Characterization of the "mismatch repairosome" and its role in the processing of modified nucleosides in vitro.

The process of postreplicative mismatch repair (MMR) increases the fidelity of DNA replication by eliminating biosynthetic errors from newly synthesized DNA. In addition, MMR proteins are also involved in the processing of intermediates of mitotic and meiotic recombination and, in mammalian cells, play a role in DNA damage signaling. As mismatches cannot be induced in the DNA of living cells, the study of the molecular transactions during MMR is restricted to in vitro systems. This chapter describes the construction of heteroduplex substrates that can be used for DNA affinity purification of MMR protein complexes and for the study of the role of eukaryotic MMR proteins in the processing of modified nucleosides.