Mus81Mms4

Mus81Mms4 is a heterodimeric nuclease complex composed of the Mus81 and Mms4 proteins. This complex is a key player in DNA repair and genome stability in eukaryotes, particularly in yeast models. Its primary function is to resolve DNA structures that arise during replication and recombination, such as replication forks, Holliday junctions, and other cross-over structures.

The Mus81Mms4 complex is characterized by its ability to cleave specific DNA substrates. This cleavage activity is crucial for preventing the accumulation of toxic DNA intermediates that can lead to genomic instability and cell death. For example, during stalled replication forks, Mus81Mms4 can cleave the reversed fork structure, allowing for restart of replication. It also participates in the resolution of Holliday junctions, which are intermediates in homologous recombination.

The precise mechanisms and regulation of Mus81Mms4 activity are complex and still under investigation. It is thought to function in coordination with other DNA repair proteins. Genetic studies in organisms like Saccharomyces cerevisiae have highlighted the essential role of Mus81Mms4 in maintaining genome integrity. Mutations in the genes encoding these proteins often result in increased sensitivity to DNA damaging agents and a higher frequency of chromosomal aberrations. The presence of conserved homologues in various eukaryotic species suggests a fundamental importance for this nuclease in cellular processes.