Antigen Structural Requirements for Recognition by a Cyclobutane Thymine Dimer-Specific Monoclonal Antibody

A monoclonal antibody (TDM-2) specific to a UV-induced cyclobutane pyrimidine dimer (T[c/s-syn]T) has previously been established; however, the immunization had used UV-irradiated calf-thymus DNA containing a heterogeneous mixture of photoproduct sites. We investigated here the structural requirements of antigen recognition by the antibody using chemically synthesized antigen analogs. TDM-2 bound with cis-syn, but not trans-syn thymine dimer, and could bind strongly with four nucleotide analogs in which the cis-syn pyrimidine dimer was located in the center. Antigen analogs containing abasic linkers at the 5′- or 3′-side of the cis-syn cyclobutane pyrimidine dimer were synthesized and tested for binding to TDM-2. The results indicated that TDM-2 recognizes not only the cyclobutane ring but also both the 5′- and 3′-side nucleosides of the cyclobutane dimer. Furthermore, it was proved that either the 5′- or 3′-side phosphate group at a cyclobutane dimer site was absolutely required for the affinity to TDM-2. The antibody showed a strong binding to single stranded DNA but indicated little binding to double stranded DNA.