MutS-dependent regulation of the error-prone Pol IV action: DNA structures as key modulators

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

Córdoba

Congreso; LII Reunion Anual de SAIB; 2016

MI-P14MutS-DEPENDENT REGULATION OF THE ERROR-PRONE Pol IV ACTION: DNA STRUCTURES AS KEY MODULATORSMargara LM, Argaraña CE, Monti MR.CIQUIBIC-CONICET. Dpto. de Qca. Biol., FCQ-UNC, Córdoba. Argentina.E-mail: mmonti@mail.fcq.unc.edu.arTranslesion DNA polymerases (Pol) function in the bypass of template lesions to relieve stalled replication forks. Effective activity of these Pols requires association with ring-shaped processivity factors, which dictate their access to sites of DNA synthesis. We showed for the first time that the repair protein MutS regulates the access of the mutagenic Pol IV to replication sites. Our previous biochemical data revealed that MutS inhibits the Pol IV interaction with β clamp by competing for binding to a hydrophobic cleft on the ring. Here, we examined the effect of different DNA substrates (single-stranded, homoduplex, heteroduplex, primed and GT-primed DNAs) on the affinity of Pol IV? and MutS?β clamp interactions. Neither DNA substrates had a significant effect on the strength of the Pol IV?β clamp association. The presence of the GT-primed DNA enhanced the MutS?β clamp interaction and modified the MutS oligomeric state bound to β clamp. We also demonstrated that DNA structures modulate the effectiveness of MutS as a competitor for the Pol IV-β clamp interaction. MutS exerted a more strict control over Pol IV binding to β clamp in the presence of primed-DNAs whereas the single-stranded DNA abolished the capability of MutS for limiting the Pol IV-β clamp interaction. Thus, this work reveals that complex protein-DNA interactions are involved in this noncanonical function of MutS