Procyanidin B3, an inhibitor of histone acetyltransferase, enhances the action of antagonist for prostate cancer cells via inhibition of p300-dependent acetylation of androgen receptor

Increasing evidence suggests that AR (androgen receptor) acetylation is critical for prostate cancer cell growth. In the present study, we identified Pro-B3 (procyanidin B3) as a specific HAT (histone acetyltransferase) inhibitor. Pro-B3 selectively inhibited the activity of HATs, but not other epigenetic enzymes. Pro-B3 substantially inhibited the p300-mediated AR acetylation, both in vitro and in vivo. Pro-B3 inhibited both p300-dependent and agonist-induced AR transcription. We demonstrate that the p300-mediated AR acetylation is critical for the hormone responsiveness of AR. Interestingly, B3 treatment efficiently enhanced the antagonist activity of flutamide through suppression of p300 HAT activity, demonstrating that relative p300 activity is critical for the antagonist action. Finally, Pro-B3 treatment inhibited acetylation-dependent prostate cell proliferation and expression of cell-cycle control genes, subsequently increasing cell death, indicating the functional importance of AR acetylation for prostate cancer cell growth.ope

The functional relationship between co-repressor N-CoR and SMRT in mediating transcriptional repression by thyroid hormone receptor alpha.

A central issue in mediating repression by nuclear hormone receptors is the distinct or redundant function between co-repressors N-CoR (nuclear receptor co-repressor) and SMRT (silencing mediator of retinoid and thyroid hormone receptor). To address the functional relationship between SMRT and N-CoR in TR (thyroid hormone receptor)-mediated repression, we have identified multiple TR target genes, including BCL3 (B-cell lymphoma 3-encoded protein), Spot14 (thyroid hormone-inducible hepatic protein), FAS (fatty acid synthase), and ADRB2 (beta-adrenergic receptor 2). We demonstrated that siRNA (small interfering RNA) treatment against either N-CoR or SMRT is sufficient for the de-repression of multiple TR target genes. By the combination of sequence mining and physical association as determined by ChIP (chromatin immunoprecipitation) assays, we mapped the putative TREs (thyroid hormone response elements) in BCL3, Spot14, FAS and ADRB2 genes. Our data clearly show that SMRT and N-CoR are independently recruited to various TR target genes. We also present evidence that overexpression of N-CoR can restore repression of endogenous genes after knocking down SMRT. Finally, unliganded, co-repressor-free TR is defective in repression and interacts with a co-activator, p300. Collectively, these results suggest that both SMRT and N-CoR are limited in cells and that knocking down either of them results in co-repressor-free TR and consequently de-repression of TR target genes.ope

Epigallocatechin-3-gallate, a histone acetyltransferase inhibitor, inhibits EBV-induced B lymphocyte transformation via suppression of RelA acetylation.

Because the p300/CBP-mediated hyperacetylation of RelA (p65) is critical for nuclear factor-kappaB (NF-kappaB) activation, the attenuation of p65 acetylation is a potential molecular target for the prevention of chronic inflammation. During our ongoing screening study to identify natural compounds with histone acetyltransferase inhibitor (HATi) activity, we identified epigallocatechin-3-gallate (EGCG) as a novel HATi with global specificity for the majority of HAT enzymes but with no activity toward epigenetic enzymes including HDAC, SIRT1, and HMTase. At a dose of 100 micromol/L, EGCG abrogates p300-induced p65 acetylation in vitro and in vivo, increases the level of cytosolic IkappaBalpha, and suppresses tumor necrosis factor alpha (TNFalpha)-induced NF-kappaB activation. We also showed that EGCG prevents TNFalpha-induced p65 translocation to the nucleus, confirming that hyperacetylation is critical for NF-kappaB translocation as well as activity. Furthermore, EGCG treatment inhibited the acetylation of p65 and the expression of NF-kappaB target genes in response to diverse stimuli. Finally, EGCG reduced the binding of p300 to the promoter region of interleukin-6 gene with an increased recruitment of HDAC3, which highlights the importance of the balance between HATs and histone deacetylases in the NF-kappaB-mediated inflammatory signaling pathway. Importantly, EGCG at 50 micromol/L dose completely blocks EBV infection-induced cytokine expression and subsequently the EBV-induced B lymphocyte transformation. These results show the crucial role of acetylation in the development of inflammatory-related diseasesope

HDAC3 전사억제자 복합체들의 다양한 생물학적 기능 규명

의과학과/박사[한글] [영문]The reversible acetylation by HDAC and HAT is known to be crucial for the stability of p53 and p53-dependent apoptotic signaling. To unravel the functional significance of HDAC3 involved in apoptosis, the yeast-two hybrid assay was performed, and finally identified the proapototic protein, PDCD5 as a novel-HDAC3 interacting protein. Diverse protein-protein interacting analysis found that PDCD5 selectively interacts with HDAC3 among class I HDACs. This study shows that PDCD5-mediated HDAC3 cleavage upon apoptotic stress is dependent on caspase-3. Depletion of either PDCD5 or caspase-3 failed to induce the HDAC3-cleavage and diverse apototic event, indicating that PDCD5-capspase-3 cascade is generally essential for apoptosis. Furthermore, PDCD3-caspase-3 complex directly mediates the ectoposide-induced HDAC3 cleavage and reduction of histone deacetylase activity, and finally increase of cytoplasmic accumulation of HDAC3. More importantly, caspase-3-dependent HDAC3 cleavage by PDCD5 act as a modulator for the maintenance of p53 acetylation and stability.prohibitio

Grape seed extract regulates androgen receptor-mediated transcription in prostate cancer cells through potent anti-histone acetyltransferase activity.

Histone acetylation, which is regulated by histone acetyltransferases (HATs) and deacetylases, is an epigenetic mechanism that influences eukaryotic transcription. Significant changes in histone acetylation are associated with cancer; therefore, manipulating the acetylation status of key gene targets is likely crucial for effective cancer therapy. Grape seed extract (GSE) has a known protective effect against prostate cancer. Here, we showed that GSE significantly inhibited HAT activity by 30-80% in vitro (P < .05). Furthermore, we demonstrated significant repression of androgen receptor (AR)-mediated transcription by GSE in prostate cancer cells by measuring luciferase activity using a pGL3-PSA construct bearing the AR element in the human prostate cancer cell line LNCaP (P < .05). GSE treatment also decreased the mRNA level of the AR-regulated genes PSA and NKX 3.1. Finally, GSE inhibited growth of LNCaP cells. These results indicate that GSE potently inhibits HAT, leading to decreased AR-mediated transcription and cancer cell growth, and implicate GSE as a novel candidate for therapeutic activity against prostate cancer.ope

Delphinidin, a specific inhibitor of histone acetyltransferase, suppresses inflammatory signaling via prevention of NF-κB acetylation in fibroblast-like synoviocyte MH7A cells.

Histone acetyltransferase (HAT) inhibitors (HATi) isolated from dietary compounds have been shown to suppress inflammatory signaling, which contributes to rheumatoid arthritis. Here, we identified a novel HATi in Punica granatum L. known as delphinidin (DP). DP did not affect the activity of other epigenetic enzymes (histone deacetylase, histone methyltransferase, or sirtuin1). DP specifically inhibited the HAT activities of p300/CBP. It also inhibited p65 acetylation in MH7A cells, a human rheumatoid arthritis synovial cell line. DP-induced hypoacetylation was accompanied by cytosolic accumulation of p65 and nuclear localization of IKBα. Accordingly, DP treatment inhibited TNFα-stimulated increases in NF-κB function and expression of NF-κB target genes in these cells. Importantly, DP suppressed lipopolysaccharide-induced pro-inflammatory cytokine expression in Jurkat T lymphocytes, demonstrating that HATi efficiently suppresses cytokine-mediated immune responses. Together, these results show that the HATi activity of DP counters anti-inflammatory signaling by blocking p65 acetylation and that this compound may be useful in preventing inflammatory arthritis.ope

Gallic acid suppresses lipopolysaccharide-induced nuclear factor-kappaB signaling by preventing RelA acetylation in A549 lung cancer cells

Although multiple studies have revealed that gallic acid plays an important role in the inhibition of malignant transformation, cancer development, and inflammation, the molecular mechanism of gallic acid in inflammatory diseases is still unclear. In this study, we identified gallic acid from Rosa rugosa as a histone acetyltransferase (HAT) inhibitor with global specificity for the majority of HAT enzymes, but with no activity toward epigenetic enzymes including sirtuin (silent mating type information regulation 2 homologue) 1 (S. cerevisiae), histone deacetylase, and histone methyltransferase. Enzyme kinetic studies indicated that gallic acid uncompetitively inhibits p300/CBP-dependent HAT activities. We found that gallic acid inhibits p300-induced p65 acetylation, both in vitro and in vivo, increases the level of cytosolic IkappaBalpha, prevents lipopolysaccharide (LPS)-induced p65 translocation to the nucleus, and suppresses LPS-induced nuclear factor-kappaB activation in A549 lung cancer cells. We have also shown that gallic acid treatment inhibits the acetylation of p65 and the LPS-induced serum levels of interleukin-6 in vivo. Importantly, gallic acid generally inhibited inflammatory responses caused by other stimuli, including LPS, IFN-gamma, and interleukin-1beta, and further downregulated the expression of nuclear factor-kappaB-regulated antiapoptotic genes. These results show the crucial role of acetylation in the development of inflammatory diseases.ope

Effect of anti-histone acetyltransferase activity from Rosa rugosa Thunb. (Rosaceae) extracts on androgen receptor-mediated transcriptional regulation

ETHNOPHARMACOLOGICAL RELEVANCE: Rosa rugosa Thunb. (Rosaceae) has been traditionally used for treatments of diabetes, chronic inflammatory diseases, pain, and anticancer in Korea. AIM OF STUDY: We investigate the inhibitory effect of histone acetyltransferase activity from the methanol extract of stems of Rosa rugosa on androgen receptor-mediated transcriptional regulation. MATERIALS AND METHODS: For the present study, Rosa rugosa methanol extract (RRME) was obtained from stem part of Rosa rugosa using methanol extraction. Histone acetyltransferase assay were performed to measure the inhibitory effect on acetylation, reporter assay, real-time PCR and ChIP assay were performed to measure androgen receptor-mediated transcriptional regulation, and MTT test were performed to measure cell viability. RESULTS: RRME inhibited both p300 and CBP (60-70% at 100 microg/ml) activity. We show RRME mediates agonist-dependent androgen receptor (AR) activation and suppresses antagonist-dependent inhibition. RRME treatment also decreased transcription of AR regulated genes and also reduced histone H3 and AR acetylation in the promoters of prostate-specific antigen (PSA) and beta-2-microglobulin (B2M). Finally, RRME treatment reduced the growth of LNCaP, a human prostate cancer cell line. CONCLUSION: These results demonstrate RRME is a potent HAT inhibitor, which reduced AR and histone acetylation leading to decreased AR-mediated transcription and reduced LNCaP cell growth.ope

Exploring A Research Trend on Entrepreneurial Ecosystem in the 40 Years of the Asia Pacific Journal of Small Business for the Development of Ecosystem Measurement Framework

본 논문은 한국중소기업학회 40년의 역사적 흐름 속에서창업생태계 연구 동향을 조명하고, 생산적 창업생태계 조성에 필요한 생태투입․산출요인에 관한 측정지표 개발 방향을 고찰하기 위해 수행되었다. ‘중소기업연구’의 창업생태계연구 동향을 살펴본 결과, 선행연구는 생산적 창업생태계 조성과 다양한 생태투입요인에대한 관리적 중요성을 강조하고 있다. 그러나 생태투입요인과 기업가정신으로 대변되는생태산출요인 간 인과성을 검증하려는 실증연구에 필요한 측정모형 및 변수개발을 다루는탐색적 연구는 실무․정책적 요구를 충족하지 못하고 있었다. 경험적 사실에 근거하여창업생태계 성공요건을 규명하는 사례연구의 불균형적 발전은 연구 결과의 일반화와효과적 실무․정책적 대안을 제안하는 데 한계가 있다. 국가․지역 경제성장을 견인하는혁신동력으로써 생산적 창업생태계의 조성과 효율적 운영이 중요한 오늘날, 향후 실증연구에서 활용 가능한 생태요인 측정모형의 개발이 절실하다. 이에 본 연구는 기존의 [투입→산출→결과→성과] 프로세스를 적용하여, 생태투입․산출요인을 중심으로 창업생태계 측정모형을 개념화하였다. 우선, 선행연구를 기반으로 생태투입요인(재정적․지식․제도적․ 사회적 자본)을 체계화하고, 생태산출요인은 설립, 혁신 및 성과기준 기업가정신으로개념화하여 측정 가능한 변수로 도출하였다. 또한, 향후 실증연구에서 생태투입․산출요인측정 시 활용 가능한 데이터베이스를 제안하고, 각 데이터의 특성을 검토하였다. 본 연구가제안한 창업생태계 측정지표는 생태요인 간 인과성을 검증하려는 후속 연구에서 활용가치가 높을 것으로 기대된다.22Nkc