
==== Front
bioRxiv
BIORXIV
bioRxiv
2692-8205
Cold Spring Harbor Laboratory

10.1101/2024.09.06.611729
preprint
2
Article
Structural proteomics defines a sequential priming mechanism for the progesterone receptor
Mann Matthew D. http://orcid.org/0000-0002-4474-4592

Wang Min
Ferreon Josephine C.
Suess Michael P.
Jain Antrix
Malovannaya Anna http://orcid.org/0000-0003-2953-6485

Pascal Bruce D. http://orcid.org/0000-0002-0301-5107

Kumar Raj
Edwards Dean P.
Griffin Patrick R. http://orcid.org/0000-0002-3404-690X

08 9 2024
2024.09.06.611729https://creativecommons.org/licenses/by-nc-nd/4.0/ This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License, which allows reusers to copy and distribute the material in any medium or format in unadapted form only, for noncommercial purposes only, and only so long as attribution is given to the creator.
http://biorxiv.org/lookup/doi/10.1101/2024.09.06.611729
nihpp-2024.09.06.611729.pdf
Abstract

The progesterone receptor (PR) is a steroid-responsive nuclear receptor, expressed as two isoforms: PR-A and PR-B. The isoforms display distinct expression patterns and biological actions in reproductive target tissues and disruption of PR-A:PR-B signaling is associated with breast cancer development potentially by altering interactions with oncogenic co-regulatory protein (CoRs). However, the molecular details of isoform-specific PR-CoR interactions that influence progesterone signaling remain poorly understood. We employed structural mass spectrometry in this study to investigate the sequential binding mechanism of purified full-length PR and full-length CoRs, steroid receptor coactivator 3 (SRC3) and p300, as complexes with target DNA. Our findings reveal selective CoR NR-box binding by PR and novel interaction surfaces between PR, SRC3, and p300, which change during complex assembly. This provides a structural model for a sequential priming mechanism that activates PR. Comparisons of PR bound to progesterone agonist versus antagonist challenges the classical model of nuclear receptor activation and repression. Collectively, we offer a peptide-level perspective on the organization of the PR transcriptional complex and elucidate the mechanisms behind the interactions of these proteins, both in active and inactive conformations.
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pmc
