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

ARGARAÑA CARLOS E.; IBÁÑEZ MILAGROS; MONTI MARIELA R; MARGARA LUCÍA M

Paraná, Entre Rios

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-canonicalfunction of MutS in the replication machinery: the regulationof the access of the mutagenic DNA polymerase (Pol) IV to replication sites. Ourprevious results indicated that DNA substrates (single-stranded, homoduplex, heteroduplex, primed andGT-primed DNAs) modulate theability of MutS to regulate the Pol IV action. Here, we examined the effect of these DNAsubstrates on the structure and biochemical properties of MutS. The replicationsubstrate GT-primed DNA, but not the other DNA structures, specifically induceda compaction of MutS. When we tested primed-DNAs containing the 12different types of MMs, theCC, GG and GA produced also the structural MutS compaction. This agrees withthe fact that Pol IV predominantly generates these MMs whencopying DNA. We also characterizedthe properties important for the repair pathway initiated by MutS, namely the ATPaseactivity, MutL interaction and stimulation the MutL-endonuclease activity, inthe presence of the DNA substrates. In addition, we are testing if thestructural change induced by the replication substrate GT-primed DNA isnecessary for MutS gaining access to the replisome. Thus, this work reveals that complexprotein-DNA interactions could dictate the function of MutS in a particularpathway, repair or regulation of the access of Pol IV.