Monomers through trimers of large tumor antigen bind in region I and monomers through tetramers bind in region II of simian virus 40 origin of replication DNA as stable structures in solution.

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Abstract
Large tumor (T) antigen and its bound multimeric states are positioned by scanning transmission electron microscopy (STEM) within a few baes pairs at control sequences of the SV40 DNA origin of replication region. Proximal and distal edge positions for each multimer group match the end positions of previously mapped fragments protected from DNase cleavage. Since chance correspondence is shown to be extremely unlikely, STEM mass measurements, obtained concurrently with STEM map positions, indicate that the DNase fragments arise from bound monomers, dimers, and trimers in binding region I. Simultaneous binding of 7 monomer-equivalent masses is observed, 3 in region I and 4 in region II, with an ordered and interpretable mass distribution in the plane of the foil. Although this observation does not prove that the 6 G-A-G-G-C and 1 T-A-G-G-C sequences, similarly distributed, function as recognition sequences for T-antigen monomer, it provides strong support for such a model. The stable existence in solution of low- and intermediate-mass structures, observed at lower T-antigen concentrations, suggests a role as assembly intermediates.