Histone deacetylase 1-mediated histone modification regulates osteoblast differentiation

Osteogenesis is a complex process associated with dramatic changes in gene expression. To elucidate whether modifications in chromatin structure are involved in osteoblast differentiation, we examined the expression levels of histone deacetylases (HDACs) and the degree of histone acetylation at the promoter regions of osteogenic genes. During osteogenesis, total HDAC enzymatic activity was decreased with significant reduction in HDAC1 expression. Consistently, recruitment of HDAC1 to the promoters of osteoblast marker genes, including osterix and osteocalcin, was down-regulated, whereas histone H3 and H4 were hyperacetylated at those promoters during osteoblast differentiation. Moreover, suppression of HDAC activity with a HDAC inhibitor, sodium butyrate, accelerated osteogenesis by inducing osteoblast marker genes including osteopontin and alkaline phosphatase. Consistently, knockdown of HDAC1 by the short interference RNA system stimulated osteoblast differentiation. Taken together, these data propose that down-regulation of HDAC1 is an important process for osteogenesis.     

Histone deacetylase 6 regulates human immunodeficiency virus type 1 infection

Efficient human immunodeficiency virus (HIV)-1 infection depends on multiple interactions between the viral gp41/gp120 envelope (Env) proteins and cell surface receptors. However, cytoskeleton-associated proteins that modify membrane dynamics may also regulate the formation of the HIV-mediated fusion pore and hence viral infection. Because the effects of HDAC6-tubulin deacetylase on cortical alpha-tubulin regulate cell migration and immune synapse organization, we explored the possible role of HDAC6 in HIV-1-envelope-mediated cell fusion and infection. The binding of the gp120 protein to CD4+-permissive cells increased the level of acetylated alpha-tubulin in a CD4-dependent manner. Furthermore, overexpression of active HDAC6 inhibited the acetylation of alpha-tubulin, and remarkably, prevented HIV-1 envelope-dependent cell fusion and infection without affecting the expression and codistribution of HIV-1 receptors. In contrast, knockdown of HDAC6 expression or inhibition of its tubulin deacetylase activity strongly enhanced HIV-1 infection and syncytia formation. These results demonstrate that HDAC6 plays a significant role in regulating HIV-1 infection and Env-mediated syncytia formation.     

Histone deacetylase 6 regulates growth factor-induced actin remodeling and endocytosis

Histone deacetylase 6 (HDAC6) is a cytoplasmic deacetylase that uniquely catalyzes α-tubulin deacetylation and promotes cell motility. However, the mechanism underlying HDAC6-dependent cell migration and the role for microtubule acetylation in motility are not known. Here we show that HDAC6-induced global microtubule deacetylation was not sufficient to stimulate cell migration. Unexpectedly, in response to growth factor stimulation, HDAC6 underwent rapid translocation to actin-enriched membrane ruffles and subsequently became associated with macropinosomes, the vesicles for fluid-phase endocytosis. Supporting the importance of these associations, membrane ruffle formation, macropinocytosis, and cell migration were all impaired in HDAC6-deficient cells. Conversely, elevated HDAC6 levels promoted membrane ruffle formation with a concomitant increase in macropinocytosis and motility. In search for an HDAC6 target, we found that heat shock protein 90 (Hsp90), another prominent substrate of HDAC6, was also recruited to membrane ruffles and macropinosomes. Significantly, inhibition of Hsp90 activity suppressed membrane ruffling and cell migration, while expression of an acetylation-resistant Hsp90 mutant promoted ruffle formation. Our results uncover a surprising role for HDAC6 in actin remodeling-dependent processes and identify the actin cytoskeleton as an important target of HDAC6-regulated protein deacetylation.     

Histone deacetylase inhibition regulates miR-449a levels in skeletal muscle cells

microRNAs (miRNAs) are small non-coding RNAs that regulate cellular processes by fine-tuning the levels of their target mRNAs. However, the regulatory elements determining cellular miRNA levels are not well studied. Previously, we had described an altered miRNA signature in the skeletal muscle of db/db mice. Here, we sought to explore the role of epigenetic mechanisms in altering these miRNAs. We show that histone deacetylase (HDAC) protein levels and activity are upregulated in the skeletal muscle of diabetic mice. In C2C12 cells, HDAC inhibition using suberoylanilide hydroxamic acid (SAHA) altered the levels of 24 miRNAs: 15 were downregulated and 9 were upregulated. miR-449a, an intronic miRNA localized within the Cdc20b gene, while being downregulated in the skeletal muscle of diabetic mice, was the most highly upregulated during HDAC inhibition. The host gene, Cdc20b, was also significantly upregulated during HDAC inhibition. Bioinformatics analyses identified a common promoter for both Cdc20b and miR-449a that harbors significant histone acetylation marks, suggesting the possibility of regulation by histone acetylation-deacetylation. These observations suggest an inverse correlation between miR-449a levels and HDAC activity, in both SAHA-treated skeletal muscle cells and db/db mice skeletal muscle. Further, in SAHA-treated C2C12 cells, we observed augmented occupancy of acetylated histones on the Cdc20b/miR-449a promoter, which possibly promotes their upregulation. In vivo injection of SAHA to db/db mice significantly restored skeletal muscle miR-449a levels. Our results provide insights into the potential regulatory role of epigenetic histone acetylation of the miR-449a promoter that may regulate its expression in the diabetic skeletal muscle.     

Histone deacetylase inhibition by sodium valproate regulates polarization of macrophage subsets

Recent studies suggest that change of macrophage phenotype (M1/M2) is associated with autoimmune diseases. Sodium valproate (VPA) is a class I histone deacetylase (HDAC) inhibitor, which has immunomodulatory function in graft-versus-host disease. However, its impact on macrophage polarization has not been defined. We evaluated the effects of VPA on both mouse macrophage cell line RAW264.7 and primary mouse bone marrow macrophages (BMMs). Exposure to VPA significantly repressed the production of interleukin 12 (IL-12), and tumor necrosis factor α by lipopolysaccharide (LPS)-induced macrophage activation, in contrast, promoted IL-10 expression. VPA also affected the costimulatory molecule expression on LPS-stimulated RAW264.7 and BMMs (downregulation of CD40 and CD80, and upregulation of CD86). Specifically, VPA inhibited macrophage-mediated T helper 1 (Th1) effector but enhanced Th2 effector cell activation. Together, our preclinical study demonstrates that VPA significantly affects the phenotype and function of macrophage, indicating an important role of HDAC activity in immune regulation and inflammation. It also provides a rationale to evaluate VPA activity for the treatment of macrophage dysfunction-associated diseases.     

Histone deacetylase inhibitors suppress natural killer cell cytolytic activity

Treatment of transformed cells from leukemia or solid tumors with histone deacetylase inhibitors (HDACi) was shown to increase their sensitivity to NK cell lysis. In this study, treatment of IL-2-activated NK cells with HDACi including suberoylanilide hydroxamic acid and valproic acid was studied. Both drugs at therapeutic concentrations inhibited NK cell cytotoxicity on human leukemic cells. This inhibition was associated with decreased expression and function of NK cell activating receptors NKp46 and NKp30 as well as impaired granule exocytosis. NFkappaB activation in IL-2-activated NK cells was inhibited by both HDACi. Pharmacologic inhibition of NFkappaB activity resulted in similar effects on NK cell activity like those observed for HDACi. These results demonstrate for the first time that HDACi prevent NK cytotoxicity by downregulation of NK cell activating receptors probably through the inhibition of NFkappaB activation.     

Histone deacetylase activity is required for embryonic stem cell differentiation

Mammalian development requires commitment of cells to restricted lineages, which requires epigenetic regulation of chromatin structure. Epigenetic modifications were examined during in vitro differentiation of murine embryonic stem (ES) cells. Global histone acetylation, a euchromatin marker, declines dramatically within 1 day of differentiation induction and partially rebounds by day 2. Histone H3-Lys9 methylation, a heterochromatin marker, increases during in vitro differentiation. Conversely, the euchromatin marker H3-Lys4 methylation transiently decreases, then increases to undifferentiated levels by day 4, and decreases by day 6. Global cytosine methylation, another heterochromatin marker, increases slightly during ES cell differentiation. Chromatin structure of the Oct4 and Brachyury gene promoters is modulated in concert with their pattern of expression during ES cell differentiation. Importantly, prevention of global histone deacetylation by treatment with trichostatin A prevents ES cell differentiation. Hence, ES cells undergo functionally important global and gene-specific remodeling of chromatin structure during in vitro differentiation. genesis 38:32-38, 2004.     

Histone deacetylase activity is retained in primary neurons expressing mutant huntingtin protein

Perturbation of histone acetyl-transferase (HAT) activity is implicated in the pathology of polyglutamine diseases, and suppression of the counteracting histone deacetylase (HDAC) proteins has been proposed as a therapeutic candidate for these intractable disorders. Meanwhile, it is not known whether mutant polyglutamine disease protein affects the HDAC activity in declining neurons, though the answer is essential for application of anti-HDAC drugs for polyglutamine diseases. Here, we show the effect of mutant huntingtin (htt) protein on the expression and activity of HDAC proteins in rat primary cortical neurons as well as in human Huntington's disease (HD) brains. Our findings indicate that expression and activity of HDAC proteins are not repressed by mutant htt protein. Furthermore, expression of normal and mutant htt protein slightly increased HDAC activity although the effects of normal and mutant htt were not remarkably different. In human HD cerebral cortex, HDAC5 immunoreactivity was increased in the nucleus of striatal and cortical neurons, suggesting accelerated nuclear import of this class II HDAC. Meanwhile, western blot and immunohistochemical analyses showed no remarkable change in the expression of class I HDAC proteins such as HDAC1 and HDCA8. Collectively, retained activity in affected neurons supports application of anti-HDAC drugs to the therapy of HD.     

Histone deacetylase 1 regulates retinal neurogenesis in zebrafish by suppressing Wnt and Notch signaling pathways

In the developing vertebrate retina, progenitor cells initially proliferate but begin to produce postmitotic neurons when neuronal differentiation occurs. However, the mechanism that determines whether retinal progenitor cells continue to proliferate or exit from the cell cycle and differentiate is largely unknown. Here, we report that histone deacetylase 1 (Hdac1) is required for the switch from proliferation to differentiation in the zebrafish retina. We isolated a zebrafish mutant, ascending and descending (add), in which retinal cells fail to differentiate into neurons and glial cells but instead continue to proliferate. The cloning of the add gene revealed that it encodes Hdac1. Furthermore, the ratio of the number of differentiating cells to that of proliferating cells increases in proportion to Hdac activity, suggesting that Hdac proteins regulate a crucial step of retinal neurogenesis in zebrafish. Canonical Wnt signaling promotes the proliferation of retinal cells in zebrafish, and Notch signaling inhibits neuronal differentiation through the activation of a neurogenic inhibitor, Hairy/Enhancer-of-split (Hes). We found that both the Wnt and Notch/Hes pathways are activated in the add mutant retina. The cell-cycle progression and the upregulation of Hes expression in the add mutant retina can be inhibited by the blockade of Wnt and Notch signaling, respectively. These data suggest that Hdac1 antagonizes these pathways to promote cell-cycle exit and the subsequent neurogenesis in zebrafish retina. Taken together, these data suggest that Hdac1 functions as a dual switch that suppresses both cell-cycle progression and inhibition of neurogenesis in the zebrafish retina.     

组蛋白去乙酰化酶CfSnt2调控果生刺盘孢生长发育和致病力

炭疽病是油茶Camellia oleifera的重要病害,该病害的优势致病菌是刺盘孢属Colletotrichum的果生刺盘孢C. fructicola,在全国的油茶产区普遍发生。我们前期发现组蛋白乙酰转移酶CfGcn5调控油茶果生刺盘孢的生长发育和致病过程,但组蛋白去乙酰化酶在该病菌中的生物学功能尚不清楚。本研究以组蛋白去乙酰化酶CfSnt2为研究对象,利用反向遗传学的方法,通过对野生型、CfSNT2基因敲除突变体及互补菌株的生物学表型进行比较分析,发现CfSNT2基因敲除突变体的菌丝生长速率明显减缓、分生孢子的产量显著减少、附着胞形成率降低、对细胞壁胁迫剂的响应异常,同时对油茶致病力显著减弱。以上现象说明CfSnt2调控果生刺盘孢的生长、产孢、附着胞的形成、对细胞壁完整性胁迫剂的耐受性及致病力。     

Histone deacetylase inhibitor activity in royal jelly might facilitate caste switching in bees

Worker and queen bees are genetically indistinguishable. However, queen bees are fertile, larger and have a longer lifespan than their female worker counterparts. Differential feeding of larvae with royal jelly controls this caste switching. There is emerging evidence that the queen-bee phenotype is driven by epigenetic mechanisms. In this study, we show that royal jelly--the secretion produced by the hypopharyngeal and mandibular glands of worker bees--has histone deacetylase inhibitor (HDACi) activity. A fatty acid, (E)-10-hydroxy-2-decenoic acid (10HDA), which accounts for up to 5% of royal jelly, harbours this HDACi activity. Furthermore, 10HDA can reactivate the expression of epigenetically silenced genes in mammalian cells. Thus, the epigenetic regulation of queen-bee development is probably driven, in part, by HDACi activity in royal jelly.