ◽  
Chinese Hamster Ovary ◽  
Chinese Hamster Ovary Cells ◽  
Chinese Hamster ◽  
Ovary Cells ◽  
Reductase Gene

scholarly journals Overproduction of dihydrofolate reductase and gene amplification in methotrexate-resistant Chinese hamster ovary cells.

1982 ◽  
Vol 2 (3) ◽  
pp. 275-285 ◽  
Author(s):  
W F Flintoff ◽  
M K Weber ◽  
C R Nagainis ◽  
A K Essani ◽  
D Robertson ◽  
...  
Keyword(s):  
Dihydrofolate Reductase ◽  
Chinese Hamster Ovary ◽  
Selection Process ◽  
Chinese Hamster Ovary Cells ◽  
Cdna Probe ◽  
Chinese Hamster ◽  
Wild Type Enzyme ◽  
Ovary Cells ◽  
Reductase Gene ◽  
Elevated Rate

Stable isolates of Chinese hamster ovary cells that are highly resistant to methotrexate have been selected in a multistep selection process. Quantitative immunoprecipitations have indicated that these isolates synthesize dihydrofolate reductase at an elevated rate over its synthesis in sensitive cells. Restriction enzyme and Southern blot analyses with a murine reductase cDNA probe indicate that the highly resistant isolates contain amplifications of the dihydrofolate reductase gene number. Depending upon the parenteral line used to select these resistant cells, they overproduce either a wild-type enzyme or a structurally altered enzyme. Karyotype analysis shows that some of these isolates contain chromosomes with homogeneously staining regions whereas others do not contain such chromosomes.

Effects of palindrome structure on dihydrofolate reductase gene amplification in Chinese hamster ovary cells

2009 ◽  
Vol 108 ◽  
pp. S9
Author(s):  
Joon Young Park ◽  
Yasuhiro Takagi ◽  
Miyuki Yamatani ◽  
Kohsuke Honda ◽  
Takeshi Omasa ◽  
...  
Keyword(s):  
Gene Amplification ◽  
Dihydrofolate Reductase ◽  
Chinese Hamster Ovary ◽  
Chinese Hamster Ovary Cells ◽  
Chinese Hamster ◽  
Ovary Cells ◽  
Reductase Gene

scholarly journals Functional nucleotide excision repair is required for the preferential removal of N-ethylpurines from the transcribed strand of the dihydrofolate reductase gene of Chinese hamster ovary cells.

1997 ◽  
Vol 17 (2) ◽  
pp. 564-570 ◽  
Author(s):  
A Sitaram ◽  
G Plitas ◽  
W Wang ◽  
D A Scicchitano
Keyword(s):  
Nucleotide Excision Repair ◽  
Dihydrofolate Reductase ◽  
Chinese Hamster Ovary ◽  
Excision Repair ◽  
Chinese Hamster Ovary Cells ◽  
Alkylating Agents ◽  
Chinese Hamster ◽  
Ovary Cells ◽  
Reductase Gene ◽  
Nucleotide Excision

Transcription-coupled repair of DNA adducts is an essential factor that must be considered when one is elucidating biological endpoints resulting from exposure to genotoxic agents. Alkylating agents comprise one group of chemical compounds which modify DNA by reacting with oxygen and nitrogen atoms in the bases of the double helix. To discern the role of transcription-coupled DNA repair of N-ethylpurines present in discrete genetic domains, Chinese hamster ovary cells were exposed to N-ethyl-N-nitrosourea, and the clearance of the damage from the dihydrofolate reductase gene was investigated. The results indicate that N-ethylpurines were removed from the dihydrofolate reductase gene of nucleotide excision repair-proficient Chinese hamster ovary cells; furthermore, when repair rates in the individual strands were determined, a statistically significant bias in the removal of ethyl-induced, alkali-labile sites was observed, with clearance occurring 30% faster from the transcribed strand than from its nontranscribed counterpart at early times after exposure. In contrast, removal of N-ethylpurines was observed in the dihydrofolate reductase locus in cells that lacked nucleotide excision repair, but both strands were repaired at the same rate, indicating that transcription-coupled clearance of these lesions requires the presence of active nucleotide excision repair.

Overproduction of dihydrofolate reductase and gene amplification in methotrexate-resistant Chinese hamster ovary cells

1982 ◽  
Vol 2 (3) ◽  
pp. 275-285
Author(s):  
W F Flintoff ◽  
M K Weber ◽  
C R Nagainis ◽  
A K Essani ◽  
D Robertson ◽  
...  
Keyword(s):  
Dihydrofolate Reductase ◽  
Chinese Hamster Ovary ◽  
Selection Process ◽  
Chinese Hamster Ovary Cells ◽  
Cdna Probe ◽  
Chinese Hamster ◽  
Wild Type Enzyme ◽  
Ovary Cells ◽  
Reductase Gene ◽  
Elevated Rate

Stable isolates of Chinese hamster ovary cells that are highly resistant to methotrexate have been selected in a multistep selection process. Quantitative immunoprecipitations have indicated that these isolates synthesize dihydrofolate reductase at an elevated rate over its synthesis in sensitive cells. Restriction enzyme and Southern blot analyses with a murine reductase cDNA probe indicate that the highly resistant isolates contain amplifications of the dihydrofolate reductase gene number. Depending upon the parenteral line used to select these resistant cells, they overproduce either a wild-type enzyme or a structurally altered enzyme. Karyotype analysis shows that some of these isolates contain chromosomes with homogeneously staining regions whereas others do not contain such chromosomes.

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