Poster abstracts
Poster number 93 submitted by Kristin Chesnutt
Evidence for an acetylation-independent function of the SAGA and ATAC human acetyltransferase modules
Kristin Chesnutt (OSBP, Ohio State University), Khan Cox (Department of Physics, Ohio State University), Christine Toelzer (School of Biochemistry, University of Bristol), Michael G. Poirier (Department of Physics, Ohio State University)
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. Förster 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. We also find that the SAGA HAT module can facilitate Gal4- VP16 and DBD invasion into nucleosomes, whereas the ATAC HAT module can facilitate VP16’s invasion into nucleosomes independent of acetylation. 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: chromatin, histone acetyltransferase, DNA accessibility