Figure 2. Roles for chromatin packing in auxin-mediated transcriptional response.
Under low auxin conditions, Aux/IAA proteins are abundant and interact with ARF proteins. Aux/IAAs recruit the TOPLESS (TPL) family of corepressors, which in turn recruit Histone deacetylases (HDACs), resulting in tightly packed chromatin. Furthermore, Aux/IAA proteins likely block the interaction between ARF and SWI/SNF chromatin remodeling complexes. When auxin levels are elevated, Aux/IAA proteins are targeted for proteasomal degradation, allowing for SWI/SNF interaction with ARF proteins. SWI/SNF-enabled chromatin remodeling, through histone acetyltransferase (HAT) activity, results in chromatin unpacking to allow gene target access by additional transcription factors.