Biomedical subjects

Hsiao-Ching Chuang

Publications and source records attributed to Hsiao-Ching Chuang.

4 recordsLinked to original sources

PubMed2006

Histone deacetylase 3 binds to and regulates the GCMa transcription factor.

Human GCMa transcription factor regulates expression of syncytin, a placental fusogenic protein mediating trophoblastic fusion. Recently, we have demonstrated that CBP-mediated GCMa acetylation underlies the activated cAMP/PKA signaling pathway that stimulates trophoblastic fusion. Because protein acetylation is a reversible modification governed by histone acetyltransferases (HATs) and histone deacetylase (HDACs), in this study we investigated the key HDACs responsible for deacetylation of GCMa and thus the reduction in GCMa activity to avoid unwanted fusion events that may have adverse effects on placental morphogenesis. We herein demonstrate that the HDAC inhibitor, trichostatin A (TSA), increases the level of acetylated GCMa and that HDAC1, 3, 4 and 5 interact with and deacetylate GCMa. Glutathione S-transferase (GST) pull-down assays further verified direct interaction between GCMa and HDAC3 or CBP and HDAC3. HDAC3 counteracts the transcriptional coactivator activity of CBP and the enhancement effect of CBP on GCMa-mediated transcriptional activation. Correlatively, we found in placental cells that HDAC3 associates with the proximal GCMa-binding site (pGBS) in the syncytin promoter and dissociates from pGBS in the presence of forskolin, which stimulates the association of CBP and GCMa with pGBS. Our studies support that trophoblastic fusion in placental morphogenesis depends on the regulation of GCMa activity by HAT and HDAC.

Binding Sites↗

PubMed2005

FBW2 targets GCMa to the ubiquitin-proteasome degradation system.

The GCM proteins GCMa/1 and GCMb/2 are novel zinc-containing transcription factors critical for glial cell differentiation in fly and for placental as well as parathyroid gland development in mouse. Previous pulse-chase experiments have demonstrated differential protein stabilities of GCM proteins with half-lives from approximately 30 min to 2 h (Tuerk, E. E., Schreiber, J., and Wegner, M. (2000) J. Biol. Chem. 275, 4774-4782). However, little is known about the machinery that controls GCM protein degradation. Here, we report the identification of an SCF complex as the GCM ubiquitin-protein isopeptide ligase (E3) that regulates human GCMa (hGCMa) degradation. We found that SKP1 and CUL1, two key components of the SCF complex, associate with hGCMa in vivo. We further identify the human F-box protein FBW2 (hFBW2) as the substrate recognition subunit in the SCF E3 complex for hGCMa. We show that hFBW2 interacts with hGCMa in a phosphorylation-dependent manner and promotes hGCMa ubiquitination. Supporting a critical role for hFBW2 in hGCMa degradation, knockdown of hFBW2 expression by RNA interference leads to a reduction in hGCMa ubiquitination and a concomitant increase in hGCMa protein stability. Our study identifies the SCF(hFBW2) E3 complex as the key machinery that targets hGCMa to the ubiquitin-proteasome degradation system.

Animals↗

PubMed2005

Stimulation of GCMa transcriptional activity by cyclic AMP/protein kinase A signaling is attributed to CBP-mediated acetylation of GCMa.

Human GCMa is a zinc-containing transcription factor primarily expressed in placenta. GCMa regulates expression of syncytin gene, which encodes for a placenta-specific membrane protein that mediates trophoblastic fusion and the formation of syncytiotrophoblast layer required for efficient fetal-maternal exchange of nutrients and oxygen. The adenylate cyclase activator, forskolin, stimulates syncytin gene expression and cell fusion in cultured placental cells. Here we present evidence that cyclic AMP (cAMP) signaling pathway activates the syncytin gene expression by regulating GCMa activity. We found that forskolin and protein kinase A (PKA) enhances GCMa-mediated transcriptional activation. Furthermore, PKA treatment stimulates the association of GCMa with CBP and increases GCMa acetylation. CBP primarily acetylates GCMa at lysine367, lysine406, and lysine409 in the transactivation domain (TAD). We found that acetylation of these residues is required to protect GCMa from ubiquitination and increases the TAD stability with a concomitant increase in transcriptional activity, supporting the importance of acetylation in PKA-dependent GCMa activation. Our results reveal a novel regulation of GCMa activity by cAMP-dependent protein acetylation and provide a molecular mechanism by which cAMP signaling regulates trophoblastic fusion.

Acetylation↗

PubMed2004

Polyacetylenes function as anti-angiogenic agents.

PURPOSE: To investigate the antiangiogenic effects of plant extracts and polyacetylenes isolated from Bidens pilosa Linn., which is a popular nutraceutical herbal tea and folk medicine in anti-inflammatory, antitumor, and other medications worldwide. METHODS: Anti-cell proliferation, anti-tube formation, and cell migration assays were used for the valuation of bioactivities of target plant extracts and phytocompounds against angiogenesis. Bioactivity-guided fractionation, HPLC, and various spectral analyses were used to identify active fraction and phytocompounds for anti-angiogenesis. RESULTS: We show that an ethyl acetate (EA) fraction of B. pilosa exhibited significant anti-cell proliferation and anti-tube formation activities against human umbilical vein endothelium cells (HUVEC). Bioassay-guided fractionation led to isolation of one new and one known polyacetylenes, 1,2-dihydroxytrideca-5,7,9,11-tetrayne (1) and 1,3-dihydroxy-6(E)- tetradecene-8,10,12-triyne (2), respectively, from the EA fraction. Compounds 1 and 2 manifested highly specific and significant activities against HUVEC proliferation with IC50 values of 2.5 and 0.375 microg/ml, respectively, however, compound 1 had a more potent effect on preventing tube formation of HUVEC than compound 2 at a dose of 2.5 microg/ml. Western blot analysis showed that both compounds upregulated p27(Kip) or p21(Cip1), cyclin-dependent kinase inhibitors, in HUVEC. CONCLUSIONS: This is the first report to demonstrate that polyacetylenes possess significant anti-angiogenic activities and the ability to regulate the expression of cell cycle mediators, for example, p27(Kip1), p21(Cip1), or cyclin E.

Acetylene↗