Question

Molecular biology of the gene. From the paper “DNA repair mechanisms and the bypass of DNA damage in saccaromyces cerevisiae”

3. In general for methyltransferase a. b. What type of damage does it repair? How does it repair the damage? lanhy the damaged guanine woulr hymine nstead of eyriosine

Answer 1

The yeast methyltransferase protein, repairs both types of damages

The mispairing of O⁶-methylguanine (O⁶-MeG) with T and O⁴-methylthymine (O⁴-MeT) with G gives rise to GC-to-AT and AT-to-GC transitions, respectively.

methyltransferase repairs O⁶-MeG by a suicide reaction that irreversibly transfers the methyl group to a cysteine residue in the enzyme active site to generate S-methylcysteine. However the protein has much lower affinity for O⁴-MeT than for O⁶-MeG in vitro, O⁴MeT repair in vivo can be inferred because expression of methyltransferase in E. coli prevents methylation-associated AT-to-GC transitions.