Structural and functional analysis of the SET3 histone deacetylase complex.

The SET3 complex (SET3C) is a seven-subunit histone deacetylase complex that is capable of transcriptional regulation. Methylated histone 3 marks recruit SET3C to the nucleosome, and the SET3C catalytic subunits deacetylate the histone 3 and 4 tails. There is very limited structural knowledge of the SET3C subunits, with most subunits having unknown structures or functions. Here, a catalytically active SET3 complex was endogenously purified from Saccharomyces cerevisiae and utilized for negative-stain electron microscopy (EM) to determine an apo model for the holo complex. The negative-stain EM 3D model revealed a three-lobe architecture, with each lobe extending from a central point.