Mi-2/NuRD: multiple complexes for many purposes.

The vertebrate Mi-2/NuRD complex is a multi-subunit protein complex containing both histone deacetylase and nucleosome-dependent ATPase subunits. Current models predict that this complex functions primarily in transcriptional repression. Surprisingly, every subunit of this complex presents heterogeneity at the protein and gene level. This raises the intriguing possibility of functional specialization resulting from incorporation of unique gene products into the complex. The MTA (metastasis-associated) proteins represent one class of alternative subunits of the human Mi-2/NuRD complex. The members of this family in human cells are differentially expressed depending on cell type and on physiologic parameters. We summarize evidence supporting the view that the alternative subunits of the complex that have arisen during vertebrate evolution endow unique functional properties.