Delineation of critical amino acids in activation function 1 of progesterone receptor for recruitment of transcription coregulators

Interactions governing transcriptional activity of nuclear receptors

The key players in transcriptional regulation are transcription factors (TFs), proteins that bind specific DNA sequences. Several mechanisms exist to turn TFs ‘on’ and ‘off’, including ligand binding which induces conformational changes within TFs, subsequently influencing multiple inter- and intramolecular interactions to drive transcriptional responses. Nuclear receptors are a specific family of ligand-regulated TFs whose activity relies on interactions with DNA, coregulator proteins and other receptors. These multidomain proteins also undergo interdomain interactions on multiple levels, further modulating transcriptional outputs. Cooperation between these distinct interactions is critical for appropriate transcription and remains an intense area of investigation. In this review, we report and summarize recent findings that continue to advance our mechanistic understanding of how interactions between nuclear receptors and diverse partners influence transcription.

Progestin Resistance and Corresponding Management of Abnormal Endometrial Hyperplasia and Endometrial Carcinoma

With a younger tendency in morbidity age, endometrial cancer (EC) incidence has grown year after year. Worse, even more commonly occurring is endometrial hyperplasia (EH), which is a precancerous endometrial proliferation. For young women with early EC and EH who want to preserve fertility, progestin therapy has been utilized as a routine fertility-preserving treatment approach. Nevertheless, progestin medication failure in some patients is mostly due to progestin resistance and side effects. In order to further analyze the potential mechanisms of progestin resistance in EH and EC, to provide theoretical support for effective therapeutic strategies, and to lay the groundwork for searching novel treatment approaches, this article reviews the current therapeutic effects of progestin in EH and EC, as well as the mechanisms and molecular biomarkers of progestin resistance, and systematically expounds on the potential therapeutic methods to overcome progestin resistance.

Spatial definition of the human progesterone receptor-B transcriptional complex

We report the quaternary structure of core transcriptional complex for the full-length human progesterone receptor-B (PR-B) homodimer with primary coactivator steroid receptor coactivator-2 (SRC-2) and the secondary coactivator p300/CREB-binding protein (CBP). The PR-B homodimer engages one SRC-2 mainly through its activation function 1 (AF1) in N-terminus. SRC-2 is positioned between PR-B and p300 leaving space for direct interaction between PR-B and p300 through PR-B's C-terminal AF2 and its unique AF3. Direct AF3/p300 interaction provides long-desired structural insights into the known functional differences between PR-B and the PR-A isoform lacking AF3. We reveal the contributions of each AF and demonstrate their structural basis in forming the PR-B dimer interface and PR-B/coactivator complex. Comparison of the PR-B/coactivator complex with other steroid receptor (estrogen receptor and androgen receptor) complexes also shows that each receptor has its unique mechanism for recruiting coactivators due to the highly variable N-termini among receptors.

Activation function 1 of progesterone receptor is required for progesterone antagonism of oestrogen action in the uterus

BACKGROUND

Progesterone receptor (PGR) is a master regulator of uterine function through antagonistic and synergistic interplays with oestrogen receptors. PGR action is primarily mediated by activation functions AF1 and AF2, but their physiological significance is unknown.

RESULTS

We report the first study of AF1 function in mice. The AF1 mutant mice are infertile with impaired implantation and decidualization. This is associated with a delay in the cessation of epithelial proliferation and in the initiation of stromal proliferation at preimplantation. Despite tissue selective effect on PGR target genes, AF1 mutations caused global loss of the antioestrogenic activity of progesterone in both pregnant and ovariectomized models. Importantly, the study provides evidence that PGR can exert an antioestrogenic effect by genomic inhibition of Esr1 and Greb1 expression. ChIP-Seq data mining reveals intermingled PGR and ESR1 binding on Esr1 and Greb1 gene enhancers. Chromatin conformation analysis shows reduced interactions in these genes' loci in the mutant, coinciding with their upregulations.

CONCLUSION

AF1 mediates genomic inhibition of ESR1 action globally whilst it also has tissue-selective effect on PGR target genes.

Activation function 1 of progesterone receptor is required for mammary development and regulation of RANKL during pregnancy

Progesterone receptor (PGR) is a member of the nuclear receptor superfamily of transcription factors. It is critical for mammary stem cells expansion, mammary ductal branching and alveologenesis. The transcriptional activity of PGR is mainly mediated by activation functions AF1 and AF2. Although the discovery of AF1 and AF2 propelled the understanding of the mechanism of gene regulation by nuclear receptors, their physiological roles are still poorly understood. This is largely due to the lack of suitable genetic models. The present study reports gain or loss of AF1 function mutant mouse models in the study of mammary development. The gain of function mutant AF1_QQQ exhibits hyperactivity while the loss of function mutant AF1_FFF shows hypoactivity on mammary development. However, the involvement of AF1 is context dependent. Whereas the AF1_FFF mutation causes significant impairment in mammary development during pregnancy or in response to estrogen and progesterone, it has no effect on mammary development in nulliparous mice. Furthermore, Rankl, but not Wnt4 and Areg is a major target gene of AF1. In conclusion, PGR AF1 is a pivotal ligand-dependent activation domain critical for mammary development during pregnancy and it exerts gene specific effect on PGR regulated genes.

How Protein Methylation Regulates Steroid Receptor Function

Steroid receptors (SRs) are members of the nuclear hormonal receptor family, many of which are transcription factors regulated by ligand binding. SRs regulate various human physiological functions essential for maintenance of vital biological pathways, including development, reproduction, and metabolic homeostasis. In addition, aberrant expression of SRs or dysregulation of their signaling has been observed in a wide variety of pathologies. SR activity is tightly and finely controlled by post-translational modifications (PTMs) targeting the receptors and/or their coregulators. Whereas major attention has been focused on phosphorylation, growing evidence shows that methylation is also an important regulator of SRs. Interestingly, the protein methyltransferases depositing methyl marks are involved in many functions, from development to adult life. They have also been associated with pathologies such as inflammation, as well as cardiovascular and neuronal disorders, and cancer. This article provides an overview of SR methylation/demethylation events, along with their functional effects and biological consequences. An in-depth understanding of the landscape of these methylation events could provide new information on SR regulation in physiology, as well as promising perspectives for the development of new therapeutic strategies, illustrated by the specific inhibitors of protein methyltransferases that are currently available.

90 YEARS OF PROGESTERONE: Molecular mechanisms of progesterone receptor action on the breast cancer genome

Gene regulation by steroid hormones has been at the forefront in elucidating the intricacies of transcriptional regulation in eukaryotes ever since the discovery by Karlson and Clever that the insect steroid hormone ecdysone induces chromatin puffs in giant chromosomes. After the successful cloning of the hormone receptors toward the end of the past century, detailed mechanistic insight emerged in some model systems, in particular the MMTV provirus. With the arrival of next generation DNA sequencing and the omics techniques, we have gained even further insight into the global cellular response to steroid hormones that in the past decades also extended to the function of the 3D genome topology. More recently, advances in high resolution microcopy, single cell genomics and the new vision of liquid-liquid phase transitions in the context of nuclear space bring us closer than ever to unravelling the logic of gene regulation and its complex integration of global cellular signaling networks. Using the function of progesterone and its cellular receptor in breast cancer cells, we will briefly summarize the history and describe the present extent of our knowledge on how regulatory proteins deal with the chromatin structure to gain access to DNA sequences and interpret the genomic instructions that enable cells to respond selectively to external signals by reshaping their gene regulatory networks.