The origin of O6-methylguanine-DNA methyltransferase in Chinese hamster ovary cells transfected with human DNA.
Published
Journal Article
Transfection of Chinese hamster ovary (CHO) cells with human DNA has been shown in several laboratories to produce clones which stably express the DNA-repair protein, O6-methylguanine-DNA methyltransferase (MGMT), that is lacking in the parent cell lines (Mex- phenotype). We have investigated the genetic origin of the MGMT in a number of such MGMT-positive (Mex+) clones by using human MGMT cDNA and anti-human MGMT antibodies as probes. None of the five independently isolated Mex+ lines has human MGMT gene sequences. Immunoblot analysis confirmed the absence of the human protein in the extracts of these cells. The MGMT mRNA in the lines that express low levels of MGMT (0.6-1.4 x 10(4) molecules/cell) is of the same size (1.1 kb) as that present in hamster liver. One cell line, GC-1, with a much higher level of MGMT (4 x 10(4) molecules/cell) has two MGMT mRNAs, a major species of 1.3 kb and a minor species of 1.8 kb. It has also two MGMT polypeptides (32 and 28 kDa), both of which are larger than the 25 kDa MGMT present in hamster liver and other Mex+ transfectants. These results indicate that the MGMT in all Mex+ CHO cell clones is encoded by the endogenous gene. While spontaneous activation of the MGMT gene cannot be ruled out in the Mex+ cell clones, the intervention of human DNA sequences may be responsible for activation of the endogenous gene in the GC-1 line.
Full Text
Duke Authors
Cited Authors
- Tano, K; Shiota, S; Remack, JS; Brent, TP; Bigner, DD; Mitra, S
Published Date
- September 1, 1991
Published In
Volume / Issue
- 255 / 2
Start / End Page
- 175 - 182
PubMed ID
- 1922149
Pubmed Central ID
- 1922149
International Standard Serial Number (ISSN)
- 0027-5107
Digital Object Identifier (DOI)
- 10.1016/0921-8777(91)90051-p
Language
- eng
Conference Location
- Netherlands