Solution structure of the DNA decamer duplex containing a 3'-T x T basepair of the cis-syn cyclobutane pyrimidine dimer: implication for the mutagenic property of the cis-syn dimer.
The cis - syn dimer is the major DNA photoproduct produced by UV irradiation. In order to determine the origin of the mutagenic property of the cis - syn dimer, we used NMR restraints and molecular dynamics to determine the solution structure of a DNA decamer duplex containing a wobble pair between the 3'-T of the cis - syn dimer and the opposite T residue (CS/TA duplex). The solution structure of the CS/TA duplex revealed that the 3'-T x T base pair of the cis - syn dimer had base pair geometry that was significantly different from the canonical Watson-Crick base pair and caused destabilization and conformational distortion of its 3'-region. However, a 3'-T x A base pair at the cis - syn dimer within this related DNA decamer maintains the normal Watson-Crick base pair geometry and causes little distortion in the conformation of its 3'-side. Our results show that in spite of its stable hydrogen bonding, the insertion of a T residue opposite the 3'-T of the cis - syn dimer is inhibited by structural distortion caused by the 3'-T x T base pair. This may explain why the frequency of the 3'-T-->A transversion, which is the major mutation produced by the cis - syn dimer, is only 4%.
Lee
J H
JH
Department of Chemistry and School of Molecular Science (BK21), Korea Advanced Institute of Science and Technology, 373-1 Kusong-dong, Yusong-gu, Taejon 305-701, Korea.
Choi
Y J
YJ
Choi
B S
BS
D020029:Base Pairing; D004247:DNA / Q000737:chemistry*; D019281:Dimerization; D009682:Magnetic Resonance Spectroscopy; D009153:Mutagens; D009690:Nucleic Acid Conformation; D011740:Pyrimidine Dimers / Q000737:chemistry*; D012996:Solutions
D009153:Mutagens; D011740:Pyrimidine Dimers; D012996:Solutions; D004247:DNA