Artificial genetic polymers against human pathologies.

Originally discovered by Nielsen in 1991, peptide nucleic acids and other artificial genetic polymers have gained a lot of interest from the scientific community. Due to their unique biophysical features these artificial hybrid polymers are now being employed in various areas of theranostics (therapy and diagnostics). The current review provides an overview of their structure, principles of rational design, and biophysical features as well as highlights the areas of their successful implementation in biology and biomedicine. Finally, the review discusses the areas of improvement that would allow their use as a new class of therapeutics in the future.

Activating Effect of 3-Benzylidene Oxindoles on AMPK: From Computer Simulation to High-Content Screening.

AMP-activated protein kinase (AMPK) is currently the subject of intensive study and active discussions. AMPK performs its functions both at the cellular level, providing the switch between energy-consuming and energy-producing processes, and at the whole body level, particularly, regulating certain aspects of higher nervous activity and behavior. Control of such a 'main switch' compensates dysfunctions and associated diseases. In the present paper, we studied the binding of 3-benzylidene oxindoles to the kinase domain of the AMPK α-subunit, which is thought to prevent its interaction with the autoinhibitory domain and thus result in the AMPK activation. For this purpose, we developed the cellular test system based on the AMPKAR plasmid, which implements the FRET effect, synthesized a number of 3-benzylidene oxindole compounds and simulated their binding to various sites of the kinase domain. The most probable binding site for the studied compounds was established by the correlation of calculated and experimental data. The obtained results allow to analyze various classes of AMPK activators using virtual and high-content screening.

Methylation-acetylation interplay activates p53 in response to DNA damage.

p53, an important tumor suppressor protein, exerts its function mostly as a sequence-specific transcription factor and is subjected to multiple posttranslational modifications in response to genotoxic stress. Recently, we discovered that lysine methylation of p53 at K372 by Set7/9 (also known as SET7 and Set9) is important for transcriptional activation and stabilization of p53. In this report we provide a molecular mechanism for the effect of p53 methylation on transcription. We demonstrate that Set7/9 activity toward p53, but not the nucleosomal histones, is modulated by DNA damage. Significantly, we show that lysine methylation of p53 is important for its subsequent acetylation, resulting in stabilization of the p53 protein. These p53 modification events can be observed on the promoter of p21 gene, a known transcriptional target of p53. Finally, we show that methylation-acetylation interplay in p53 augments acetylation of histone H4 in the promoter of p21 gene, resulting in its subsequent transcriptional activation and, hence, cell cycle arrest. Collectively, these results suggest that the cross talk between lysine methylation and acetylation is critical for p53 activation in response to DNA damage and that Set7/9 may play an important role in tumor suppression.

Transcription Factor IIA tau is associated with undifferentiated cells and its gene expression is repressed in primary neurons at the chromatin level in vivo.

The levels of General Transcription Factor (TF) IIA were examined during mammalian brain development and in rat embryo fibroblasts and transformed cell lines. The large TFIIA subunit paralogues alphabeta and tau are largely produced in unsynchronized cell lines, yet only TFIIA alphabeta is observed in a number of differentiated tissue extracts. Steady-state protein levels of the TFIIA tau, alphabeta, and gamma subunits were significantly reduced when human embryonal (ec) and hepatic carcinoma cell lines were stimulated to differentiate with either all-trans-retinoic acid (ATRA) or sodium butyrate. ATRA-treated NT2-ec cells required replating to induce a neuronal phenotype and loss of detectable TFIIA tau and gamma proteins. High levels of TFIIA tau, alphabeta, and gamma and Sp factors were identified in extracts from human fetal and rat embryonic day-18 brains, but not in human and rat adult brain extracts. A high histone H3 Lys9/Lys4 methylation ratio was observed in the TFIIA tau promoter of primary hippocampal neurons from day-18 rat embryos, suggesting that repressive epigenetic marks of chromatin prevent TFIIA tau from being transcribed in neurons. We conclude that TFIIA tau is associated with undifferentiated cells during development, yet is down-regulated at the chromatin level upon cellular differentiation.

Regulation of p53 activity through lysine methylation.

p53 is a tumour suppressor that regulates the cellular response to genotoxic stresses. p53 is a short-lived protein and its activity is regulated mostly by stabilization via different post-translational modifications. Here we report a novel mechanism of p53 regulation through lysine methylation by Set9 methyltransferase. Set9 specifically methylates p53 at one residue within the carboxyl-terminus regulatory region. Methylated p53 is restricted to the nucleus and the modification positively affects its stability. Set9 regulates the expression of p53 target genes in a manner dependent on the p53-methylation site. The crystal structure of a ternary complex of Set9 with a p53 peptide and the cofactor product S-adenosyl-l-homocysteine (AdoHcy) provides the molecular basis for recognition of p53 by this lysine methyltransferase.

Sp and GATA factors are critical for Apolipoprotein AI downstream enhancer activity in human HepG2 cells.

The factors that bind to the hepatic-specific human apolipoprotein AI (apoAI) 48-bp downstream enhancer (DSE) were identified and characterized by electrophoretic mobility shift assays. A significant homology was shown between the histone 4 (H4) promoters and the hepatic-specific human apoAI DSE at Sp1 and H4TF2 binding sites. Human HepG2 nuclear extracts were used to form four specific complexes with the DSE (referred to as apoAI DSE-1, -2, -3, and -4). The apoAI DSE-1 and -2 complexes showed similar binding specificity to the Sp/H4TF1 consensus site within the apoAI DSE. The apoAI DSE-1 complex was predominantly recognized by anti-Sp1 and Sp3 sera in gel shift assays, indicating that the DSE was recognized by multiple Sp family members. Nuclear extracts that were prepared from retinoic acid treated HepG2 cells showed increased levels of Sp factors in gel shift and Western blot assays. The apoAI DSE-2 complex was identified as H4TF1 and formed in the absence of magnesium chloride. The apoAI DSE-3 complex bound to a consensus GATA element within the DSE that was recognized by recombinant human GATA-6 as well. The apoAI DSE-3 complex was completely disrupted by a GATA-4 antibody in EMSA. GATA-4 and -6 were detected in nuclear extracts prepared from retinoic acid treated HepG2 cells using Western blot assays. The highest apoAI DSE-3 levels were observed with retinoic acid treated HepG2 cell nuclear extracts in EMSA. ApoAI DSE-4 is a multi-factor complex that includes an Sp/H4TF1 factor and either H4TF2 or apoAI DSE-3. Because apoAI DSE mutations revealed transcription defects in transient transfection assays, we conclude that the entire DSE sequence is required for full apoAI transcriptional activity in HepG2 cells.