New structures of MutS bound to DNA replication structures: a change to gain access to the replisome

Congreso; LIV Reunión Anual de SAIB; 2018

MutS contributes to the DNA replication fidelity by recognizing mispairs (MMs) and recruiting factors involved in the Mismatch Repair (MMR). We have revealed a non-canonical function of MutS in the replication machinery: the regulation of the access of the mutagenic DNA polymerase (Pol) IV to replication sites. Our previous results indicated that DNA substrates (single-stranded, homoduplex, heteroduplex, primed and GT-primed DNAs) modulate the ability of MutS to regulate the Pol IV action. Here, we examined the effect of these DNA substrates on the structure and biochemical properties of MutS. The replication substrate GT-primed DNA, but not the other DNA structures, specifically induced a compaction of MutS. When we tested primed-DNAs containing the 12 different types of MMs, the CC, GG and GA produced also the structural MutS compaction. This agrees with the fact that Pol IV predominantly generates these MMs when copying DNA. We also characterized the properties important for the repair pathway initiated by MutS, namely the ATPase activity, MutL interaction and stimulation the MutL-endonuclease activity, in the presence of the DNA substrates. In addition, we are testing if the structural change induced by the replication substrate GT-primed DNA is necessary for MutS gaining access to the replisome. Thus, this work reveals that complex protein-DNA interactions could dictate the function of MutS in a particular pathway, repair or regulation of the access of Pol IV.