MUS81 Endonuclease Homolog (MUS81)

MUS81 has associated endonuclease activity against structure-specific oligonucleotide substrates, including synthetic Holliday junctions. MUS81-associated endonuclease resolved Holliday junctions into linear duplexes by cutting across the junction exclusively on strands of like polarity. In addition, MUS81 protein abundance increased in cells following exposure to agents that block DNA replication. Taken together, these findings suggested a role for MUS81 in resolving Holliday junctions that arise when DNA replication is blocked by damage or by nucleotide depletion. The authors stated that MUS81 is not related by sequence to previously characterized Holliday junction-resolving enzymes, and it has distinct enzymatic properties that suggest it uses a novel enzymatic strategy to cleave Holliday junctions.