INO80-C and SWR-C: Guardians of the Genome

The double membrane of the eukaryotic nucleus surrounds the genome, constraining it to a nuclear sphere. Proteins, RNA protein particles and artificial chromosome rings diffuse rapidly and freely throughout the nucleoplasm, while chromosomal loci show subdiffusive movement with varying degrees of constraint. In situ biochemical approaches and live imaging studies have revealed the existence of nuclear subcompartments that are enriched for specific chromatin states and/or enzymatic activities. This sequestration is thought to enhance the formation of heterochromatin, particularly when factors of limited abundance are involved. Implicit in the concept of compartmentation is the idea that chromatin is able to move from one compartment to another. Indeed, in budding yeast, gene activation, repression and the presence of persistent DNA double-strand breaks each has been shown to provoke subnuclear relocalization of chromatin. In some cases, movement has been linked to the action of ATP-dependent chromatin remodeling complexes, more specifically to the Snf2-related ATPase-containing complexes, SWR-C and INO80-C. Here we examine how these multi-subunit remodelers contribute to chromatin-based processes linked to the DNA damage response. We review recent evidence that supports a role for yeast SWR-C and INO80-C in determining the subnuclear position of damaged domains and finally, we recap the multiple ways in which these remodelers contribute to genomic integrity.