Book of Abstracts: Albany 2003
June 17-21 2003
Exploring the DNA Structure Preferences of Human O6-Alkylguanine-DNA Alkyltransferase (AGT)
Human O6-Alkylguanine-DNA alkyltransferase (AGT) repairs DNA by a single-step transfer of an alkyl group from the 6-position on guanine to a cysteine residue in the active site of the protein. The guanine is regenerated, but the cysteine remains irreversibly alkylated. The modified protein is repair-deficient and is degraded, probably after ubiquitinylation. This repair process is preceded by DNA binding events in order for the protein to effectively search the genome for alkyl lesions. In vitro studies indicate that the apparent binding constants of the protein for different lengths and forms of DNA are relatively similar. The protein binds DNA, both short stretches and plasmid-sized fragments, in a positively cooperative manner. However, using short DNA fragments, it is readily seen that kinetics of binding depends on whether the DNA is in single-stranded or in double-stranded form. The mechanism, by which AGT distinguishes different forms of DNA including histone-associated states, is being investigated.
Sambit R. Kar1,2
1Dept of Cell. & Mol. Physiology