Expression of human O6-methyl guanine methyl transferase (MGMT) in post replication repair (PRR) deficient CHO-UV-1 cells: compensation for hypersensitivity to methylating and ethylating agents but not to mitomycin C.
The cDNA for human MGMT was transfected into and expressed in CHO cells and the post-replication repair deficient mutant CHO-UV-1 cell, both of which are devoid of endogenous MGMT activity. Expression of MGMT activity was demonstrated by measurement of activity and by immunoblot analysis. The mutant phenotype of UV-1 is characterized by extreme hypersensitivity to killing by methylating and ethylating agents as well as the antitumor antibiotic mitomycin C (MMC). MGMT expression conferred equivalent, supra-normal levels of resistance to killing by MNNG (N-methyl-N'-nitro-nitrosoguanidine) or EMS (ethyl methanesulfonate) on CHO and UV-1, but had no effect on the lethality of MMC. So, even though a mutated gene other than MGMT is known to underlie the pleiotropic phenotype of UV-1, expression of MGMT compensates for part of this phenotype. This result indicates that attempts to concordance map and clone the gene(s) responsible for the UV-1 phenotype can be complicated when using MNNG selection due to compensation by the MGMT gene. These results also indicate that the post-replication repair deficient phenotype characterized in CHO-UV-1 cells, will be masked in cells normally expressing MGMT due to MGMT-mediated resistance to methylating and ethylating agents.
Gustafson
D L
DL
Department of Radiological Health Sciences, Colorado State University, Fort Collins 80521, USA.
Trotter
B K
BK
Snead
D
D
Waldren
C A
CA
D000477:Alkylating Agents / Q000494:pharmacology; D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D019175:DNA Methylation; D004260:DNA Repair; D005020:Ethyl Methanesulfonate / Q000494:pharmacology; D006801:Humans; D008769:Methylnitronitrosoguanidine / Q000633:toxicity; D008780:Methyltransferases / Q000378:metabolism*; D016685:Mitomycin / Q000494:pharmacology; D019853:O(6)-Methylguanine-DNA Methyltransferase
D000477:Alkylating Agents; D008769:Methylnitronitrosoguanidine; D016685:Mitomycin; D005020:Ethyl Methanesulfonate; D008780:Methyltransferases; D019853:O(6)-Methylguanine-DNA Methyltransferase