Purification and characterization of recombinant CH3 domain fragment of the CREB-binding protein

The histone acetylation mediated by Gcn5 regulates the Hoxc11 gene expression in MEFs

Hox genes are responsible for encoding transcription factors that are essential for anterior-posterior body patterning at early stages of embryogenesis. However, detailed mechanisms of Hox genes are yet to be defined. Protein kinase B alpha (Akt1) was previously identified as a possible upstream regulator of Hox genes. Furthermore, the Hoxc11 gene has been upregulated in Akt1 null (Akt1-/-) mouse embryonic fibroblasts (MEFs), while repressed in wild-type MEFs. In this study, we propose to investigate the role of Gcn5, a histone acetyltransferase, in the regulation of Hoxc11 expression in MEFs. We showed that the H3 lysine 9 acetylation (H3K9ac) status has the same correlation with Hoxc11 expression and reported that Gcn5 is associated with the upregulation of Hoxc11 expression through H3K9ac in Akt1-/- MEFs. Since Hoxc11 was upregulated through histone acetylation in Akt1-/- MEFs, a functional role of Gcn5 on Hoxc11 expression was analyzed in Akt1-/- MEFs treated with Gcn5 specific inhibitor or transfected with Gcn5-small interfering RNA (Gcn5-siRNA). When the expression of Hoxc11 was analyzed using RT-PCR and real-time PCR, the Hoxc11 mRNA level was found to be similar in both Akt1-/- MEFs and control-siRNA transfected Akt1-/- MEFs. However, the Hoxc11 expression level was decreased in Gcn5-inhibited or Gcn5-knockdown Akt1-/- MEFs. Additionally, to analyze Gcn5-mediated histone acetylation status, chromatin immunoprecipitation assay was carried out in Gcn5-siRNA-transfected Akt1-/- MEFs. The H3K9ac at the Hoxc11 locus was decreased in Gcn5-knockdown Akt1-/- MEFs compared to controls. Based on these findings, we conclude that Gcn5 regulates Hoxc11 gene expression through mediating site-specific H3K9 acetylation in Akt1-/- MEFs.

Identification of Amino Acid Residues in Fibroblast Growth Factor 14 (FGF14) Required for Structure-Function Interactions with Voltage-gated Sodium Channel Nav1.6

The voltage-gated Na(+) (Nav) channel provides the basis for electrical excitability in the brain. This channel is regulated by a number of accessory proteins including fibroblast growth factor 14 (FGF14), a member of the intracellular FGF family. In addition to forming homodimers, FGF14 binds directly to the Nav1.6 channel C-tail, regulating channel gating and expression, properties that are required for intrinsic excitability in neurons. Seeking amino acid residues with unique roles at the protein-protein interaction interface (PPI) of FGF14·Nav1.6, we engineered model-guided mutations of FGF14 and validated their impact on the FGF14·Nav1.6 complex and the FGF14:FGF14 dimer formation using a luciferase assay. Divergence was found in the β-9 sheet of FGF14 where an alanine (Ala) mutation of Val-160 impaired binding to Nav1.6 but had no effect on FGF14:FGF14 dimer formation. Additional analysis revealed also a key role of residues Lys-74/Ile-76 at the N-terminal of FGF14 in the FGF14·Nav1.6 complex and FGF14:FGF14 dimer formation. Using whole-cell patch clamp electrophysiology, we demonstrated that either the FGF14(V160A) or the FGF14(K74A/I76A) mutation was sufficient to abolish the FGF14-dependent regulation of peak transient Na(+) currents and the voltage-dependent activation and steady-state inactivation of Nav1.6; but only V160A with a concomitant alanine mutation at Tyr-158 could impede FGF14-dependent modulation of the channel fast inactivation. Intrinsic fluorescence spectroscopy of purified proteins confirmed a stronger binding reduction of FGF14(V160A) to the Nav1.6 C-tail compared with FGF14(K74A/I76A) Altogether these studies indicate that the β-9 sheet and the N terminus of FGF14 are well positioned targets for drug development of PPI-based allosteric modulators of Nav channels.

Protein-protein interactions among signaling pathways may become new therapeutic targets in liver cancer (Review)

Numerous signaling pathways have been shown to be dysregulated in liver cancer. In addition, some protein-protein interactions are prerequisite for the uncontrolled activation or inhibition of these signaling pathways. For instance, in the PI3K/AKT signaling pathway, protein AKT binds with a number of proteins such as mTOR, FOXO1 and MDM2 to play an oncogenic role in liver cancer. The aim of the present review was to focus on a series of important protein-protein interactions that can serve as potential therapeutic targets in liver cancer among certain important pro-carcinogenic signaling pathways. The strategies of how to investigate and analyze the protein-protein interactions are also included in this review. A survey of these protein interactions may provide alternative therapeutic targets in liver cancer.