The sensitization of cells treated with O6-methylguanine to alkylation damage is affected by the number of O6-methylguanine-DNA methyltransferase molecules escaped from inactivation.
O6-Methylguanine (MeG) can bind to the active site of O6-methylguanine-DNA methyltransferase (MGMT) as a free base. The subsequent methyl transfer reaction inactivates the repair protein. Hence, MeG is used to deplete the active MGMT pools in Chinese hamster cell lines (CHO) transfected to express varying amounts of human MGMT. After treatment with the free base, a residual population of active protein molecules remains localized mostly in the cytoplasm. Depleted cells are then challenged with the alkylating drug mitozolomide. Genotoxicity of this agent varied among the cell lines, and the compound sensitivity seemed to be regulated by a steady state equilibrium of residual MGMT molecules between nucleus and cytoplasm.
Citti
L
L
Genetica e Biochimica Tossicologica, CNR-Istituto di Mutagenesi e Differenziamento, Pisa, Italy.
Mariani
L
L
Capecchi
B
B
Piras
A
A
Leuzzi
R
R
Rainaldi
G
G
D000818:Animals; D016466:CHO Cells; D020134:Catalytic Domain; D006224:Cricetinae; D004305:Dose-Response Relationship, Drug; D006147:Guanine / Q000031:analogs & derivatives* / Q000494:pharmacology; D006801:Humans; D009153:Mutagens / Q000633:toxicity*; D009588:Nitrogen Mustard Compounds / Q000633:toxicity*; D019853:O(6)-Methylguanine-DNA Methyltransferase / Q000187:drug effects* / Q000235:genetics; D011994:Recombinant Proteins / Q000187:drug effects
D009153:Mutagens; D009588:Nitrogen Mustard Compounds; D011994:Recombinant Proteins; D006147:Guanine; C008449:O-(6)-methylguanine; C040369:mitozolomide; D019853:O(6)-Methylguanine-DNA Methyltransferase