Multifaceted roles of alkyltransferase and related proteins in DNA repair, DNA damage, resistance to chemotherapy, and research tools

Chem Res Toxicol. 2011 May 16;24(5):618-39. doi: 10.1021/tx200031q. Epub 2011 Apr 28.


O(6)-Alkylguanine-DNA alkyltransferase (AGT) is a widely distributed, unique DNA repair protein that acts as a single agent to directly remove alkyl groups located on the O(6)-position of guanine from DNA restoring the DNA in one step. The protein acts only once, and its alkylated form is degraded rapidly. It is a major factor in counteracting the mutagenic, carcinogenic, and cytotoxic effects of agents that form such adducts including N-nitroso-compounds and a number of cancer chemotherapeutics. This review describes the structure, function, and mechanism of action of AGTs and of a family of related alkyltransferase-like proteins, which do not act alone to repair O(6)-alkylguanines in DNA but link repair to other pathways. The paradoxical ability of AGTs to stimulate the DNA-damaging ability of dihaloalkanes and other bis-electrophiles via the formation of AGT-DNA cross-links is also described. Other important properties of AGTs include the ability to provide resistance to cancer therapeutic alkylating agents, and the availability of AGT inhibitors such as O(6)-benzylguanine that might overcome this resistance is discussed. Finally, the properties of fusion proteins in which AGT sequences are linked to other proteins are outlined. Such proteins occur naturally, and synthetic variants engineered to react specifically with derivatives of O(6)-benzylguanine are the basis of a valuable research technique for tagging proteins with specific reagents.

Publication types

  • Research Support, N.I.H., Extramural
  • Review

MeSH terms

  • Amino Acid Sequence
  • Animals
  • DNA / genetics*
  • DNA / metabolism
  • DNA Damage*
  • DNA Repair*
  • Drug Resistance, Neoplasm
  • Humans
  • Models, Molecular
  • Molecular Sequence Data
  • Neoplasms / drug therapy
  • Neoplasms / enzymology*
  • O(6)-Methylguanine-DNA Methyltransferase / chemistry
  • O(6)-Methylguanine-DNA Methyltransferase / genetics
  • O(6)-Methylguanine-DNA Methyltransferase / metabolism*
  • Sequence Alignment


  • DNA
  • O(6)-Methylguanine-DNA Methyltransferase