Chromatin architecture is very important for the regulation of transcriptional activation, Here, we investigated the role of two different chromatin components, the histone variant H2A.Z and HMG proteins Nhp6a/b, in regulating GAL1 gene expression. We have shown that recruitment of the Mediator complex is significantly affected in the absence of H2AZ Furthermore, H2A.Z is also required to fully recruit the SAGA and Swi/Snf complexes to the yeast GAL1-10 UAS(G). On the other hand, the HMG protein Nhp6a/b is not required to recruit the aforementioned components to the GAL1 promoter. The Nhp6 protein has been shown to interact with nucleosomes, and we show that its distribution is unaffected in the absence of H2AZ Our results suggest that the incorporation of the histone variant H2A.Z, but not the HMG proteins Nhp6a/b, in promoter regions creates a specialized chromatin domain that is required for pre-initiation complex assembly at the GAL1 locus. (C) 2008 Elsevier Inc. All rights reserved.