ABSTRACT
DNA mismatch repair (MMR) maintains genome stability through repair of DNA replication errors. In Escherichia coli, initiation of MMR involves recognition of the mismatch by MutS, recruitment of MutL, activation of endonuclease MutH and DNA strand incision at a hemimethylated GATC site. Here, we studied the mechanism of communication that couples mismatch recognition to daughter strand incision. We investigated the effect of catalytically-deficient Cas9 as well as stalled RNA polymerase as roadblocks placed on DNA in between the mismatch and GATC site in ensemble and single molecule nanomanipulation incision assays. The MMR proteins were observed to incise GATC sites beyond a roadblock, albeit with reduced efficiency. This residual incision is completely abolished upon shortening the disordered linker regions of MutL. These results indicate that roadblock bypass can be fully attributed to the long, disordered linker regions in MutL and establish that communication during MMR initiation occurs along the DNA backbone.
Subject(s)
DNA Mismatch Repair/genetics , DNA, Bacterial/genetics , Deoxyribonucleases, Type II Site-Specific/metabolism , Escherichia coli Proteins/metabolism , Escherichia coli/genetics , MutL Proteins/metabolism , Base Pair Mismatch/genetics , CRISPR-Associated Protein 9/genetics , DNA Repair Enzymes/metabolism , DNA-Binding Proteins/metabolism , DNA-Directed RNA Polymerases/genetics , Endodeoxyribonucleases/metabolism , Genomic Instability/genetics , MutS DNA Mismatch-Binding Protein/metabolismABSTRACT
In this issue of Structure, Cho and colleagues provide intriguing insight into the first steps of the DNA mismatch repair process. By using single-molecule techniques, they show that the protein MutS undergoes two different types of diffusion on error-containing DNA in an ATP-dependent way.
Subject(s)
Adenosine Triphosphate/chemistry , Bacterial Proteins/chemistry , DNA/chemistry , MutS DNA Mismatch-Binding Protein/chemistry , Thermus/chemistrySubject(s)
DNA Helicases/chemistry , DNA Helicases/metabolism , DNA, Bacterial/metabolism , Escherichia coli Proteins/chemistry , Escherichia coli Proteins/metabolism , Escherichia coli/chemistry , Membrane Proteins/chemistry , Membrane Proteins/metabolism , Chromosomes, Bacterial , Escherichia coli/enzymology , Escherichia coli/genetics , Protein Structure, TertiaryABSTRACT
Single-molecule experiments show that the chromatin-remodeling complex RSC, a member of the SNF2 ATPase family, induces formation of a negatively supercoiled DNA loop by active translocation.
