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Apparent lack of an O/sup 6/-methylguanine repair mechanism in the unicellular alga, Chlamydomonas ReinhardtII

Journal Article · · Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States)
OSTI ID:5118561
;
O/sup 6/-Methylguanine (O/sup 6/meG) is the presumed major mutagenic lesion formed by the treatment of DNA with methylating agents such as N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). The repair of this lesion has been shown to involve a protein which selectively removes the O/sup 6/-methyl group by transferring the group to one of the protein's cysteinyl residues. Several prokaryotic and eukaryotic organisms have this O/sup 6/-meG transferase (O/sup 6/MGT) activity, while other (e.g., yeast) lack any apparent O/sup 6/MGT. In some organisms, the O/sup 6/MGT is inducible in response to sublethal doses of methylating agent. The authors have examined Chlamydomonas for such a repair system. This is the first report of a search for O/sup 6/meG repair in a plant system. O/sup 6/meG repair was examined on three levels: in vivo removal of O/sup 6/meG, inducible repair of O/sup 6/meG, the presence of O/sup 6/MGT activity in cellular extracts. They observed no obvious removal of O/sup 6/meG from cellular DNA at various times (up to 30 hours) after treatment of cells with MNNG. The authors were unable to detect any inducible repair of O/sup 6/meG upon pretreatment of cells with sublethal doses of MNNG. Finally, they observed no apparent O/sup 6/MGT activity in cell-free extracts prepared two different ways following the protocols used in E. coli and in rat liver. These results suggest Chlamydomonas apparently lacks a repair mechanism for O/sup 6/meG.
Research Organization:
Univ. of South Dakota, Vermillon
OSTI ID:
5118561
Report Number(s):
CONF-8606151-
Journal Information:
Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States), Journal Name: Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States) Vol. 45:6; ISSN FEPRA
Country of Publication:
United States
Language:
English

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Related Subjects

560302* -- Chemicals Metabolism & Toxicology-- Microorganisms-- (-1987)
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
ALGAE
AMINES
AROMATICS
AZAARENES
BIOLOGICAL EFFECTS
BIOLOGICAL RECOVERY
BIOLOGICAL REPAIR
CHLAMYDOMONAS
DNA
DNA REPAIR
ENZYME ACTIVITY
ENZYMES
GENETIC EFFECTS
GUANINE
HETEROCYCLIC COMPOUNDS
HYDROXY COMPOUNDS
MICROORGANISMS
NITROSO COMPOUNDS
NUCLEIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PLANTS
PURINES
RECOVERY
REPAIR
TRANSFERASES
UNICELLULAR ALGAE