1174 Nucleic Acids Research, 2011, Vol. 39, No. 3
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stalled after incorporation of dAMP opposite the
30-component of the trans-syn CPD. Since the base orien-
tation of the 50-component is fixed in the SYN conform-
ation, there may be a steric hindrance when this lesion
enters the active site of the enzyme, and the 50-component
cannot make a base pair with the incoming nucleotide
even if it can fit the active site. This is an example
showing that the stereochemistry of a biomolecule
affects its biological property.
In conclusion, we investigated the cycloaddition
N-acetylated
reaction
between
thymine
and
5-methylcytosine, and found that the reaction proceeded
in a diastereoselective manner to yield the trans-syn CPD
with the SYN-ANTI conformation. In addition, the
acetylamino group was hydrolyzed more rapidly than
the unmodified amino group. These findings provided an
efficient method for the synthesis of oligonucleotides con-
taining this type of UV lesion. Further studies, including
experiments using other types of modifications, are
required to elucidate the mechanism that generates this
stereoselectivity.
SUPPLEMENTARY DATA
15. Su,D.G.T., Kao,J.L.-F., Gross,M.L. and Taylor,J.-S. (2008)
Structure determination of an interstrand-type cis-anti cyclobutane
thymine dimer produced in high yield by UVB light in an
oligodeoxynucleotide at acidic pH. J. Am. Chem. Soc., 130,
11328–11337.
Supplementary Data are available at NAR Online.
FUNDING
16. Su,D.G.T., Fang,H., Gross,M.L. and Taylor,J.-S. (2009)
Photocrosslinking of human telomeric G-quadruplex loops by anti
cyclobutane thymine dimer formation. Proc. Natl Acad. Sci. USA,
106, 12861–12866.
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21. Peng,W. and Shaw,B.R. (1996) Accelerated deamination of
cytosine residues in UV-induced cyclobutane pyrimidine dimers
leads to CC!TT transitions. Biochemistry, 35, 10172–10181.
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time-dependent deamination of cytosine bases in UVB-induced
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23. Takasawa,K., Masutani,C., Hanaoka,F. and Iwai,S. (2004)
Chemical synthesis and translesion replication of a cis-syn
cyclobutane thymine-uracil dimer. Nucleic Acids Res., 32,
1738–1745.
Research Fellowships of the Japan Society for the
Promotion of Science for Young Scientists from the
Ministry of Education, Culture, Sports, Science and
Technology, Japan (to J.Y.) Funding for open access
charge: Management expenses grants from the Ministry
of Education, Culture, Sports, Science and Technology,
Japan.
Conflict of interest statement. None declared.
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