Chakraborty, D.Sandate, C.R.Isbel, L.Kempf, G.Weiss, J.Cavadini, S.Kater, L.Seebacher, J.Kozicka, Z.Stoos, L.Grand, R.S.Schübeler, D.Michael, A.K.Thomä, N.H.2025-10-212025-10-212025Molecular Cell, 2025; 85(15):2919-2936.e121097-27651097-4164https://hdl.handle.net/2440/147905Pioneer transcription factors (TFs) engage chromatinized DNA motifs. However, it is unclear how the resultant TF-nucleosome complexes are decoded by co-factors. In humans, the TF p53 regulates cell-cycle progression, apoptosis, and the DNA damage response, with a large fraction of p53-bound sites residing in nucleosome-harboring inaccessible chromatin. We examined the interaction of chromatin-bound p53 with co-factors belonging to the ubiquitin proteasome system (UPS). At two distinct motif locations on the nucleosome (super-helical location [SHL]−5.7 and SHL+5.9), the E3 ubiquitin ligase E6-E6AP was unable to bind nucleosome-engaged p53. The deubiquitinase USP7, on the other hand, readily engages nucleosome-bound p53 in vitro and in cells. A corresponding cryo-electron microscopy (cryo-EM) structure shows USP7 engaged with p53 and nucleosomes. Our work illustrates how chromatin imposes a co-factor-selective barrier for p53 interactors, whereby flexibly tethered interaction domains of co-factors and TFs govern compatibility between co-factors, TFs, and chromatin.en© 2025 The Authors. Published by Elsevier Inc. 2919 This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).transcription; transcription co-factors; genome regulationChromatinNucleosomesHumansCryoelectron MicroscopyBinding SitesProtein BindingModels, MolecularTumor Suppressor Protein p53Ubiquitin-Specific Peptidase 7Journal article10.1016/j.molcel.2025.06.027746624Isbel, L. [0000-0002-5270-4347]