Effect of estradiol on histone acetylation dynamics in human breast cancer cells

Epigenetics, cryptorchidism, and infertility

BACKGROUND

Cryptorchid boys with defective mini-puberty and impaired differentiation of Ad spermatogonia (high infertility risk) have altered expression of several genes encoding histone methyltransferases compared to patients with intact differentiation of gonocytes into Ad spermatogonia (low infertility risk).

RESULTS

High infertility risk cryptorchid boys display hypogonadotropic hypogonadism, which, together with the diminished expression of histone deacetylases and increased expression of HDAC8 decrotonylase, indicates altered histone marks and, thus, a perturbed histone code. Curative GnRHa treatment induces normalization of histone methyltransferase, chromatin remodeling, and histone deacetylase gene expression. As a result, histone changes induce differentiation of Ad spermatogonia from their precursors and, thus, fertility. In this short report, we describe key functions of histone lysine methyltransferases, chromatin remodeling proteins, and long-noncoding RNAs, and discuss their potential roles in processes leading to infertility.

CONCLUSION

Our findings suggest that epigenetic mechanisms are critical to better understanding the root causes underlying male infertility related to cryptorchidism and its possible transgenerational transmission.

Sex Differences in Psychostimulant Abuse: Implications for Estrogen Receptors and Histone Deacetylases

Substance abuse is a chronic pathological disorder that negatively affects many health and neurological processes. A growing body of literature has revealed gender differences in substance use. Compared to men, women display distinct drug-use phenotypes accompanied by recovery and rehabilitation disparities. These observations have led to the notion that sex-dependent susceptibilities exist along the progression to addiction. Within this scope, neuroadaptations following psychostimulant exposure are thought to be distinct for each sex. This review summarizes clinical findings and animal research reporting sex differences in the subjective and behavioral responses to cocaine, methamphetamine, and nicotine. This discussion is followed by an examination of epigenetic and molecular alterations implicated in the addiction process. Special consideration is given to histone deacetylases and estrogen receptor-mediated gene expression.

Estrogen, estrogen-like molecules and autoimmune diseases

In western countries, the slope of autoimmune disease (AD) incidence is increasing and affects 5-8% of the population. Mainly prevalent in women, these pathologies are due to thymic tolerance processes breakdown. The female sex hormone, estrogen, is involved in this AD female susceptibility. However, predisposition factors have to act in concert with unknown triggering environmental factors (virus, microbiota, pollution) to initiate AD. Individuals are exposed to various environmental compounds that display endocrine disruption abilities. The cellular effects of some of these molecules may be mediated through the aryl hydrocarbon receptor (AhR). Here, we review the effects of these molecules on the homeostasis of the thymic cells, the immune tolerance intrinsic factors (transcription factors, epigenetic marks) and on the immune tolerance extrinsic factors (microbiota, virus sensibility). This review highlights the contribution of estrogen and endocrine disruptors on the dysregulation of mechanisms sustaining AD development.

Genetic and epigenetic sex-specific adaptations to endurance exercise

In recent years, the interest in personalised interventions such as medicine, nutrition, and exercise is rapidly rising to maximize health outcomes and ensure the most appropriate treatments. Exercising regularly is recommended for both healthy and diseased populations to improve health. However, there are sex-specific adaptations to exercise that often are not taken into consideration. While endurance exercise training alters the human skeletal muscle epigenome and subsequent gene expression, it is still unknown whether it does so differently in men and women, potentially leading to sex-specific physiological adaptations. Elucidating sex differences in genetics, epigenetics, gene regulation and expression in response to exercise will have great health implications, as it may enable gene targets in future clinical interventions and may better individualised interventions. This review will cover this topic and highlight the recent findings of sex-specific genetic, epigenetic, and gene expression studies, address the gaps in the field, and offer recommendations for future research.

ESR2 Is Essential for Gonadotropin-Induced Kiss1 Expression in Granulosa Cells

Hypothalamic expression of Kiss1 plays an essential role in the onset of puberty, gonadal development, and ovulation. Estrogens regulate the expression of Kiss1 in the hypothalamus through estrogen receptor-α. Kiss1 is also expressed in the ovary, where its expression correlates with the onset of puberty and progression of the estrous cycle. To date, estrogen regulation of Kiss1 expression in the ovary has not been investigated. We recently observed that gonadotropin-induced Kiss1 expression was absent in Esr2-null rat ovaries even though Esr1 was present. Wild-type granulosa cells abundantly expressed Kiss1 and oocytes expressed the Kiss1 receptor. We characterized estrogen receptor-β (ESR2) regulation of Kiss1 expression in granulosa cells by identifying granulosa cell-specific transcript variants and potential regulatory regions. The Kiss1 promoter, an upstream enhancer, and a downstream enhancer all possessed conserved estrogen response elements (EREs) and showed active histone marks in gonadotropin-stimulated granulosa cells. The transcriptionally active Kiss1 promoter, as well as the enhancers, also revealed enrichment for ESR2 binding. Furthermore, activity of a Kiss1 promoter construct was induced after overexpression of ESR2 and was blocked upon mutation of an ERE within the promoter. Finally, pregnant mare serum gonadotropin and human chorionic gonadotropin administration induced phosphorylation of ESR2 and upregulated the AP-1 proteins FOSL2 and JUNB in granulosa cells. Activated MAPK ERK2 was associated with the ESR2 phosphorylation in granulosa cells, and AP-1 factors could synergistically activate the Kiss1 promoter activity. These gonadotropin-induced changes paralleled Kiss1 expression in granulosa cells. We conclude that gonadotropin-stimulated Kiss1 expression in granulosa cells is dependent on both the activation of ESR2 and the upregulation of AP-1.

Small leucine zipper protein functions as a negative regulator of estrogen receptor α in breast cancer

The nuclear transcription factor estrogen receptor α (ERα) plays a critical role in breast cancer progression. ERα acts as an important growth stimulatory protein in breast cancer and the expression level of ERα is tightly related to the prognosis and treatment of patients. Small leucine zipper protein (sLZIP) functions as a transcriptional cofactor by binding to various nuclear receptors, including glucocorticoid receptor, androgen receptor, and peroxisome proliferator-activated receptor γ. However, the role of sLZIP in the regulation of ERα and its involvement in breast cancer progression is unknown. We found that sLZIP binds to ERα and represses the transcriptional activity of ERα in ERα-positive breast cancer cells. sLZIP also suppressed the expression of ERα target genes. sLZIP disrupted the binding of ERα to the estrogen response element of the target gene promoter, resulting in suppression of cell proliferation. sLZIP is a novel co-repressor of ERα, and plays a negative role in ERα-mediated cell proliferation in breast cancer.

H4K12ac is regulated by estrogen receptor-alpha and is associated with BRD4 function and inducible transcription

Hormone-dependent gene expression requires dynamic and coordinated epigenetic changes. Estrogen receptor-positive (ER⁺) breast cancer is particularly dependent upon extensive chromatin remodeling and changes in histone modifications for the induction of hormone-responsive gene expression. Our previous studies established an important role of bromodomain-containing protein-4 (BRD4) in promoting estrogen-regulated transcription and proliferation of ER⁺ breast cancer cells. Here, we investigated the association between genome-wide occupancy of histone H4 acetylation at lysine 12 (H4K12ac) and BRD4 in the context of estrogen-induced transcription. Similar to BRD4, we observed that H4K12ac occupancy increases near the transcription start sites (TSS) of estrogen-induced genes as well as at distal ERα binding sites in an estrogen-dependent manner. Interestingly, H4K12ac occupancy highly correlates with BRD4 binding and enhancer RNA production on ERα-positive enhancers. Consistent with an importance in estrogen-induced gene transcription, H4K12ac occupancy globally increased in ER-positive cells relative to ER-negative cells and these levels were further increased by estrogen treatment in an ERα-dependent manner. Together, these findings reveal a strong correlation between H4K12ac and BRD4 occupancy with estrogen-dependent gene transcription and further suggest that modulators of H4K12ac and BRD4 may serve as new therapeutic targets for hormone-dependent cancers.

Molecular and Epigenetic Mechanism Regulating Hypothalamic Kiss1 Gene Expression in Mammals

After the discovery of hypothalamic kisspeptin encoded by the Kiss1 gene, the central mechanism regulating gonadotropin-releasing hormone (GnRH) secretion, and hence gonadotropin secretion, is gradually being unraveled. This has increased our understanding of the central mechanism regulating puberty and subsequent reproductive performance in mammals. Recently, emerging evidence has indicated the molecular and epigenetic mechanism regulating hypothalamic Kiss1 gene expression. Here we compile data regarding DNA and histone modifications in the Kiss1 promoter region and provide a hypothetic scheme of the molecular and epigenetic mechanism regulating Kiss1 gene expression in two populations of hypothalamic kisspeptin neurons, which govern puberty and subsequent reproductive performance via GnRH/gonadotropin secretion.

Spatiotemporal regulation of Heterochromatin Protein 1-alpha oligomerization and dynamics in live cells

Heterochromatin protein 1 (HP1) is a central factor in establishing and maintaining the heterochromatin state. As consequence of playing a structural role in heterochromatin, HP1 proteins can have both an activating as well as repressive function in gene expression. Here we probe how oligomerisation of the HP1-α isoform modulates interaction with chromatin, by spatially resolved fluorescence correlation spectroscopy (FCS). We find from fluctuation analysis of HP1-α dynamics that this isoform exists as a dimer around the periphery of heterochromatin foci and these foci locally rotate with characteristic turn rates that range from 5–100ms. From inhibition of HP1-α homo-oligomerization we find the slow turn rates (20–100 ms) are dimer dependent. From treatment with drugs that disrupt or promote chromatin compaction, we find that HP1-α dimers spatially redistribute to favor fast (5–10 ms) or slow (20–100 ms) turn rates. Collectively our results demonstrate HP1-α oligomerization is critical to the maintenance of heterochromatin and the tunable dynamics of this HP1 isoform.

Differentiation of developing olfactory neurons analysed in terms of coupled epigenetic landscapes

The olfactory system integrates signals from receptors expressed in olfactory sensory neurons. Each sensory neuron expresses only one of many similar olfactory receptors (ORs). The choice of receptor is made stochastically early in the differentiation process and is maintained throughout the life of the neuron. The underlying mechanism of this stochastic commitment to one of multiple similar OR genes remains elusive. We present a theoretical analysis of a mechanism that invokes important epigenetic properties of the system. The proposed model combines nucleosomes and associated read-write enzymes as mediators of a cis-acting positive feedback with a trans-acting negative feedback, thereby coupling the local epigenetic landscape of the individual OR genes in a way that allow one and only one gene to be active at any time. The model pinpoint that singular gene selection does not require transient mechanisms, enhancer elements or transcription factors to separate choice from maintenance. In addition, our hypothesis allow us to combine all reported characteristics of singular OR gene selection, in particular that OR genes are silenced from OR transgenes. Intriguingly, it predicts that OR transgenes placed in close proximity should always be expressed simultaneously, though rarely.

Blood chromatin as a biosensor of the epigenetic milieu: a tool for studies in living psychiatric patients

This article constructs an argument for using blood chromatin (contained in nucleated blood cells) as a protein biosensor to integrate the ambient epigenetic influences in the internal milieu. An analogy is made to blood glycated hemoglobin (HbA1c) in diabetes as an integrated proxy for glucose levels and body-wide protein glycation. Genome-wide chromatin can serve as an organizing principle that bridges the central and peripheral compartments by entraining commensurable gene networks. Chromatin deposition along these networks will be imposed by the totality of epigenetic influences, which incorporates significant contributions from biochemicals that readily traverse the blood-brain barrier. In a clinical trial, these influences would be dominated by pharmaceuticals designed to override pathophysiological signals. In practice, mRNA readouts would be limited to nonsynaptic gene networks whose critical nodes are occupied by a site-specific chromatin modification. Finally, chromatin measurements in peripheral tissue will retain the influences of a patient's lifestyle and unique genomic background.

Selective association of peroxiredoxin 1 with genomic DNA and COX-2 upstream promoter elements in estrogen receptor negative breast cancer cells

In a search for proteins differentially cross-linked to DNA by cisplatin or formaldehyde in normal breast epithelial and breast cancer cell lines, we identified peroxiredoxin 1 (PRDX1) as a protein preferentially cross-linked to DNA in estrogen receptor negative (ER-) MDA-MB-231 but not in estrogen receptor positive (ER+) MCF7 breast cancer cells. Indirect immunofluorescence microscopic analyses showed that PRDX1 was located in the cytoplasm and nucleus of normal and breast cancer cells, with nuclear PRDX1 associated with promyelocytic leukemia protein bodies. We demonstrated that PRDX1 association with the transcription factor nuclear factor-kappaB (NF-kappaB) in MDA-MB-231 but not in MCF7 cells contributed to PRDX1-selective recruitment to MDA-MB-231 genomic DNA. Furthermore, PRDX1 was associated with the cyclooxygenase (COX)-2 upstream promoter region at sites occupied by NF-kappaB in ER- but not in ER+ breast cancer cells. PRDX1 knockdown attenuated COX-2 expression by reducing NF-kappaB occupancy at its upstream promoter element in MDA-MB-231 but not in MCF7 cells. A phosphorylated form of PRDX1 was only present in ER- breast cancer cells. Because PRDX1 phosphorylation is known to inhibit its peroxidase activity and to promote PRDX1 oligomerization, we propose that PRDX1 acts as a chaperone to enhance the transactivation potential of NF-kappaB in ER- breast cancer cells.

ATP-citrate lyase links cellular metabolism to histone acetylation

Histone acetylation in single-cell eukaryotes relies on acetyl coenzyme A (acetyl-CoA) synthetase enzymes that use acetate to produce acetyl-CoA. Metazoans, however, use glucose as their main carbon source and have exposure only to low concentrations of extracellular acetate. We have shown that histone acetylation in mammalian cells is dependent on adenosine triphosphate (ATP)-citrate lyase (ACL), the enzyme that converts glucose-derived citrate into acetyl-CoA. We found that ACL is required for increases in histone acetylation in response to growth factor stimulation and during differentiation, and that glucose availability can affect histone acetylation in an ACL-dependent manner. Together, these findings suggest that ACL activity is required to link growth factor-induced increases in nutrient metabolism to the regulation of histone acetylation and gene expression.

ATP-Citrate Lyase Links Cellular Metabolism to Histone Acetylation

Modification of chromatin structure is usually thought of as a global, relatively nonspecific way of modulating gene expression. However, Wellen et al. (p. 1076 ; see the Perspective by Rathmell and Newgard ) demonstrate that such regulation helps link growth factor–stimulated increases in metabolism to appropriate changes in gene expression. Adenosine triphosphate (ATP)–citrate lyase (ACL), which converts citrate to acetyl–coenzyme A (CoA) in the mitochondria of mammalian cells during metabolism of glucose, was also found to be present in the nucleus, where it might regulate activity of histone acetyl transferases (HATs) by controlling the availability of acetyl-CoA. Indeed, depletion of ACL from cultured human colon carcinoma cells specifically decreased histone acetylation in the nucleus, but appeared not to affect the overall amount of acetylation of proteins in the cells. Loss of ACL in cultured mouse 3T3-L1 cells diminished the increase in histone acetylation normally associated with hormone-stimulated differentiation of these cells and inhibited the increase in expression of specific genes, such as that encoding the Glut4 glucose transporter. Thus, ACL may help cells link metabolic activity to changes in gene expression.

ATP-Citrate Lyase Links Cellular Metabolism to Histone Acetylation

Modification of chromatin structure is usually thought of as a global, relatively nonspecific way of modulating gene expression. However, Wellen et al. (p. 1076 ; see the Perspective by Rathmell and Newgard ) demonstrate that such regulation helps link growth factor–stimulated increases in metabolism to appropriate changes in gene expression. Adenosine triphosphate (ATP)–citrate lyase (ACL), which converts citrate to acetyl–coenzyme A (CoA) in the mitochondria of mammalian cells during metabolism of glucose, was also found to be present in the nucleus, where it might regulate activity of histone acetyl transferases (HATs) by controlling the availability of acetyl-CoA. Indeed, depletion of ACL from cultured human colon carcinoma cells specifically decreased histone acetylation in the nucleus, but appeared not to affect the overall amount of acetylation of proteins in the cells. Loss of ACL in cultured mouse 3T3-L1 cells diminished the increase in histone acetylation normally associated with hormone-stimulated differentiation of these cells and inhibited the increase in expression of specific genes, such as that encoding the Glut4 glucose transporter. Thus, ACL may help cells link metabolic activity to changes in gene expression.

ATP-Citrate Lyase Links Cellular Metabolism to Histone Acetylation

Modification of chromatin structure is usually thought of as a global, relatively nonspecific way of modulating gene expression. However, Wellen et al. (p. 1076 ; see the Perspective by Rathmell and Newgard ) demonstrate that such regulation helps link growth factor–stimulated increases in metabolism to appropriate changes in gene expression. Adenosine triphosphate (ATP)–citrate lyase (ACL), which converts citrate to acetyl–coenzyme A (CoA) in the mitochondria of mammalian cells during metabolism of glucose, was also found to be present in the nucleus, where it might regulate activity of histone acetyl transferases (HATs) by controlling the availability of acetyl-CoA. Indeed, depletion of ACL from cultured human colon carcinoma cells specifically decreased histone acetylation in the nucleus, but appeared not to affect the overall amount of acetylation of proteins in the cells. Loss of ACL in cultured mouse 3T3-L1 cells diminished the increase in histone acetylation normally associated with hormone-stimulated differentiation of these cells and inhibited the increase in expression of specific genes, such as that encoding the Glut4 glucose transporter. Thus, ACL may help cells link metabolic activity to changes in gene expression.

ATP-Citrate Lyase Links Cellular Metabolism to Histone Acetylation

Modification of chromatin structure is usually thought of as a global, relatively nonspecific way of modulating gene expression. However, Wellen et al. (p. 1076 ; see the Perspective by Rathmell and Newgard ) demonstrate that such regulation helps link growth factor–stimulated increases in metabolism to appropriate changes in gene expression. Adenosine triphosphate (ATP)–citrate lyase (ACL), which converts citrate to acetyl–coenzyme A (CoA) in the mitochondria of mammalian cells during metabolism of glucose, was also found to be present in the nucleus, where it might regulate activity of histone acetyl transferases (HATs) by controlling the availability of acetyl-CoA. Indeed, depletion of ACL from cultured human colon carcinoma cells specifically decreased histone acetylation in the nucleus, but appeared not to affect the overall amount of acetylation of proteins in the cells. Loss of ACL in cultured mouse 3T3-L1 cells diminished the increase in histone acetylation normally associated with hormone-stimulated differentiation of these cells and inhibited the increase in expression of specific genes, such as that encoding the Glut4 glucose transporter. Thus, ACL may help cells link metabolic activity to changes in gene expression.

ATP-Citrate Lyase Links Cellular Metabolism to Histone Acetylation

Modification of chromatin structure is usually thought of as a global, relatively nonspecific way of modulating gene expression. However, Wellen et al. (p. 1076 ; see the Perspective by Rathmell and Newgard ) demonstrate that such regulation helps link growth factor–stimulated increases in metabolism to appropriate changes in gene expression. Adenosine triphosphate (ATP)–citrate lyase (ACL), which converts citrate to acetyl–coenzyme A (CoA) in the mitochondria of mammalian cells during metabolism of glucose, was also found to be present in the nucleus, where it might regulate activity of histone acetyl transferases (HATs) by controlling the availability of acetyl-CoA. Indeed, depletion of ACL from cultured human colon carcinoma cells specifically decreased histone acetylation in the nucleus, but appeared not to affect the overall amount of acetylation of proteins in the cells. Loss of ACL in cultured mouse 3T3-L1 cells diminished the increase in histone acetylation normally associated with hormone-stimulated differentiation of these cells and inhibited the increase in expression of specific genes, such as that encoding the Glut4 glucose transporter. Thus, ACL may help cells link metabolic activity to changes in gene expression.

ATP-Citrate Lyase Links Cellular Metabolism to Histone Acetylation

Modification of chromatin structure is usually thought of as a global, relatively nonspecific way of modulating gene expression. However, Wellen et al. (p. 1076 ; see the Perspective by Rathmell and Newgard ) demonstrate that such regulation helps link growth factor–stimulated increases in metabolism to appropriate changes in gene expression. Adenosine triphosphate (ATP)–citrate lyase (ACL), which converts citrate to acetyl–coenzyme A (CoA) in the mitochondria of mammalian cells during metabolism of glucose, was also found to be present in the nucleus, where it might regulate activity of histone acetyl transferases (HATs) by controlling the availability of acetyl-CoA. Indeed, depletion of ACL from cultured human colon carcinoma cells specifically decreased histone acetylation in the nucleus, but appeared not to affect the overall amount of acetylation of proteins in the cells. Loss of ACL in cultured mouse 3T3-L1 cells diminished the increase in histone acetylation normally associated with hormone-stimulated differentiation of these cells and inhibited the increase in expression of specific genes, such as that encoding the Glut4 glucose transporter. Thus, ACL may help cells link metabolic activity to changes in gene expression.

ATP-Citrate Lyase Links Cellular Metabolism to Histone Acetylation

Modification of chromatin structure is usually thought of as a global, relatively nonspecific way of modulating gene expression. However, Wellen et al. (p. 1076 ; see the Perspective by Rathmell and Newgard ) demonstrate that such regulation helps link growth factor–stimulated increases in metabolism to appropriate changes in gene expression. Adenosine triphosphate (ATP)–citrate lyase (ACL), which converts citrate to acetyl–coenzyme A (CoA) in the mitochondria of mammalian cells during metabolism of glucose, was also found to be present in the nucleus, where it might regulate activity of histone acetyl transferases (HATs) by controlling the availability of acetyl-CoA. Indeed, depletion of ACL from cultured human colon carcinoma cells specifically decreased histone acetylation in the nucleus, but appeared not to affect the overall amount of acetylation of proteins in the cells. Loss of ACL in cultured mouse 3T3-L1 cells diminished the increase in histone acetylation normally associated with hormone-stimulated differentiation of these cells and inhibited the increase in expression of specific genes, such as that encoding the Glut4 glucose transporter. Thus, ACL may help cells link metabolic activity to changes in gene expression.

ATP-Citrate Lyase Links Cellular Metabolism to Histone Acetylation

Modification of chromatin structure is usually thought of as a global, relatively nonspecific way of modulating gene expression. However, Wellen et al. (p. 1076 ; see the Perspective by Rathmell and Newgard ) demonstrate that such regulation helps link growth factor–stimulated increases in metabolism to appropriate changes in gene expression. Adenosine triphosphate (ATP)–citrate lyase (ACL), which converts citrate to acetyl–coenzyme A (CoA) in the mitochondria of mammalian cells during metabolism of glucose, was also found to be present in the nucleus, where it might regulate activity of histone acetyl transferases (HATs) by controlling the availability of acetyl-CoA. Indeed, depletion of ACL from cultured human colon carcinoma cells specifically decreased histone acetylation in the nucleus, but appeared not to affect the overall amount of acetylation of proteins in the cells. Loss of ACL in cultured mouse 3T3-L1 cells diminished the increase in histone acetylation normally associated with hormone-stimulated differentiation of these cells and inhibited the increase in expression of specific genes, such as that encoding the Glut4 glucose transporter. Thus, ACL may help cells link metabolic activity to changes in gene expression.

ATP-Citrate Lyase Links Cellular Metabolism to Histone Acetylation

Modification of chromatin structure is usually thought of as a global, relatively nonspecific way of modulating gene expression. However, Wellen et al. (p. 1076 ; see the Perspective by Rathmell and Newgard ) demonstrate that such regulation helps link growth factor–stimulated increases in metabolism to appropriate changes in gene expression. Adenosine triphosphate (ATP)–citrate lyase (ACL), which converts citrate to acetyl–coenzyme A (CoA) in the mitochondria of mammalian cells during metabolism of glucose, was also found to be present in the nucleus, where it might regulate activity of histone acetyl transferases (HATs) by controlling the availability of acetyl-CoA. Indeed, depletion of ACL from cultured human colon carcinoma cells specifically decreased histone acetylation in the nucleus, but appeared not to affect the overall amount of acetylation of proteins in the cells. Loss of ACL in cultured mouse 3T3-L1 cells diminished the increase in histone acetylation normally associated with hormone-stimulated differentiation of these cells and inhibited the increase in expression of specific genes, such as that encoding the Glut4 glucose transporter. Thus, ACL may help cells link metabolic activity to changes in gene expression.

ATP-Citrate Lyase Links Cellular Metabolism to Histone Acetylation

Modification of chromatin structure is usually thought of as a global, relatively nonspecific way of modulating gene expression. However, Wellen et al. (p. 1076 ; see the Perspective by Rathmell and Newgard ) demonstrate that such regulation helps link growth factor–stimulated increases in metabolism to appropriate changes in gene expression. Adenosine triphosphate (ATP)–citrate lyase (ACL), which converts citrate to acetyl–coenzyme A (CoA) in the mitochondria of mammalian cells during metabolism of glucose, was also found to be present in the nucleus, where it might regulate activity of histone acetyl transferases (HATs) by controlling the availability of acetyl-CoA. Indeed, depletion of ACL from cultured human colon carcinoma cells specifically decreased histone acetylation in the nucleus, but appeared not to affect the overall amount of acetylation of proteins in the cells. Loss of ACL in cultured mouse 3T3-L1 cells diminished the increase in histone acetylation normally associated with hormone-stimulated differentiation of these cells and inhibited the increase in expression of specific genes, such as that encoding the Glut4 glucose transporter. Thus, ACL may help cells link metabolic activity to changes in gene expression.

ATP-Citrate Lyase Links Cellular Metabolism to Histone Acetylation

Modification of chromatin structure is usually thought of as a global, relatively nonspecific way of modulating gene expression. However, Wellen et al. (p. 1076 ; see the Perspective by Rathmell and Newgard ) demonstrate that such regulation helps link growth factor–stimulated increases in metabolism to appropriate changes in gene expression. Adenosine triphosphate (ATP)–citrate lyase (ACL), which converts citrate to acetyl–coenzyme A (CoA) in the mitochondria of mammalian cells during metabolism of glucose, was also found to be present in the nucleus, where it might regulate activity of histone acetyl transferases (HATs) by controlling the availability of acetyl-CoA. Indeed, depletion of ACL from cultured human colon carcinoma cells specifically decreased histone acetylation in the nucleus, but appeared not to affect the overall amount of acetylation of proteins in the cells. Loss of ACL in cultured mouse 3T3-L1 cells diminished the increase in histone acetylation normally associated with hormone-stimulated differentiation of these cells and inhibited the increase in expression of specific genes, such as that encoding the Glut4 glucose transporter. Thus, ACL may help cells link metabolic activity to changes in gene expression.

ATP-Citrate Lyase Links Cellular Metabolism to Histone Acetylation

Modification of chromatin structure is usually thought of as a global, relatively nonspecific way of modulating gene expression. However, Wellen et al. (p. 1076 ; see the Perspective by Rathmell and Newgard ) demonstrate that such regulation helps link growth factor–stimulated increases in metabolism to appropriate changes in gene expression. Adenosine triphosphate (ATP)–citrate lyase (ACL), which converts citrate to acetyl–coenzyme A (CoA) in the mitochondria of mammalian cells during metabolism of glucose, was also found to be present in the nucleus, where it might regulate activity of histone acetyl transferases (HATs) by controlling the availability of acetyl-CoA. Indeed, depletion of ACL from cultured human colon carcinoma cells specifically decreased histone acetylation in the nucleus, but appeared not to affect the overall amount of acetylation of proteins in the cells. Loss of ACL in cultured mouse 3T3-L1 cells diminished the increase in histone acetylation normally associated with hormone-stimulated differentiation of these cells and inhibited the increase in expression of specific genes, such as that encoding the Glut4 glucose transporter. Thus, ACL may help cells link metabolic activity to changes in gene expression.

ATP-Citrate Lyase Links Cellular Metabolism to Histone Acetylation

Modification of chromatin structure is usually thought of as a global, relatively nonspecific way of modulating gene expression. However, Wellen et al. (p. 1076 ; see the Perspective by Rathmell and Newgard ) demonstrate that such regulation helps link growth factor–stimulated increases in metabolism to appropriate changes in gene expression. Adenosine triphosphate (ATP)–citrate lyase (ACL), which converts citrate to acetyl–coenzyme A (CoA) in the mitochondria of mammalian cells during metabolism of glucose, was also found to be present in the nucleus, where it might regulate activity of histone acetyl transferases (HATs) by controlling the availability of acetyl-CoA. Indeed, depletion of ACL from cultured human colon carcinoma cells specifically decreased histone acetylation in the nucleus, but appeared not to affect the overall amount of acetylation of proteins in the cells. Loss of ACL in cultured mouse 3T3-L1 cells diminished the increase in histone acetylation normally associated with hormone-stimulated differentiation of these cells and inhibited the increase in expression of specific genes, such as that encoding the Glut4 glucose transporter. Thus, ACL may help cells link metabolic activity to changes in gene expression.

ATP-Citrate Lyase Links Cellular Metabolism to Histone Acetylation

Modification of chromatin structure is usually thought of as a global, relatively nonspecific way of modulating gene expression. However, Wellen et al. (p. 1076 ; see the Perspective by Rathmell and Newgard ) demonstrate that such regulation helps link growth factor–stimulated increases in metabolism to appropriate changes in gene expression. Adenosine triphosphate (ATP)–citrate lyase (ACL), which converts citrate to acetyl–coenzyme A (CoA) in the mitochondria of mammalian cells during metabolism of glucose, was also found to be present in the nucleus, where it might regulate activity of histone acetyl transferases (HATs) by controlling the availability of acetyl-CoA. Indeed, depletion of ACL from cultured human colon carcinoma cells specifically decreased histone acetylation in the nucleus, but appeared not to affect the overall amount of acetylation of proteins in the cells. Loss of ACL in cultured mouse 3T3-L1 cells diminished the increase in histone acetylation normally associated with hormone-stimulated differentiation of these cells and inhibited the increase in expression of specific genes, such as that encoding the Glut4 glucose transporter. Thus, ACL may help cells link metabolic activity to changes in gene expression.

ATP-Citrate Lyase Links Cellular Metabolism to Histone Acetylation

Modification of chromatin structure is usually thought of as a global, relatively nonspecific way of modulating gene expression. However, Wellen et al. (p. 1076 ; see the Perspective by Rathmell and Newgard ) demonstrate that such regulation helps link growth factor–stimulated increases in metabolism to appropriate changes in gene expression. Adenosine triphosphate (ATP)–citrate lyase (ACL), which converts citrate to acetyl–coenzyme A (CoA) in the mitochondria of mammalian cells during metabolism of glucose, was also found to be present in the nucleus, where it might regulate activity of histone acetyl transferases (HATs) by controlling the availability of acetyl-CoA. Indeed, depletion of ACL from cultured human colon carcinoma cells specifically decreased histone acetylation in the nucleus, but appeared not to affect the overall amount of acetylation of proteins in the cells. Loss of ACL in cultured mouse 3T3-L1 cells diminished the increase in histone acetylation normally associated with hormone-stimulated differentiation of these cells and inhibited the increase in expression of specific genes, such as that encoding the Glut4 glucose transporter. Thus, ACL may help cells link metabolic activity to changes in gene expression.

ATP-Citrate Lyase Links Cellular Metabolism to Histone Acetylation

Modification of chromatin structure is usually thought of as a global, relatively nonspecific way of modulating gene expression. However, Wellen et al. (p. 1076 ; see the Perspective by Rathmell and Newgard ) demonstrate that such regulation helps link growth factor–stimulated increases in metabolism to appropriate changes in gene expression. Adenosine triphosphate (ATP)–citrate lyase (ACL), which converts citrate to acetyl–coenzyme A (CoA) in the mitochondria of mammalian cells during metabolism of glucose, was also found to be present in the nucleus, where it might regulate activity of histone acetyl transferases (HATs) by controlling the availability of acetyl-CoA. Indeed, depletion of ACL from cultured human colon carcinoma cells specifically decreased histone acetylation in the nucleus, but appeared not to affect the overall amount of acetylation of proteins in the cells. Loss of ACL in cultured mouse 3T3-L1 cells diminished the increase in histone acetylation normally associated with hormone-stimulated differentiation of these cells and inhibited the increase in expression of specific genes, such as that encoding the Glut4 glucose transporter. Thus, ACL may help cells link metabolic activity to changes in gene expression.

ATP-Citrate Lyase Links Cellular Metabolism to Histone Acetylation

Modification of chromatin structure is usually thought of as a global, relatively nonspecific way of modulating gene expression. However, Wellen et al. (p. 1076 ; see the Perspective by Rathmell and Newgard ) demonstrate that such regulation helps link growth factor–stimulated increases in metabolism to appropriate changes in gene expression. Adenosine triphosphate (ATP)–citrate lyase (ACL), which converts citrate to acetyl–coenzyme A (CoA) in the mitochondria of mammalian cells during metabolism of glucose, was also found to be present in the nucleus, where it might regulate activity of histone acetyl transferases (HATs) by controlling the availability of acetyl-CoA. Indeed, depletion of ACL from cultured human colon carcinoma cells specifically decreased histone acetylation in the nucleus, but appeared not to affect the overall amount of acetylation of proteins in the cells. Loss of ACL in cultured mouse 3T3-L1 cells diminished the increase in histone acetylation normally associated with hormone-stimulated differentiation of these cells and inhibited the increase in expression of specific genes, such as that encoding the Glut4 glucose transporter. Thus, ACL may help cells link metabolic activity to changes in gene expression.

ATP-Citrate Lyase Links Cellular Metabolism to Histone Acetylation

Modification of chromatin structure is usually thought of as a global, relatively nonspecific way of modulating gene expression. However, Wellen et al. (p. 1076 ; see the Perspective by Rathmell and Newgard ) demonstrate that such regulation helps link growth factor–stimulated increases in metabolism to appropriate changes in gene expression. Adenosine triphosphate (ATP)–citrate lyase (ACL), which converts citrate to acetyl–coenzyme A (CoA) in the mitochondria of mammalian cells during metabolism of glucose, was also found to be present in the nucleus, where it might regulate activity of histone acetyl transferases (HATs) by controlling the availability of acetyl-CoA. Indeed, depletion of ACL from cultured human colon carcinoma cells specifically decreased histone acetylation in the nucleus, but appeared not to affect the overall amount of acetylation of proteins in the cells. Loss of ACL in cultured mouse 3T3-L1 cells diminished the increase in histone acetylation normally associated with hormone-stimulated differentiation of these cells and inhibited the increase in expression of specific genes, such as that encoding the Glut4 glucose transporter. Thus, ACL may help cells link metabolic activity to changes in gene expression.

ATP-Citrate Lyase Links Cellular Metabolism to Histone Acetylation

Modification of chromatin structure is usually thought of as a global, relatively nonspecific way of modulating gene expression. However, Wellen et al. (p. 1076 ; see the Perspective by Rathmell and Newgard ) demonstrate that such regulation helps link growth factor–stimulated increases in metabolism to appropriate changes in gene expression. Adenosine triphosphate (ATP)–citrate lyase (ACL), which converts citrate to acetyl–coenzyme A (CoA) in the mitochondria of mammalian cells during metabolism of glucose, was also found to be present in the nucleus, where it might regulate activity of histone acetyl transferases (HATs) by controlling the availability of acetyl-CoA. Indeed, depletion of ACL from cultured human colon carcinoma cells specifically decreased histone acetylation in the nucleus, but appeared not to affect the overall amount of acetylation of proteins in the cells. Loss of ACL in cultured mouse 3T3-L1 cells diminished the increase in histone acetylation normally associated with hormone-stimulated differentiation of these cells and inhibited the increase in expression of specific genes, such as that encoding the Glut4 glucose transporter. Thus, ACL may help cells link metabolic activity to changes in gene expression.

ATP-Citrate Lyase Links Cellular Metabolism to Histone Acetylation

Modification of chromatin structure is usually thought of as a global, relatively nonspecific way of modulating gene expression. However, Wellen et al. (p. 1076 ; see the Perspective by Rathmell and Newgard ) demonstrate that such regulation helps link growth factor–stimulated increases in metabolism to appropriate changes in gene expression. Adenosine triphosphate (ATP)–citrate lyase (ACL), which converts citrate to acetyl–coenzyme A (CoA) in the mitochondria of mammalian cells during metabolism of glucose, was also found to be present in the nucleus, where it might regulate activity of histone acetyl transferases (HATs) by controlling the availability of acetyl-CoA. Indeed, depletion of ACL from cultured human colon carcinoma cells specifically decreased histone acetylation in the nucleus, but appeared not to affect the overall amount of acetylation of proteins in the cells. Loss of ACL in cultured mouse 3T3-L1 cells diminished the increase in histone acetylation normally associated with hormone-stimulated differentiation of these cells and inhibited the increase in expression of specific genes, such as that encoding the Glut4 glucose transporter. Thus, ACL may help cells link metabolic activity to changes in gene expression.

Estrogen treatment induces MLL aberrations in human lymphoblastoid cells

Epidemiological data indicates increased risk of infant acute leukemia involving MLL gene aberrations with use of oral contraceptives. To determine whether estrogens might be implicated, we examined the effect of estradiol (E2) or 4-OH-E2 in an in vitro model of translocation susceptibility. Genomic DNA from the TK6 human lymphoblastoid cell line was screened by ligation mediated PCR and inverse PCR at a rearrangement hot spot within the MLL breakpoint cluster region to detect DNA aberrations. An increase in DNA double strand breaks was observed within this region after exposure to either E2 or 4-OH-E2. An increase in the frequency of MLL translocations was only found after exposure to E2. Induction of cleavage due to increased activation of apoptotic nucleases was excluded by pre-treatment with the pan-caspase inhibitor, zVAD.fmk. We conclude that concentrations of E2 and 4-OH-E2 that may occur during pregnancy, or during use of oral contraceptives, can cause aberrations of the MLL gene and could thus be a factor in the early events of leukemogenesis occurring in utero.

Modulation of alphaCaMKII signaling by rapid ERalpha action

The estrogen receptor (ER) subtypes, ERalpha and ERbeta, modulate numerous signaling cascades in the brain to result in a variety of cell fates including neuronal differentiation. We report here that 17beta-estradiol (E2) rapidly stimulates the autophosphorylation of alpha-Ca(2+)/calmodulin-dependent kinase II (alphaCaMKII) in immortalized NLT GnRH neurons, primary hippocampal neurons, and Cos7 cells co-transfected with ERalpha and alphaCaMKII. The E2-induced alphaCaMKII autophosphorylation is ERalpha- and Ca(2+)/calmodulin (CaM)-dependent. Interestingly, the hormone-dependent association of ERalpha with alphaCaMKII attenuates the positive effect of E2 on alphaCaMKII autophosphorylation, suggesting that ERalpha plays a complex role in modulating alphaCaMKII activity and may function to fine-tune alphaCaMKII-triggered signaling events. However, it appears as though the activating signal of E2 dominates the negative effect of ER since there is a clear, positive downstream response to E2-activated alphaCaMKII; pharmacological inhibitors and RNAi technology show that targets of ERalpha-mediated alphaCaMKII signaling include extracellular signal-regulated kinase 1/2 (ERK1/2), cAMP response element-binding protein (CREB), and microtubule associated protein 2 (MAP2). These findings suggest a novel model for the modulation of alphaCaMKII signaling by ERalpha, which provides a molecular link as to how E2 might influence brain function.

Effects of the in vivo supply of butyrate on histone acetylation of cecum in piglets

BACKGROUND

In vitro, butyrate inhibits histone deacetylase and down-regulates expression of cyclin D1. We hypothesized that an increased entry rate of butyrate into the cecal lumen would have similar effects in vivo.

METHODS

We used frozen cecal tissue and data from previous studies, one showing that lactulose supplementation caused an increased rate of cecal synthesis of butyrate and decreased cecal cell proliferation and density of clostridia and the other showing that cecal cell proliferation was increased by an exogenous cecal butyrate infusion at a comparable rate. The ratio of acetylated to total histones (AH ratio) and cyclin D1 mRNA expression were measured in cecal tissue.

RESULTS

Lactulose supplementation caused a 189% increase in the AH ratio (p = .004), which inversely correlated with cecal cell proliferation (r = -0.782; p = .008). With cecal butyrate infusion, we observed a significant decrease in histone acetylation (p = .02), which also inversely correlated with cecal cell proliferation (r = -0.797; p = .002). Cyclin D1 expression was increased 6.5-fold by lactulose feeding (p = .02) but decreased 50% with cecal butyrate infusion (p = .004).

CONCLUSIONS

The effects on histone acetylation of increased "endogenous" butyrate production produced by lactulose feeding, but not exogenous cecal infusion of butyrate, mirror those in vitro. Thus, bacterial production and exogenous infusion of butyrate have opposite effects on histone acetylation and cyclin D1 expression, suggesting that the composition of bacterial flora may play a role in butyrate's in vivo effects on the cell cycle.

Competitive inhibition of histone deacetylase activity by trichostatin A and butyrate

Histone deacetylases (HDACs) play a pivotal role in gene expression through their involvement in chromatin remodeling. The abnormal targeting or retention of HDACs to DNA regulatory regions is observed in many cancers, and hence HDAC inhibitors are being tested as promising anti-tumor agents. The results of previous kinetic studies, characterizing trichostatin A (TSA), as well as butyrate, as HDAC noncompetitive inhibitors, conflict with crystallographic and homology modeling data suggesting that TSA should act as a competitive inhibitor. Our results demonstrate that each of the HDAC inhibitors TSA and butyrate inhibits HDAC activity in a competitive fashion. Co-immunoprecipitation studies show that the inhibition of HDAC1 and HDAC2 activity by TSA does not disturb the extensive level of their association in the human breast cancer cell line MCF-7. Moreover, the inhibition of HDAC activity by TSA does not interfere with the interaction of HDAC1 and HDAC2 with Sin3A, a core component of the Sin3 complex. Thus, repressor complexes such as Sin3, appear to be stable in the presence of TSA. The association of HDAC2 with transcription factor Sp1 is also not affected by TSA.

Differential distribution of unmodified and phosphorylated histone deacetylase 2 in chromatin

Histone deacetylase 2 (HDAC2) is one of the histone-modifying enzymes that regulate gene expression by remodeling chromatin structure. Along with HDAC1, HDAC2 is found in the Sin3 and NuRD multiprotein complexes, which are recruited to promoters by DNA-binding proteins. In this study, we show that the majority of HDAC2 in human breast cancer cells is not phosphorylated. However, the minor population of HDAC2, preferentially cross-linked to DNA by cisplatin, is mono-, di-, or tri-phosphorylated. Furthermore, HDAC2 phosphorylation is required for formation of Sin3 and NuRD complexes and recruitment to promoters by transcription factors including p53, Rb, YY1, NF-kappaB, Sp1, and Sp3. Unmodified HDAC2 requires linker DNA to associate with chromatin but is not cross-linked to DNA by formaldehyde. We provide evidence that unmodified HDAC2 is associated with the coding region of transcribed genes, whereas phosphorylated HDAC2 is primarily recruited to promoters.

Chromatin organization and nuclear microenvironments in cancer cells

Nuclear morphometric descriptors such as nuclear size, shape, DNA content and chromatin organization are used by pathologists as diagnostic markers for cancer. However, our knowledge of events resulting in changes in nuclear shape and chromatin organization in cancer cells is limited. Nuclear matrix proteins, which include lamins, transcription factors (Sp1) and histone modifying enzymes (histone deacetylases), and histone modifications (histone H3 phosphorylation) have roles in organizing chromatin in the interphase nucleus, regulating gene expression programs and determining nuclear shape. Histone H3 phosphorylation, a downstream target of the Ras-mitogen activated protein kinase pathway, is involved in neoplastic transformation. This article will review genetic and epigenetic events that alter chromatin organization in cancer cells and the role of the nuclear matrix in determining nuclear morphology.

Decondensing the protamine domain for transcription

Potentiation is the transition from higher-order, transcriptionally silent chromatin to a less condensed state requisite to accommodating the molecular elements required for transcription. To examine the underlying mechanism of potentiation an approximately 13.7-kb mouse protamine domain of increased nuclease sensitivity flanked by 5' and 3' nuclear matrix attachment regions was defined. The potentiated DNase I-sensitive region is formed at the pachytene spermatocyte stage with the recruitment to the nuclear matrix of a large approximately 9.6-kb region just upstream of the domain. Attachment is then specified in the transcribing round spermatid, recapitulating the organization of the human cluster. In comparison to other modifiers that have no effect, i.e., histone methylation, HP1, and SATB1, topoisomerase engages nuclear matrix binding as minor marks of histone acetylation appear. Reorganization is marked by specific sites of topoisomerase II activity that are initially detected in leptotene-zygotene spermatocytes just preceding the formation of the DNase I-sensitive domain. This has provided a likely model of the events initiating potentiation, i.e., the opening of a chromatin domain.

Sp1 and Sp3 foci distribution throughout mitosis

The mammalian transcription factors Sp1 and Sp3 compete for the same DNA binding sites but play different roles in the regulation of expression of numerous genes. It is known that, in the interphase nucleus, Sp1 and Sp3 are organized into distinct foci. In this study, we show that throughout the mitotic process, while being displaced from the condensed chromosomes and dispersed throughout the cell, Sp1 and Sp3 maintain their separate punctate distributions. In metaphase, both Sp1 and Sp3 foci show a high degree of colocalization with microfilaments, suggesting that F-actin is involved in the organization of Sp1 and Sp3 foci during mitosis. Constant Sp1 and Sp3 levels were observed during mitosis, signifying a recovery of the pre-existing Sp1 and Sp3 population in newly formed nuclei. In late telophase, Sp1 and Sp3 are equally segregated between daughter cells, and their subnuclear organization as distinct foci is restored in a sequential fashion with Sp3 regrouping into the newly formed nuclei prior to Sp1. Both Sp1 and Sp3 return to the nuclei ahead of RNA polymerase II. Our results support a model in which entry of Sp1, Sp3 and RNA polymerase II into the newly formed nuclei is an ordered process.

Recruitment of histone deacetylase 4 to the N-terminal region of estrogen receptor alpha

Transcriptional activation of estrogen receptor alpha (ERalpha) is regulated by the ligand-dependent activation function 2 and the constitutively active N-terminal activation function 1. To identify ERalpha N-terminal-specific coregulators, we screened a breast cDNA library by T7 phage display and isolated histone deacetylase 4 (HDAC4). HDAC4 interacts with the ERalpha N terminus both in vitro and in vivo. Presence of the ERalpha DNA binding domain and hinge region reduce HDAC4 recruitment whereas full-length ERalpha enhances recruitment. HDAC4 interaction is selective for the ERalpha and not ERbeta N terminus and occurs in the nucleus. We demonstrate in vivo that HDAC4 is recruited by the N terminus to the promoter of an endogenous estrogen responsive gene. HDAC4 suppresses transcriptional activation of ERalpha by estrogen and selective ER modulators (SERMs) such as tamoxifen in a cell type-dependent manner. Consistently, silencing of HDAC4 promotes the agonist effect of SERMs (tamoxifen and raloxifene) in a cell type-specific manner. These findings indicate a role for HDAC4 in regulating ERalpha activity as a novel N-terminal coregulator and uncover a mechanism by which certain cell types regulate SERM behavior.

Differential intranuclear organization of transcription factors Sp1 and Sp3

Sp1 and Sp3 are ubiquitously expressed mammalian transcription factors that activate or repress the expression of a variety of genes and are thought to compete for the same DNA binding site. We used indirect immunofluorescence microscopy and image deconvolution to show that Sp1 and Sp3 are organized into distinct nonoverlapping domains in human breast and ovarian cells. Domains of Sp1 and Sp3 infrequently associate with sites of transcription. Sp3 partitions with the tightly bound nuclear protein fraction of hormone responsive MCF-7 breast cancer cells, whereas only a subpopulation of Sp1 is found in that fraction. Both Sp1 and Sp3 are bound to the nuclear matrix, and the nuclear matrix-associated sites of Sp1 and Sp3 are different. Indirect immunofluorescence studies demonstrate that Sp1 and Sp3 associate with histone deacetylases 1 and 2 and with the estrogen receptor alpha, albeit at low frequencies in MCF-7 cells. Chromatin immunoprecipitation (ChIP) and re-ChIP assays revealed that although both Sp1 and Sp3 bind to the estrogen-responsive trefoil factor 1 promoter in MCF-7 cells, they do not occupy the same promoter. Our results demonstrate the different features of Sp1 and Sp3, providing further evidence that Sp3 is not a functional equivalent of Sp1.

Selenium disrupts estrogen signaling by altering estrogen receptor expression and ligand binding in human breast cancer cells

Cancer prevention studies suggest that selenium is effective in reducing the incidence of cancers including prostate, colon, and lung cancers. Previous reports showed that selenium inhibits premalignant human breast MCF-10AT1 and MCF10AT3B cell growth in vitro and reduces mammary tumor incidence after exposure to carcinogens in tumor models. Because estrogen is critical to the development and differentiation of estrogen target tissues, including the breast, the present study was designed to examine the effect of selenium on estrogen receptor (ER) expression and activation using methylseleninic acid (MSA), an active form of selenium in vitro. Selenium decreased the levels of expression of ERalpha mRNA and protein and reduced the binding of labeled estradiol to estrogen receptor in MCF-7 cells. Selenium inhibited the trans-activating activity of estrogen receptor in MCF-7 cells expressing functional estrogen receptor using a luciferase reporter construct linked to estrogen responsive element. Selenium decreased the binding of estrogen receptor to the estrogen responsive element site using an electrophoretic mobility gel shift assay. Selenium suppressed estrogen induction of the endogenous target gene c-myc. In contrast to the effect on ERalpha in MCF-7 cells, selenium increased ERbeta mRNA expression in MDA-MB231 human breast cancer cells. Thus, differential regulation of ERalpha and ERbeta in breast cancer cells may represent a novel mechanism of selenium action and provide a rationale for selenium breast cancer prevention trial.

Histone acetylation in reproductive organs: Significance of histone deacetylase inhibitors in gene transcription

Acetylation of histones is cooperatively regulated by two groups of enzymes, histone acetyltransferases and histone deacetylases. Histone acetylation status plays a fundamental role in the level of gene transcription; numerous studies have demonstrated that histone deacetylase inhibitors cause cell growth arrest, apoptosis, and differentiation in various cells including human mammary gland and endometrial cells by altering transcription of a small number of genes. A recent study has also shown that a highly acetylated histone status alters cell motility. After the present review of the published reports on the mechanisms underlying histone acetylation and in vitro effects of histone deacetylase inhibitors, we conclude that this class of agents may have potential not only as anticancer drugs, but also as inducers of differentiation and/or motility for benign gynecologic conditions such as endometriosis and disorders of endometrial differentiation and dysfunction. (Reprod Med Biol 2005; 4: 115-122).

Semirandom sampling to detect differentiation-related and age-related epigenome remodeling

With completion of the human genome project, patterns of higher order chromatin structure can be easily related to other features of genome organization. A well-studied aspect of chromatin, histone H4 acetylation, is examined here on the basis of its role in setting competence for gene activation. Three applications of a new hybrid genome sampling-chromatin immunoprecipitation strategy are described. The first explores aspects of epigenome architecture in human fibroblasts. A second focuses on chromatin from HL-60 promyelocytic leukemia cells before and after differentiation into macrophage-like cells. A third application explores age-related epigenome change. In the latter, acetylation patterns are compared in human skin fibroblast chromatin from donors of various ages. Two sites are reported at which observed histone H4 acetylation differences suggest decreasing acetylation over time. The sites, located in chromosome 4p16.1 and 4q35.2 regions, appear to remodel during late fetal-early child development and from preadolescence through adult life, respectively.

Estrogen regulation of trefoil factor 1 expression by estrogen receptor alpha and Sp proteins

Estrogen-responsive genes in human breast cancer cells often have an estrogen response element (ERE) positioned next to an Sp1 binding site. In chromatin immunoprecipitation (ChIP) assays, we investigated the binding of estrogen receptor alpha (ER), Sp1, and Sp3 to the episomal and native estrogen-responsive trefoil factor 1 (TFF1; formerly pS2) promoter in MCF-7 breast cancer cells. Mutation of the Sp site upstream of the ERE reduced estrogen responsiveness and prevented binding of Sp1 and Sp3, but not ER to the episomal promoter. In the absence of estradiol (E2), Sp1, Sp3, histone deacetylase 1 (HDAC), and HDAC2, and low levels of acetylated H3 and H4 are associated with the native promoter, with the histones being engaged in dynamic reversible acetylation. Following E2 addition, levels of ER and acetylated H3 and H4 bound to the native promoter increases. There is clearance of Sp1, but not of Sp3, from the promoter while HDAC1 and HDAC2 remain bound. These data are consistent with a model in which Sp1 or Sp3 aid in recruitment of HDACs and histone acetyltransferases (HATs) to mediate dynamic acetylation of histones associated with the TFF1 promoter, which is in a state of readiness to respond to events occurring following the addition of estrogen.