Small-molecule inhibitors of c-Myc transcriptional factor suppress proliferation and induce apoptosis of promyelocytic leukemia cell via cell cycle arrest.

c-Myc plays a decisive role in the proliferation of HL-60 promyelocytic leukemia cells. In the present study, we demonstrated that an inhibitor of c-Myc/Max/DNA complex formation has a high potentiality as a suppressor of c-Myc-involved cell signaling. We prepared recombinant c-Myc and Max proteins encompassing the human-origin DNA binding and dimerization domains, and tested a chemical library of 6480 small molecules for their inhibitory effect on the in vitro formation of the c-Myc/Max/DNA complex as well as their influence on DMSO-differentiated HL-60 cells.

Momordin I, an inhibitor of AP-1, suppressed osteoclastogenesis through inhibition of NF-kappaB and AP-1 and also reduced osteoclast activity and survival.

Osteoclasts originating from hematopoietic precursor cells differentiate into multinucleated cells through multiple steps. The essential roles of NF-kappaB and AP-1 in osteoclast differentiation have been clearly demonstrated in numerous studies. c-Fos, a component of AP-1 transcription factor, plays a key role in osteoclast differentiation.

Negative regulation of beta-catenin/Tcf signaling by naringenin in AGS gastric cancer cell.

Functional activation of beta-catenin/Tcf signaling plays an important role in early events in carcinogenesis. We examined the effect of naringenin against beta-catenin/Tcf signaling in gastric cancer cells. Reporter gene assay showed that naringenin inhibited beta-catenin/Tcf signaling efficiently.

Determination of the dissociation constants for recombinant c-Myc, Max, and DNA complexes: the inhibitory effect of linoleic acid on the DNA-binding step.

c-Myc, the protein product of protooncogene c-myc, functions in cell proliferation, differentiation, and neoplastic disease. In this study, recombinant c-Myc and Max proteins, encompassing DNA binding (basic region) and dimerization (helix-loop-helix/leucine zipper) domain of human origin, were expressed in bacteria as Myc87 and Max85. Myc87 was purified under denatured conditions and was renatured again.

Ionomycin downregulates beta-catenin/Tcf signaling in colon cancer cell line.

Functional activation of beta-catenin/Tcf signaling plays an important role in the early events in colorectal carcinogenesis. We examined the effect of ionomycin against beta-catenin/Tcf signaling in colon cancer cells. Reporter gene assay showed that ionomycin inhibited beta-catenin/Tcf signaling efficiently.

The inhibitory mechanism of curcumin and its derivative against beta-catenin/Tcf signaling.

We investigated the inhibitory mechanism of curcumin and its derivative (CHC007) against beta-catenin/T-cell factor (Tcf) signaling in various cancer cell lines. Curcumin is known to inhibit beta-catenin/Tcf transcriptional activity in HCT116 cells but not in SW620 cells. To clarify the inhibitory effect of curcumin against beta-catenin/Tcf signaling, we tested several cancer cell lines.

Inhibition of beta-catenin-mediated transactivation by flavanone in AGS gastric cancer cells.

Recently, data which prove that Wnt pathway activation may be an early event in multistep carcinogenesis in the stomach have been accumulating. We examined the effect of flavanone against beta-catenin/Tcf signaling in AGS gastric cancer cells. Reporter gene assay showed that flavanone inhibited beta-catenin/Tcf signaling efficiently.

Quercetin, a potent inhibitor against beta-catenin/Tcf signaling in SW480 colon cancer cells.

Dysregulation of Wnt/beta-catenin pathway plays a central role in early events in colorectal carcinogenesis. We examined the effect of quercetin, a famous anti-tumor agent, against beta-catenin/Tcf signaling in SW480 cells. Quercetin inhibited the transcriptional activity of beta-catenin/Tcf in SW480 and also in HEK293 cells transiently transfected with constitutively active mutant beta-catenin gene, whose product is not induced to be degraded by APC-Axin-GSK3beta complex, so we concluded that its inhibitory mechanism was related to beta-catenin itself or downstream components.

Alpha-synuclein has structural and functional similarities to small heat shock proteins.

The aggregation and fibrillization of alpha-synuclein, a major component of Lewy bodies, is a key event in Parkinson's disease. Although the mechanisms of fibrils formation are largely investigated, physiological function of alpha-synuclein is not yet clearly elucidated. Here, we showed that C-terminal region of alpha-synuclein is similar to alpha-crystalline domain of small heat shock proteins.

Synthetic curcumin analogs inhibit activator protein-1 transcription and tumor-induced angiogenesis.

In a previous study, we observed that some synthetic curcumin analogs inhibited complex formations between Fos-Jun heterodimer and activator protein-1 (AP-1) DNA. These curcumin analogs have been observed to repress the AP-1 transcription in AP-1-transfected cells and they also inhibited the increased expression of Jun/AP-1 protein by 12-O-tetradecanoylphorbol-13-acetate (TPA) in the same cells. After the AP-1 inhibition by curcumin analogs in TPA-treated HT-1080 human fibrosarcoma cells, a decrease in mRNA expression of c-jun and MMP3 (stromelysin-1) has been observed.

Structural basis for the selective inhibition of JNK1 by the scaffolding protein JIP1 and SP600125.

The c-jun N-terminal kinase (JNK) signaling pathway is regulated by JNK-interacting protein-1 (JIP1), which is a scaffolding protein assembling the components of the JNK cascade. Overexpression of JIP1 deactivates the JNK pathway selectively by cytoplasmic retention of JNK and thereby inhibits gene expression mediated by JNK, which occurs in the nucleus. Here, we report the crystal structure of human JNK1 complexed with pepJIP1, the peptide fragment of JIP1, revealing its selectivity for JNK1 over other MAPKs and the allosteric inhibition mechanism.

Inhibition of AP-1 transcription activator induces myc-dependent apoptosis in HL60 cells.

Transcriptional activation of AP-1 is intricately involved in cell proliferation and transformation. The natural product, nordihydroguaiaretic acid (NDGA) shows an inhibitory effect on the binding of jun/AP-1 protein to the AP-1 site in 12-O-tetradecanoylphorbol-13-acetate (TPA)-stimulated HL60 cells. The NDGA inhibits the auto-regulated de novo synthesis of c-jun mRNA in TPA-stimulated HL60 cells.

Determination of binding constant of transcription factor myc-max/max-max and E-box DNA: the effect of inhibitors on the binding.

The truncated myc and max proteins, only containing basic regions and helix-loop-helix/zipper (b/HLH/Zip) regions were over-expressed in E. coli and used for the determination of the binding constant and of the inhibitory mechanism on myc-max (or max-max)-DNA complex formation. The association kinetic constants (k(1) and k(-1)) of truncated max-max or myc-max dimer and DNA were determined as k(1)=(1.

7, 8-dihydroxyflavanone as an inhibitor for Jun-Fos-DNA complex formation and its cytotoxic effect on cultured human cancer cells.

7,8-Dihydroxyflavanone, isolated from the seeds of Alpinia Katsumadai Hayata, showed an inhibitory effect on Jun-Fos dimer action. 7,8-Dihydroxyflavanone blocked the action of the dimer on a DNA consensus sequence, the AP-1 binding site. We have concluded that the Jun-Fos heterodimer, bound with 7,8-dihydroxyflavanone, cannot bind to the AP-1 site and therefore results in signal interruption.

Garlic extract methylallyl thiosulfinate blocks insulin potentiation of platelet-derived growth factor-stimulated migration of vascular smooth muscle cells.

Platelet-derived growth factor (PDGF) is a potent inducer of vascular smooth muscle cell (VSMC) migration, whereas insulin, in physiological concentrations, helps maintain the nonproliferative phenotype of these cells. However, hyperinsulinemia (10 nmol/L) significantly potentiates the PDGF (30 pmol/L)-induced migration of VSMC. This potentiating effect of hyperinsulinemia appears to be mediated by increased availability of geranylgeranylated Rho-A.

Structural and functional implications of C-terminal regions of alpha-synuclein.

Aggregation of alpha-synuclein is thought to play a major role in the pathogenesis of Parkinson's disease (PD), which is characterized by the presence of intracytoplasmic Lewy bodies (LB) in the brain. alpha-Synuclein and its deletion mutants are largely unfolded proteins with random coil structures as revealed by CD spectra, fluorescence spectra, gel filtration chromatography, and ultracentrifugation. On the basis of its highly unfolded and flexible conformation, we have investigated the chaperone-like activity of alpha-synuclein in vitro.

Unsaturated fatty acids bind Myc-Max transcription factor and inhibit Myc-Max-DNA complex formation.

Oncoprotein Myc, hetero-dimerized with Max through a b/HLH/Zip region, is a transcription factor that governs important cellular processes such as cell cycle entry, proliferation and differentiation. We found that linoleic acid, isolated from Pollen Typhae, and other unsaturated fatty acids have strong inhibitory effects on the binding of Myc-Max heterodimer to an E-box DNA site (CA(C/T)GTG). The interaction of a fatty acid with a protein dimer, not with DNA, is assumed to block the entire Myc-Max-DNA complex formation.

QM, a putative tumor suppressor, regulates proto-oncogene c-yes.

The QM gene encodes a 24.5 kDa ribosomal protein L10 known to be highly homologous to a Jun-binding protein (Jif-1), which inhibits the formation of Jun-Jun dimers. Here we have carried out screening with the c-Yes protein and found that a QM homologous protein showed interactions with c-Yes and other Src family members.

New and known symmetrical curcumin derivatives inhibit the formation of Fos-Jun-DNA complex.

We previously reported that curcumin, the yellow pigment of turmeric, inhibited the formation of the Fos-Jun-DNA complex. Thus, we have synthesized 12 symmetrical curcuminoids. We used a slightly modified version of Pabon's method to search for an inhibitor more potent than curcumin.

Distinct roles of the N-terminal-binding domain and the C-terminal-solubilizing domain of alpha-synuclein, a molecular chaperone.

alpha-Synuclein, an acidic neuronal protein of 140 amino acids, is extremely heat-resistant and is natively unfolded. Recent studies have demonstrated that alpha-synuclein has chaperone activity both in vitro and in vivo, and that this activity is lost upon removing its C-terminal acidic tail. However, the detailed mechanism of the chaperone action of alpha-synuclein remains unknown.