Department of Biochemistry, Biophysics and Molecular Biology - Iowa State University

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Host:  Michael Shogren-Knaak

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"Effects of a Transcriptional Activator on SAGA Histone Acetyltransferase Activity"

Eukaryotic gene expression requires the coordination of multiple factors to overcome the repressive nature of chromatin.  In chromatin, genomic DNA is wrapped around a spool of histone proteins forming a nucleosome, the basic unit of chromatin.  Histone proteins have two domains – a structured core domain and an unstructured tail domain.  One primary method in alleviating the repressive nature of chromatin is the addition of post-translational modifications to the histone tails.  These marks are established by the recruitment of coactivator complexes to the chromatin by DNA-binding proteins called activators.  One coactivator which promotes the gene expression in eukaryotes is the histone modifying complex called SAGA.

Though many of the proteins and protein complexes involved in eukaryotic gene expression have been identified, mechanistic knowledge about how the proteins interact with and influence one another to promote gene expression remains limited.  In this work, we have started to tease out the effects of an activator protein on the HAT activity of SAGA.  Altogether, the work presented suggests a model where SAGA binds to and acetylates nucleosomes inefficiently until it interacts with DNA-bound activators near gene promoters.  The interaction between activator and SAGA stimulates its HAT activity, thereby generating localized regions of hyperacetylation at gene promoters.

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