Poster abstracts
Poster number 110 submitted by Kristin Chesnutt
ATAC and SAGA histone acetyltransferase modules facilitate transcription factor binding to nucleosomes in an acetylation independent manner
Kristin Chesnutt (Department of Physics, Ohio State University, Columbus, USA), Gizem Yayli (Institut de Gntique et de Biologie Molculaire et Cellulaire, Illkirch, France), Christine Toelzer (Bristol University, Bristol, UK), Imre Berger (Bristol University, Bristol, UK), Lszl Tora (Institut de Gntique et de Biologie Molculaire et Cellulaire, Illkirch, France), Michael G. Poirier (Department of Physics, Ohio State University, Columbus, USA)
Abstract:
Post translational modifications (PTMs) play a crucial role in transcription regulation by recruiting regulatory complexes and by assisting in the modulation of DNA accessibility to transcription factors (TFs). Human Spt-Ada-Gcn5-acetyltransferase (SAGA) and ADA-two-A-containing (ATAC) are two distinct multifunctional co-activator protein complexes that contain similar histone acetyltransferase (HAT) modules. SAGA and ATAC can be targeted to genomic loci through interactions with histone PTMs and TFs. The mechanism in which SAGA and ATAC function with TFs to target and acetylate nucleosomes remains unknown. Here we used Fluorescence Anisotropy (FA) to characterize human SAGA and ATAC HAT module interactions with nucleosomes. Fluorescence resonance energy transfer (FRET) was used to investigate how SAGA and ATAC HAT modules function with a TF (Gal4-VP16 and -DBD) to target nucleosomes. Additionally, Western blot assays were carried out to determine the influence TFs have on the acetylation activity of SAGA and ATAC HAT modules. We find that HAT modules of SAGA and ATAC bind with high affinity to nucleosomes, independent of TFs or PTMs. We also find that the SAGA and ATAC HAT modules can facilitate Gal4- VP16 and DBD invasion into nucleosomes independent of acetylation. Finally, we determined that Gal4-VP16 significantly enhances histone acetylation for both the SAGA and ATAC HAT modules. This data is evidence for a new function of SAGA and ATAC HAT modules, displaying an ability to facilitate TF binding to nucleosomes that is acetylation independent.
Keywords: lysine acetylation, transcription regulation, nucleosome