Chemical synthesis and translesion replication of a cis–syn cyclobutane thymine–uracil dimer

AUTOR(ES)

Takasawa, Kohei

FONTE

Oxford University Press

RESUMO

The cytosine base in DNA undergoes hydrolytic deamination at a considerable rate when UV radiation induces formation of a cyclobutane pyrimidine dimer (CPD) with an adjacent pyrimidine base. We have synthesized a phosphoramidite building block of a cis–syn cyclobutane thymine–uracil dimer (T[]U), which is the deaminated form of the CPD at a TC site, and incorporated it into oligodeoxyribonucleotides. The previously reported method for synthesis of the thymine dimer (T[]T) was applied, using partially protected thymidylyl-(3′–5′)-2′-deoxyuridine as the starting material, and after triplet- sensitized irradiation, the configuration of the base moiety in the major product was determined by NMR spectroscopy. Presence of the cis–syn cyclobutane dimer in the obtained oligonucleotides was confirmed by UV photoreversal and reaction with T4 endonuclease V. Using a 30mer containing T[]U, translesion synthesis by human DNA polymerase η was analyzed. There was no difference in the results between the templates containing T[]T and T[]U and pol η bypassed both lesions with the same efficiency, incorporating two adenylates. This enzyme showed fidelity to base pair formation, but this replication causes a C→T transition because the original sequence is TC.

Documentos Relacionados

• Frequency and spectrum of mutations produced by a single cis-syn thymine-thymine cyclobutane dimer in a single-stranded vector.
• Crystal structure of a DNA decamer containing a cis-syn thymine dimer
• Essential dynamics of DNA containing a cis.syn cyclobutane thymine dimer lesion.
• Solution structure of the DNA decamer duplex containing a 3′-T·T base pair of the cis–syn cyclobutane pyrimidine dimer: implication for the mutagenic property of the cis–syn dimer
• Distinct mechanisms of cis-syn thymine dimer bypass by Dpo4 and DNA polymerase η