Histone deacetylase 1: a target of 9-hydroxystearic acid in the inhibition of cell growth in human colon cancer

Recent studies have shown that an endogenous lipoperoxidation product, 9-hydroxystearic acid (9-HSA), acts in colon carcinoma cells (HT29) as a growth inhibitor by inducing p21(WAF1) in an immediate-early, p53-independent manner and that p21(WAF1) is required for 9-HSA-mediated growth arrest in HT29 cells. It is conceivable, therefore, to hypothesize that the cytostatic effect induced by this agent is at least partially associated with a molecular mechanism that involves histone deacetylase 1 (HDAC1) inhibition, as demonstrated for sodium butyrate and other specific inhibitors, such as trichostatin A and hydroxamic acids. Here, we show that, after administration, 9-HSA causes an accumulation of hyperacetylated histones and strongly inhibits the activity of HDAC1. The interaction of 9-HSA with the catalytic site of the enzyme has been highlighted by computational modeling of the human HDAC1, using its homolog from the hyperthermophilic Aquifex aeolicus as a template. Consistent with the experimental data, we find that 9-HSA can bind to the active site of the protein, showing that the inhibition of the enzyme can be explained at the molecular level by the ligand-protein interaction.     

Cyclin D1 inhibits peroxisome proliferator-activated receptor gamma-mediated adipogenesis through histone deacetylase recruitment

The cyclin D1 gene encodes the labile serum-inducible regulatory subunit of a holoenzyme that phosphorylates and inactivates the retinoblastoma protein. Overexpression of cyclin D1 promotes cellular proliferation and normal physiological levels of cyclin D1 function to inhibit adipocyte differentiation in vivo. We have previously shown that cyclin D1 inhibits peroxisome proliferator-activated receptor (PPAR)gamma-dependent activity through a cyclin-dependent kinase- and retinoblastoma protein-binding-independent mechanism. In this study, we determined the molecular mechanism by which cyclin D1 regulated PPARgamma function. Herein, murine embryonic fibroblast (MEF) differentiation by PPARgamma ligand was associated with a reduction in histone deacetylase (HDAC1) activity. Cyclin D1-/- MEFs showed an increased propensity to undergo differentiation into adipocytes. Genetic deletion of cyclin D1 reduced HDAC1 activity. Reconstitution of cyclin D1 into the cyclin D1-/- MEFs increased HDAC1 activity and blocked PPARgamma-mediated adipogenesis. PPARgamma activity was enhanced in cyclin D1-/- cells. Reintroduction of cyclin D1 inhibited basal and ligand-induced PPARgamma activity and enhanced HDAC repression of PPARgamma activity. Cyclin D1 bound HDAC in vivo and preferentially physically associated with HDAC1, HDAC2, HDAC3, and HDAC5. Chromatin immunoprecipitation assay demonstrated that cyclin D1 enhanced recruitment of HDAC1 and HDAC3 and histone methyltransferase SUV39H1 to the PPAR response element of the lipoprotein lipase promoter and decreased acetylation of total histone H3 and histone H3 lysine 9. Collectively, these studies suggest an important role of cyclin D1 in regulation of PPARgamma-mediated adipocyte differentiation through recruitment of HDACs to regulate PPAR response element local chromatin structure and PPARgamma function.     

Rapid induction of histone hyperacetylation and cellular differentiation in human breast tumor cell lines following degradation of histone deacetylase-1

Quinidine inhibits proliferation and promotes cellular differentiation in human breast tumor epithelial cells. Previously we showed quinidine arrested MCF-7 cells in G(1) phase of the cell cycle and led to a G(1) to G(0) transition followed by apoptotic cell death. The present experiments demonstrated that MCF-7, MCF-7ras, T47D, MDA-MB-231, and MDA-MB-435 cells transiently differentiate before undergoing apoptosis in response to quinidine. The cells accumulated lipid droplets, and the cytokeratin 18 cytoskeleton was reorganized. Hyperacetylated histone H4 appeared within 2 h of the addition of quinidine to the medium, and levels were maximal by 24 h. Quinidine-treated MCF-7 cells showed elevated p21(WAF1), hypophosphorylation and suppression of retinoblastoma protein, and down-regulation of cyclin D1, similar to the cell cycle response observed with cells induced to differentiate by histone deacetylase inhibitors, trichostatin A, and trapoxin. Quinidine did not show evidence for direct inhibition of histone deacetylase enzymatic activity in vitro. HDAC1 was undetectable in MCF-7 cells 30 min after addition of quinidine to the growth medium. The proteasome inhibitors MG-132 and lactacystin completely protected HDAC1 from the action of quinidine. We conclude that quinidine is a breast tumor cell differentiating agent that causes the loss of HDAC1 via a proteasomal sensitive mechanism.     

Species-dependent enantioselective pharmacokinetics of PNU-103017, a Pyrone HIV protease inhibitor

PNU-103017, 4-Cyano-N-(3-(cyclopropyl(5,6,7,8,9,10-hexahydro-4-hydroxy-2-oxo-2H-cycloocta(b) pyran-3-yl)methyl)phenyl)-benzenesulfonamide, is a selective HIV aspartyl protease inhibitor under evaluation as a potential oral treatment of Acquired Immunodeficiency Diseases. PNU-103017 is a racemic mixture of two enantiomers, designated PNU-103264 (R-) and PNU-103265 (S-). Stereoselective pharmacokinetics of the two enantiomers of PNU-103017 were observed in the dog, rat, and human after single and multiple dose administration of the racemate and were apparently species-dependent. Mean enantiomeric ratios of plasma concentrations (R-/S-) at each time point were greater than 1 in the dog, ranging from 1.22 to 3.06, but less than 1 in the rat and in the human, ranging from 0.44 to 0.80 and 0.23 to 0.73, respectively. A trend towards increased or decreased (farther from 1:1, R-/S-) enantiomeric ratio of plasma concentrations with time after each administration was also observed. The enantiomeric ratio remained unchanged after multiple dose administration in the rat, dog, and human although enzyme induction and increased plasma clearance were observed for both enantiomers. Chirality 10:210–216, 1998. © 1998 Wiley-Liss, Inc.     

Cyclin D1 binding to the androgen receptor (AR) NH2-terminal domain inhibits activation function 2 association and reveals dual roles for AR corepression

The androgen receptor (AR) is a member of the nuclear receptor superfamily, the activity of which is critical for the development and progression of prostate cancer. We and others have previously demonstrated that cyclin D1 is a potent corepressor of the AR. Although cyclin D1 is suspected to recruit histone deacetylases to the AR complex, previous studies have demonstrated that this activity alone is insufficient for cyclin D1 function. Here, we uncover a novel, secondary means of cyclin D1-mediated repression, through modulation of AR amino-carboxy terminal interactions. We show that cyclin D1 predominantly binds the N-terminal domain of the AR, dependent on the AR 23FxxLF27 motif. Through this motif, cyclin D1 abrogates the ability of the AR N-terminal domain to interact with the C terminus. Secondary amino-terminal domain sites capable of fostering interaction with the C terminus were refractory to cyclin D1 action, indicating that the ability of cyclin D1 to modulate AR amino-carboxy terminal interactions is specific to 23FxxLF27. Deletion of the N-terminal cyclin D1 binding site severely compromised AR activity (due to loss of FxxLF) but unmasked a repressor action through interaction with the AR C terminus. In summary, these data reveal novel, unexpected mechanisms of cyclin D1 activity and demonstrate that this function of cyclin D1 is critical for AR modulation.     

Novel Interaction of Class IIb Histone Deacetylase 6 (HDAC6) with Class IIa HDAC9 Controls Gonadotropin Releasing Hormone (GnRH) Neuronal Cell Survival and Movement

The impact of histone deacetylases (HDACs) in the control of gonadotropin releasing hormone (GnRH) neuronal development is unknown. We identified an increase in many HDACs in GT1-7 (differentiated) compared with NLT (undifferentiated) GnRH neuronal cell lines. Increased HDAC9 mRNA and protein and specific deacetylase activity in GT1-7 cells suggested a functional role. Introduction of HDAC9 in NLT cells protected from serum withdrawal induced apoptosis and impaired basal neuronal cell movement. Conversely, silencing of endogenous HDAC9 in GT1-7 cells increased apoptosis and cell movement. Comparison of WT and mutant HDAC9 constructs demonstrated that the HDAC9 pro-survival effects required combined cytoplasmic and nuclear localization, whereas the effects on cell movement required a cytoplasmic site of action. Co-immunoprecipitation demonstrated a novel interaction of HDAC9 selectively with the Class IIb HDAC6. HDAC6 was also up-regulated at the mRNA and protein levels, and HDAC6 catalytic activity was significantly increased in GT1-7 compared with NLT cells. HDAC9 interacted with HDAC6 through its second catalytic domain. Silencing of HDAC6, HDAC9, or both, in GT1-7 cells augmented apoptosis compared with controls. HDAC6 and -9 had additive effects to promote cell survival via modulating the BAX/BCL2 pathway. Silencing of HDAC6 resulted in an activation of movement of GT1-7 cells with induction in acetylation of α-tubulin. Inhibition of HDAC6 and HDAC9 together resulted in an additive effect to increase cell movement but did not alter the acetylation of αtubulin. Together, these studies identify a novel interaction of Class IIa HDAC9 with Class IIb HDAC6 to modulate cell movement and survival in GnRH neurons.     

The Suv39H1 methyltransferase inhibitor chaetocin causes induction of integrated HIV-1 without producing a T cell response

Latent HIV-1 (human immunodeficiency virus-1) provirus is unaffected by current AIDS (acquired immunodeficiency syndrome) therapies. We show here that chaetocin, an SUV39H1 histone methyltransferase inhibitor, causes 25-fold induction of latent HIV-1 expression, while producing minimal toxicity and without causing T cell activation. Induction is associated with loss of histone H3 lysine 9 (H3K9) trimethylation at the long terminal repeat (LTR) promoter, and a corresponding increase in H3K9 acetylation. The effect of chaetocin is amplified synergistically in combination with histone deacetylase (HDAC) inhibitors. These results indicate that chaetocin may provide a therapy to purge cells of latent HIV-1, possibly in combination with other chromatin remodeling drugs.     

Cloning, expression, and biochemical characterization of a new histone deacetylase-like protein from Thermus caldophilus GK24

Histone deactylases (HDACs) are members of an ancient enzyme family found in eukaryotes as well as in prokaryotes such as archaebacteria and eubacteria. We here report a new histone deacetylase (Tca HDAC) that was cloned from the genomic library of Thermus caldophilus GK24 based on homology analysis with human histone deacetylase1 (HDAC1). The gene contains an open reading frame encoding 375 amino acids with a calculated molecular mass of 42,188 Da and the deduced amino acid sequence of Tca HDAC showed a 31% homology to human HDAC1. The Tca HDAC gene was over-expressed in Escherichia coli using a Glutathione-S transferase (GST) fusion vector (pGEX-4T-1) and the purified protein showed a deacetylase activity toward the fluorogenic substrate for HDAC. Moreover, the enzyme activity was inhibited by trichostatin A, a specific HDAC inhibitor, in a dose-dependent manner. Optimum temperature and pH of the enzyme was found to be approximately 70 degrees C and 7.0, respectively. In addition, zinc ion is required for catalytic activity of the enzyme. Together, these data demonstrate that Tca HDAC is a new histone deacetylase-like enzyme from T. caldophilus GK24 and will be a useful tool for deciphering the role of HDAC in the prokaryote and development of new biochemical reactions.