A combined study on structural, magnetic and specific heat on double perovskite iridates LnCoIrO[Ln = Pr, Nd].

We report rich magnetic behavior for Co-Ir based double perovskites consisting of different rare earth cations Pr and Nd: PrCoIrO(PCIO) and NdCoIrO(NCIO). Both oxides show an antisite disorder of 10% and a ferrimagnetic transition,FiMaround 96 K and 98 K respectively. The long range magnetic ordering is arising from the canted antiferromagnetic ordering between the Coand Irions.

Magnetic and transport properties of the mixed 3-5-4double perovskite SmCoIrO.

Iridium-based double perovskites having mixed 3-5-4magnetic sub-lattices are expected to exhibit exotic magnetic phenomenon. In this paper, we report a study of structural, magnetic and transport properties of the mixed 3-5-4double perovskite SmCoIrO(SMCO), which crystallizes in monoclinic structure with space group2/and the crystal symmetry remains same throughout the measured temperature down to 15 K. High resolution synchrotron x-ray diffraction reveals an isostructural phase transition around 104 K.

Dielectric and impedance spectroscopy of NdCoIrO double perovskite.

Polycrystalline NdCoIrO double perovskite crystallizes in monoclinic crystal structure with P2/n space group. The average grain size of powder sample is 400-500 nm. The dielectric, impedance and ac conductivity of the sample were studied in the temperature range 5-300 K and in the frequency range 20 Hz-2 MHz.

Observations of ferromagnetic cluster glass and exchange bias behavior in the double perovskite compound LaCuCrIrO.

LaCuIrO is a spin-orbit coupled Mott insulator, and shows a transition to noncollinear antiferromagnetic state from paramagnetic state below 74 K, and further into a weak ferromagnetic state below 54 K. Despite having two different magnetic phases, the LaCuIrO compound does not exhibit exchange bias phenomenon. In this present work, we report an experimental investigation on the structural and magnetic properties of the double perovskite compound LaCuCrIrO through high-resolution synchrotron x-ray diffraction, x-ray absorption near edge structure (XANES), and temperature and field-dependent magnetization measurements.

Spectroscopic and magnetic investigations of a spin-frustrated Mn-doped CoAlO spinel.

Single-phase polycrystalline spin-frustrated spinel oxides Co1-xMnxAl2O4 (0 ≤ x ≤ 0.3) have been prepared to investigate the optical and magnetic properties. Linear variation of the lattice parameter along with the characteristic hyperfine electron paramagnetic resonance (EPR) signal establish the fact that the Mn2+ ions are incorporated at Co2+ sites of the CoAl2O4 lattice.

Exchange bias effect in a finite site disordered canted antiferromagnet.

We report the temperature and magnetic field dependent magnetic properties of the single-phase polycrystalline LaSrCrRuO sample to explore the intrinsic magnetic phases of the sample. Our combined temperature and field dependent magnetization studies reveal the formation of ferromagnetic (FM) cluster-glass in the antiferromagnetic (AFM) matrix of host LaCrO. Interestingly, the as-studied sample exhibits both zero-field-cooled (horizontal shift) and field-cooled (vertical shift) exchange bias effects and, in both cases, magnitude of exchange bias field continuously increases with the decrease of temperature.

Mot1, Ino80C, and NC2 Function Coordinately to Regulate Pervasive Transcription in Yeast and Mammals.

Pervasive transcription initiates from cryptic promoters and is observed in eukaryotes ranging from yeast to mammals. The Set2-Rpd3 regulatory system prevents cryptic promoter function within expressed genes. However, conserved systems that control pervasive transcription within intergenic regions have not been well established.

EP400 Deposits H3.3 into Promoters and Enhancers during Gene Activation.

Gene activation in metazoans is accompanied by the presence of histone variants H2AZ and H3.3 within promoters and enhancers. It is not known, however, what protein deposits H3.

Fragile Nucleosomes Influence Pol II Promoter Function.

In this issue of Molecular Cell, Kubik et al. (2015) describe how the RSC chromatin remodeling complex collaborates with two DNA sequence motifs and sequence-specific general regulatory factors to assemble fragile nucleosomes at highly transcribed yeast Pol II promoters, and they distinguish these from promoters bearing stable nucleosomes.

The Ino80 complex prevents invasion of euchromatin into silent chromatin.

Here we show that the Ino80 chromatin remodeling complex (Ino80C) directly prevents euchromatin from invading transcriptionally silent chromatin within intergenic regions and at the border of euchromatin and heterochromatin. Deletion of Ino80C subunits leads to increased H3K79 methylation and noncoding RNA polymerase II (Pol II) transcription centered at the Ino80C-binding sites. The effect of Ino80C is direct, as it blocks H3K79 methylation by Dot1 in vitro.

Molecular basis of recognition of quadruplexes human telomere and c-myc promoter by the putative anticancer agent sanguinarine.

Background: Interaction of putative anticancer agent sanguinarine with two quadruplex forming sequences, human telomeric DNA (H24) and NHE III1 upstream of the P1 promoter of c-myc (Pu27), has been studied to understand the structural basis of the recognition.

Methods: Absorption, fluorescence and circular dichroism spectroscopy have been employed to characterize the association. Energetics of the interaction was studied by isothermal titration and differential scanning calorimetry.

The yeast cap binding complex modulates transcription factor recruitment and establishes proper histone H3K36 trimethylation during active transcription.

Recent studies have revealed a close relationship between transcription, histone modification, and RNA processing. In fact, genome-wide analyses that correlate histone marks with RNA processing signals raise the possibility that specific RNA processing factors may modulate transcription and help to "write" chromatin marks. Here we show that the nuclear cap binding complex (CBC) directs recruitment of transcription elongation factors and establishes proper histone marks during active transcription.

Human telomere d[(TTAGGG)4] undergoes a conformational transition to the Na+-form upon binding with sanguinarine in presence of K+.

Guanine-rich telomeric sequences fold into G-quadruplex conformation and are known to bind a variety of ligands including potential drug candidates. By means of CD spectroscopy and fluorescence lifetime measurements we demonstrate that putative anticancer therapeutic sanguinarine (SGR) exhibits two distinct interactions with human telomere d[(TTAGGG)(4)] (H24) in presence of K(+). Up to about 1:2 M ratio of H24:SGR (10 μM H24), two molecules of SGR bind H24.

Mechanism of interaction of small transcription inhibitors with DNA in the context of chromatin and telomere.

Small molecules from natural and synthetic sources have long been employed as human drugs. The transcription inhibitory potential of one class of these molecules has paved their use as anticancer drugs. The principal mode of action of these molecules is via reversible interaction with genomic DNA, double and multiple stranded.

Identification of a novel inhibitor of coactivator-associated arginine methyltransferase 1 (CARM1)-mediated methylation of histone H3 Arg-17.

Methylation of the arginine residues of histones by methyltransferases has important consequences for chromatin structure and gene regulation; however, the molecular mechanism(s) of methyltransferase regulation is still unclear, as is the biological significance of methylation at particular arginine residues. Here, we report a novel specific inhibitor of coactivator-associated arginine methyltransferase 1 (CARM1; also known as PRMT4) that selectively inhibits methylation at arginine 17 of histone H3 (H3R17). Remarkably, this plant-derived inhibitor, called TBBD (ellagic acid), binds to the substrate (histone) preferentially at the signature motif, "KAPRK," where the proline residue (Pro-16) plays a critical role for interaction and subsequent enzyme inhibition.

Inhibition of lysine acetyltransferase KAT3B/p300 activity by a naturally occurring hydroxynaphthoquinone, plumbagin.

Lysine acetyltransferases (KATs), p300 (KAT3B), and its close homologue CREB-binding protein (KAT3A) are probably the most widely studied KATs with well documented roles in various cellular processes. Hence, the dysfunction of p300 may result in the dysregulation of gene expression leading to the manifestation of many disorders. The acetyltransferase activity of p300/CREB-binding protein is therefore considered as a target for new generation therapeutics.

Sanguinarine interacts with chromatin, modulates epigenetic modifications, and transcription in the context of chromatin.

DNA-binding anticancer agents cause alteration in chromatin structure and dynamics. We report the dynamic interaction of the DNA intercalator and potential anticancer plant alkaloid, sanguinarine (SGR), with chromatin. Association of SGR with different levels of chromatin structure was enthalpy driven with micromolar dissociation constant.

Mechanism of p300 specific histone acetyltransferase inhibition by small molecules.

Dysfunction of histone acetyltransferases (HATs) leads to several diseases including cancer, diabetes, and asthma. Therefore, small molecule inhibitors and activators of HATs are being considered as new generation therapeutics. Here, we report the molecular mechanisms of p300 HAT inhibition by specific and nonspecific HAT inhibitors: garcinol, isogarcinol, and 1 (LTK14).

Chromatin as a target for the DNA-binding anticancer drugs.

Chemotherapy has been a major approach to treat cancer. Both constituents of chromatin, chromosomal DNA and the associated chromosomal histone proteins are the molecular targets of the anticancer drugs. Small DNA binding ligands, which inhibit enzymatic processes with DNA substrate, are well known in cancer chemotherapy.