Biomaterial Database

Repair of 3-methyladenine and 7-methylguanine in nuclear DNA of Chlamydomonas: requirement for protein synthesis. 1981

J M Sweet, and B Carda, and G D Small

The removal of 3-methyladenine and 7-methylguanine from nuclear DNA was determined following exposure of Chlamydomonas reinhardi to methyl methanesulfonate (MMS). The amount of 3-methyladenine in DNA was determined using an extract from Micrococcus luteus that has a 3-methyladenine-DNA glycosylase. The amount of 7-methylguanine was estimated by heating the DNA for 30 min at 70 degrees followed by alkaline hydrolysis of the resulting apurinic sites. The molecular weight of the DNA was determined using alkaline sucrose gradients. The 3-methyladenine is removed with a half-life of 2--3 h whereas the 7-methylguanine is removed with a half-life of 10--12 h. The rate of removal of the 7-methylguanine is more than an order of magnitude faster than the estimated non-enzymatic hydrolysis rate indicating the probability of enzymatic repair. Addition of cycloheximide immediately after MMS treatment inhibits the removal of 3-methyladenine and 7-methylguanine from DNA. If cycloheximide is added 1.5 h after treatment with MMS, there is much less inhibition of the removal of 3-methyladenine. These results are interpreted to mean that MMS induces the synthesis of 1 or more proteins that are required for the repair of 3-methyladenine from Chlamydomonas DNA.

UI	MeSH Term	Description	Entries
D008741	Methyl Methanesulfonate	An alkylating agent in cancer therapy that may also act as a mutagen by interfering with and causing damage to DNA.	Methylmethane Sulfonate,Dimethylsulfonate,Mesilate, Methyl,Methyl Mesylate,Methyl Methylenesulfonate,Methylmesilate,Mesylate, Methyl,Methanesulfonate, Methyl,Methyl Mesilate
D008970	Molecular Weight	The sum of the weight of all the atoms in a molecule.	Molecular Weights,Weight, Molecular,Weights, Molecular
D009153	Mutagens	Chemical agents that increase the rate of genetic mutation by interfering with the function of nucleic acids. A clastogen is a specific mutagen that causes breaks in chromosomes.	Clastogen,Clastogens,Genotoxin,Genotoxins,Mutagen
D002696	Chlamydomonas	A genus GREEN ALGAE in the order VOLVOCIDA. It consists of solitary biflagellated organisms common in fresh water and damp soil.	Chlamydomona
D004247	DNA	A deoxyribonucleotide polymer that is the primary genetic material of all cells. Eukaryotic and prokaryotic organisms normally contain DNA in a double-stranded state, yet several important biological processes transiently involve single-stranded regions. DNA, which consists of a polysugar-phosphate backbone possessing projections of purines (adenine and guanine) and pyrimidines (thymine and cytosine), forms a double helix that is held together by hydrogen bonds between these purines and pyrimidines (adenine to thymine and guanine to cytosine).	DNA, Double-Stranded,Deoxyribonucleic Acid,ds-DNA,DNA, Double Stranded,Double-Stranded DNA,ds DNA
D004260	DNA Repair	The removal of DNA LESIONS and/or restoration of intact DNA strands without BASE PAIR MISMATCHES, intrastrand or interstrand crosslinks, or discontinuities in the DNA sugar-phosphate backbones.	DNA Damage Response
D006151	Guanosine	A purine nucleoside that has guanine linked by its N9 nitrogen to the C1 carbon of ribose. It is a component of ribonucleic acid and its nucleotides play important roles in metabolism. (From Dorland, 28th ed)
D000225	Adenine	A purine base and a fundamental unit of ADENINE NUCLEOTIDES.	Vitamin B 4,4, Vitamin B,B 4, Vitamin