Dynamic human MutSα–MutLα complexes compact mismatched DNA

• Published in: Proceedings of the National Academy of Sciences - PNAS 2020-07, Vol.117 (28), p.16302-16312
• Main Authors: Bradford, Kira C., Wilkins, Hunter, Hao, Pengyu, Li, Zimeng M., Wang, Bangchen, Burke, Dan, Wu, Dong, Smith, Austin E., Spaller, Logan, Du, Chunwei, Gauer, Jacob W., Chan, Edward, Hsieh, Peggy, Weninger, Keith R., Erie, Dorothy A.
• Format: Article
• Language: English
• Subjects: Adenosine triphosphate; Adenosine Triphosphate - metabolism; Antigens; Atomic force microscopy; ATP; Biological Sciences; Compacting; Deoxyribonucleic acid; DNA; DNA - chemistry; DNA - genetics; DNA - metabolism; DNA biosynthesis; DNA Mismatch Repair; DNA repair; DNA-Binding Proteins - chemistry; DNA-Binding Proteins - metabolism; Eukaryotes; Humans; Mismatch repair; Multiprotein Complexes - metabolism; Mutation; MutL Proteins - chemistry; MutL Proteins - metabolism; MutS Homolog 2 Protein - chemistry; MutS Homolog 2 Protein - metabolism; Nicking endonuclease; Nucleic Acid Conformation; Nucleosomes; Nucleosomes - metabolism; Proliferating cell nuclear antigen; Protein Folding; Protein Multimerization; Proteins; Repair; Replication; Stoichiometry; Structure-function relationships; Time dependence
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.1918519117

DNA mismatch repair (MMR) corrects errors that occur during DNA replication. In humans, mutations in the proteins MutSα and MutLα that initiate MMR cause Lynch syndrome, the most common hereditary cancer. MutSα surveilles the DNA, and upon recognition of a replication error it undergoes adenosine triphosphate-dependent conformational changes and recruits MutLα. Subsequently, proliferating cell nuclear antigen (PCNA) activates MutLα to nick the error-containing strand to allow excision and resynthesis. The structure–function properties of these obligate MutSα–MutLα complexes remain mostly unexplored in higher eukaryotes, and models are predominately based on studies of prokaryotic proteins. Here, we utilize atomic force microscopy (AFM) coupled with other methods to reveal time- and concentration-dependent stoichiometries and conformations of assembling human MutSα–MutLα–DNA complexes.We find that they assemble into multimeric complexes comprising three to eight proteins around a mismatch on DNA. On the timescale of a few minutes, these complexes rearrange, folding and compacting the DNA. These observations contrast with dominant models of MMR initiation that envision diffusive MutS–MutL complexes that move away from the mismatch. Our results suggest MutSα localizes MutLα near the mismatch and promotes DNA configurations that could enhance MMR efficiency by facilitating MutLα nicking the DNA at multiple sites around the mismatch. In addition, such complexes may also protect the mismatch region from nucleosome reassembly until repair occurs, and they could potentially remodel adjacent nucleosomes.