The differential capacity of glucocorticoids and progestins to alter chromatin structure and induce gene expression in human breast cancer cells

Steroid receptors assemble at DNA response elements as dimers, resulting in coactivator recruitment and transcriptional activation. Our work has focused on dissecting the energetics associated with these events and quantitatively correlating the results with function. A recent finding is that different receptors dimerize with large differences in energetics. For example, estrogen receptor-α (ER-α) dimerizes with a ΔG = −12.0 kcal/mol under conditions in which the glucocorticoid receptor (GR) dimerizes with a ΔG ≤ −5.1 kcal/mol. To determine the molecular forces responsible for such differences, we created a GR/ER chimera, replacing the hormone-binding domain (HBD) of GR with that of ER-α. Cellular and biophysical analyses demonstrate that the chimera is functionally active. However, GR/ER dimerization energetics are intermediate between the parent proteins and coupled to a strong ionic linkage. Since the ER-α HBD is the primary contributor to dimerization, we suggest that GR residues constrain an ion-regulated HBD assembly reaction.

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“…Luciferase assays were performed as described previously [17]. The protein concentration of each extract was determined by BCA assay (Pierce).…”

Section: Methodsmentioning

confidence: 99%

Analysis of a glucocorticoid–estrogen receptor chimera reveals that dimerization energetics are under ionic control

Connaghan

Miura

Maluf

et al. 2013

Biophysical Chemistry

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“…Given that the promoter must be remodelled for transcriptional activation 7,10 and that the SWI-SNF/hBRG1 complex is needed for GR trans-activation 11-13 , we tested for interaction between the GR and the hBRG1 complex. Coimmunoprecipitation experiments showed that glucocorticoids promote a hormone-dependent association of the GR with the hBRG1 complex (Fig.…”

Section: The Assembly Of Transcriptional Regulatory Dna Sequences Intmentioning

confidence: 99%

Chromatin remodelling by the glucocorticoid receptor requires the BRG1 complex

Fryer

Archer

1998

Nature

452

382

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The assembly of transcriptional regulatory DNA sequences into chromatin plays a fundamental role in modulating gene expression. The promoter of the mouse mammary-tumour virus (MMTV) is packaged into a regular array of nucleosomes when it becomes stably integrated into mammalian chromosomes, and has been used to investigate the relationship between chromatin architecture and transcriptional activation by the hormone-bound glucocorticoid and progesterone receptors. In mammalian cells that express both of these receptors, the progesterone receptor activates transcription from transiently transfected MMTV DNA but not from organized chromatin templates. Moreover, the activated progesterone receptor inhibits the chromatin remodelling and consequent transcriptional stimulation that is mediated by the glucocorticoid receptor. Here we investigate the mechanism of this inhibition by characterizing the interaction of the glucocorticoid receptor with transcriptional co-activator and chromatin remodelling protein complexes. We show that when this receptor is prevented from interacting with the hBRG1/BAF chromatin remodelling complex, it can activate transcription from transiently transfected DNA but not from organized chromatin templates. Our results indicate that it may be possible to separate the transcriptional activation and chromatin remodelling activities of proteins that interact with hormone receptors.

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“…During this process, the ability of GR versus PR to activate transcription is highly cell-type specific and may depend on both the relative order of a given promoter and the remodeling capability (both histone modification and ATPase driven) the receptor is able to recruit [93, 98, 99, 101]. All SRs require SWI/SNF when promoter remodeling is needed, and each has been shown to physically interact with the SWI/SNF complex [104, 112].…”

Section: Discussionmentioning

confidence: 99%

“…The observation that in T47D/A1-2 breast cancer cells expressing both GR and PR, GR activation leads to transcriptional upregulation from both stable and transiently transfected templates while PR activation leads only to increased transcription from transiently traransfected templates reveals a major difference between GR and PR activity [79, 101]. Nuclease hypersensitivity analyses of the promoter following hormone induction shows reduced remodeling correlates with impaired function in the case of PR signaling [99, 101]. Despite weak remodeling capability, PR is capable of inhibiting GR activation when both hormones and receptors are present [101].…”

Section: Steroid Hormone Signaling and Chromatin Structurementioning

confidence: 99%

“…Nuclease hypersensitivity analyses of the promoter following hormone induction shows reduced remodeling correlates with impaired function in the case of PR signaling [99, 101]. Despite weak remodeling capability, PR is capable of inhibiting GR activation when both hormones and receptors are present [101]. Additionally, PR is able to remodel chromatin following stable introduction into a mouse GR+PR− cell line, highlighting the complexity and cell type specificity of PR activation and suggesting a system for selective receptor activation in cells such as T47D that endogenously express both receptors [98].…”

Section: Steroid Hormone Signaling and Chromatin Structurementioning

confidence: 99%

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Chromatin remodeling during glucocorticoid receptor regulated transactivation

King

Trotter

Archer

2012

Biochimica et Biophysica Acta (BBA) - Gene Regulatory Mechanism

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Steroid hormone receptor (SR) signaling leads to widespread changes in gene expression, and aberrant SR signaling can lead to malignancies including breast, prostate, and lung cancers. Chromatin remodeling is an essential component of SR signaling, and defining the process of chromatin and nucleosome remodeling during signaling is critical to the continued development of related therapies. The glucocorticoid receptor (GR) is a key SR that activates numerous promoters including the well defined MMTV promoter. The activation of MMTV by GR provides an excellent model for teasing apart the sequence of events between hormone treatment and changes in gene expression. Comparing hormone-induced transcription from stably integrated promoters with defined nucleosomal structure to that from transiently expressed, unstructured promoters permits key distinctions between interactions that require remodeling and those that do not. The importance of co-activators and histone modifications prior to remodeling and the formation of the preinitation complex that follows can also be clarified by defining key transition points in the propagation of hormonal signals. Combined with detailed mapping of proteins along the promoter, a temporal and spatial understanding of the signaling and remodeling processes begins to emerge. In this review, we examine SR signaling with a focus on GR activation of the MMTV promoter. We also discuss the ATP-dependent remodeling complex SWI/SNF, which provides the necessary remodeling activity during GR signaling and interacts with several SRs. BRG1, the central ATPase of SWI/SNF, also interacts with a set of BAF proteins that help determine the specialized function and fine-tuned regulation of BRG1 remodeling activity. BRG1 regulation comes from its own subdomains as well as its interactive partners. In particular, the HSA domain region of BRG1 and unique features of its ATPase homology appear to play key roles in regulating remodeling function. Details of the interworkings of this chromatin remodeling protein continue to be revealed and promise to improve our understanding of the role of chromatin remodeling during steroid hormone signaling.

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The differential capacity of glucocorticoids and progestins to alter chromatin structure and induce gene expression in human breast cancer cells

Cited by 18 publications

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Analysis of a glucocorticoid–estrogen receptor chimera reveals that dimerization energetics are under ionic control

Analysis of a glucocorticoid–estrogen receptor chimera reveals that dimerization energetics are under ionic control

Chromatin remodelling by the glucocorticoid receptor requires the BRG1 complex

Chromatin remodeling during glucocorticoid receptor regulated transactivation

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