DAXX drives de novo lipogenesis and contributes to tumorigenesis.

Cancer cells exhibit elevated lipid synthesis. In breast and other cancer types, genes involved in lipid production are highly upregulated, but the mechanisms that control their expression remain poorly understood. Using integrated transcriptomic, lipidomic, and molecular studies, here we report that DAXX is a regulator of oncogenic lipogenesis.

Discovery of histone deacetylase 3 (HDAC3)-specific PROTACs.

Histone deacetylases (HDACs) are validated drug targets for cancer treatment. Increased HDAC isozyme selectivity and novel strategies to inhibit HDAC activity could lead to safer and more effective drug candidates. Nonetheless, it is quite challenging to develop isozyme-specific HDACi due to the highly conserved catalytic domain.

Inhibition of androgen receptor transactivation function by adenovirus type 12 E1A undermines prostate cancer cell survival.

Background: Mutations or truncation of the ligand-binding domain (LBD) of androgen receptor (AR) underlie treatment resistance for prostate cancer (PCa). Thus, targeting the AR N-terminal domain (NTD) could overcome such resistance.

Methods: Luciferase reporter assays after transient transfection of various DNA constructs were used to assess effects of E1A proteins on AR-mediated transcription.

Intrinsic cellular signaling mechanisms determine the sensitivity of cancer cells to virus-induced apoptosis.

Cancer cells of epithelial and mesenchymal phenotypes exhibit different sensitivities to apoptosis stimuli, but the mechanisms underlying this phenomenon remain partly understood. We constructed a novel recombinant adenovirus expressing Ad12 E1A (Ad-E1A12) that can strongly induce apoptosis. Ad-E1A12 infection of epithelial cancer cells displayed dramatic detachment and apoptosis, whereas cancer cells of mesenchymal phenotypes with metastatic propensity were markedly more resistant to this virus.

Identification of histone deacetylase inhibitors with benzoylhydrazide scaffold that selectively inhibit class I histone deacetylases.

Inhibitors of histone deacetylases (HDACi) hold considerable therapeutic promise as clinical anticancer therapies. However, currently known HDACi exhibit limited isoform specificity, off-target activity, and undesirable pharmaceutical properties. Thus, HDACi with new chemotypes are needed to overcome these limitations.

p53 SUMOylation promotes its nuclear export by facilitating its release from the nuclear export receptor CRM1.

Chromosomal region maintenance 1 (CRM1) mediates p53 nuclear export. Although p53 SUMOylation promotes its nuclear export, the underlying mechanism is unclear. Here we show that tethering of a small, ubiquitin-like modifier (SUMO) moiety to p53 markedly increases its cytoplasmic localization.

Small-molecule inhibitors of acetyltransferase p300 identified by high-throughput screening are potent anticancer agents.

Acetyltransferase p300 (KAT3B) plays key roles in signaling cascades that support cancer cell survival and sustained proliferation. Thus, p300 represents a potential anticancer therapeutic target. To discover novel anticancer agents that target p300, we conducted a high-throughput screening campaign.

Downregulation of Mdm2 and Mdm4 enhances viral gene expression during adenovirus infection.

Successful viral replication entails elimination or bypass of host antiviral mechanisms. Here, we show that shRNA-mediated knockdown of murine double minute (Mdm2) and its paralog Mdm4 enhanced the expression of early and late viral gene products during adenovirus (HAdV) infection. Remarkably, whereas the expression of HAdV genes was low in p53-deficient mouse embryonic fibroblasts (p53KO MEFs), the HAdV early gene products were efficiently expressed in Mdm2/p53 double-knockout (DKO) and Mdm4/p53 DKO MEFs, and viral capsid proteins were produced in Mdm2/p53 DKO MEFs.

Inhibition of p53 by adenovirus type 12 E1B-55K deregulates cell cycle control and sensitizes tumor cells to genotoxic agents.

Adenovirus E1B-55K represses p53-mediated transcription. However, the phenotypic consequence of p53 inhibition by E1B-55K for cell cycle regulation and drug sensitivity in tumor cells has not been examined. In HCT116 cells with constitutive E1B-55K expression, the activation of p53 target genes such as the p21, Mdm2, and Puma genes was attenuated, despite markedly elevated p53 protein levels.

Identification of two independent SUMO-interacting motifs in Daxx: evolutionary conservation from Drosophila to humans and their biochemical functions.

Daxx is essential for embryonic development and implicated in apoptosis and transcriptional regulation. It is found only in the animal kingdom and appears to arise first in insects. In the Drosophila genus, the Daxx orthologs are much larger than those in other species.

Repression of p53-mediated transcription by adenovirus E1B 55-kDa does not require corepressor mSin3A and histone deacetylases.

The Ad E1B 55-kDa protein (E1B) is a potent transcriptional repressor. In vitro biochemical studies revealed that direct p53-E1B interaction is essential for E1B to block p53-activated transcription and a corepressor may be involved. To understand how E1B represses p53-mediated transcription in vivo, we expressed E1B in several tumor cell lines that express wild type p53.

An EBF3-mediated transcriptional program that induces cell cycle arrest and apoptosis.

In a genome-wide screen for putative tumor suppressor genes, the EBF3 locus on the human chromosome 10q26.3 was found to be deleted or methylated in 73% of the examined cases of brain tumors. EBF3 is expressed in normal brain but is silenced in brain tumors.

Negative regulation of p53 functions by Daxx and the involvement of MDM2.

In normal cells p53 activity is tightly controlled and MDM2 is a known negative regulator. Here we show that via its acidic domain, Daxx binds to the COOH-terminal domain of p53, whose positive charges are critical for this interaction, as Lys to Arg mutations preserved, but Lys to Ala or Ser to Glu mutations abolished Daxx-p53 interaction. These results thus implicate acetylation and phosphorylation of p53 in regulating its binding to Daxx.

Sequestration of p53 in the cytoplasm by adenovirus type 12 E1B 55-kilodalton oncoprotein is required for inhibition of p53-mediated apoptosis.

The adenovirus E1B 55-kDa protein is a potent inhibitor of p53-mediated transactivation and apoptosis. The proposed mechanisms include tethering the E1B repression domain to p53-responsive promoters via direct E1B-p53 interaction. Cytoplasmic sequestration of p53 by the 55-kDa protein would impose additional inhibition on p53-mediated effects.

PCAF is a coactivator for p73-mediated transactivation.

The tumor suppressor p53-related p73 shares significant amino-acid sequence identity with p53. Like p53, p73 recognizes canonical p53 DNA-binding sites and activates p53-responsive target genes and induces apoptosis. Moreover, transcription coactivator p300/CBP binds to and coactivates with both p53 and p73 in stimulating the expression of their target genes.

Adenovirus E1B 55-kilodalton oncoprotein binds to Daxx and eliminates enhancement of p53-dependent transcription by Daxx.

The adenovirus E1B 55-kDa protein impairs the p53 pathway and enhances transformation, although the underlying mechanisms remain to be defined. We found that Daxx binds to the E1B 55-kDa protein in a yeast two-hybrid screen. The two proteins interact through their C termini.