1N14

Structure and Dynamics of Thioguanine-modified Duplex DNA in Comparison with Unmodified DNA; Structure of Unmodified Duplex DNA

Summary for 1N14

• Entry DOI: 10.2210/pdb1n14/pdb
• Related: 1N17
• Descriptor: 5'-D(*GP*CP*TP*AP*AP*GP*GP*AP*AP*AP*GP*CP*C)-3', 5'-D(*GP*GP*CP*TP*TP*TP*CP*CP*TP*TP*AP*GP*C)-3' (2 entities in total)
• Functional Keywords: mercaptopurine, thioguanine, anti-cancer therapy, dna
• Total number of polymer chains: 2
• Total formula weight: 7943.19

Authors

Somerville, L.,Krynetski, E.Y.,Krynetskaia, N.F.,Beger, R.D.,Zhang, W.,Marhefka, C.A.,Evans, W.E.,Kriwacki, R.W. (deposition date: 2002-10-16, release date: 2002-10-23, Last modification date: 2024-05-22)

Primary citation

Somerville, L.,Krynetski, E.Y.,Krynetskaia, N.F.,Beger, R.D.,Zhang, W.,Marhefka, C.A.,Evans, W.E.,Kriwacki, R.W.
Structure and dynamics of thioguanine-modified duplex DNA
J.Biol.Chem., 278:1005-1011, 2003

PubMed Abstract: Mercaptopurine and thioguanine, two of the most widely used antileukemic agents, exert their cytotoxic, therapeutic effects by being incorporated into DNA as deoxy-6-thioguanosine. However, the molecular mechanism(s) by which incorporation of these thiopurines into DNA translates into cytotoxicity is unknown. The solution structure of thioguanine-modified duplex DNA presented here shows that the effects of the modification on DNA structure were subtle and localized to the modified base pair. Specifically, thioguanine existed in the keto form, formed weakened Watson-Crick hydrogen bonds with cytosine and caused a modest approximately 10 degrees opening of the modified base pair toward the major groove. In contrast, thioguanine significantly altered base pair dynamics, causing an approximately 80-fold decrease in the base pair lifetime with cytosine compared with normal guanine. This perturbation was consistent with the approximately 6 degrees C decrease in DNA melting temperature of the modified oligonucleotide, the 1.13 ppm upfield shift of the thioguanine imino proton resonance, and the large increase in the exchange rate of the thioguanine imino proton with water. Our studies provide new mechanistic insight into the effects of thioguanine incorporation into DNA at the level of DNA structure and dynamics, provide explanations for the effects of thioguanine incorporation on the activity of DNA-processing enzymes, and provide a molecular basis for the specific recognition of thioguanine-substituted sites by proteins. These combined effects likely cooperate to produce the cellular responses that underlie the therapeutic effects of thiopurines.

PubMed: 12401802
DOI: 10.1074/jbc.M204243200

Experimental method

SOLUTION NMR