Cobalt(II), copper(II) and zinc(II) complexes of di-2-pyridyl ketone-4- methoxybenzhydrazone: Preparation and characterization

745-752A new aroylhydrazone ligand, di-2-pyridyl ketone-4-methoxybenzhydrazone (DKMBH∙H2O) and its three complexes with cobalt(II), copper(II) and zinc(II), labelled Co(DKMB)Cl (1), Cu(DKMB)Cl (2), and Zn(DKMB)Cl (3) have been prepared and structurally studied. The spectroscopic techniques like IR, UV-Vis, MS, and 1H NMR, as well as CHN analysis and thermal analysis, have been used to physico-chemically characterize the synthesized compounds. The IR and 1H NMR analyses have made clear that the aroylhydrazone remains in the amido form in the solid state. The IR spectral measurements further support the tridentate character of the NNO donor aroylhydrazone. In all complexes, pyridine nitrogen, azomethine nitrogen, and iminolate oxygen of the tridentate aroylhydrazone are involved to coordinate to the metal centre

HIV integrase inhibitor, Elvitegravir, impairs RAG functions and inhibits V(D)J recombination

Integrase inhibitors are a class of antiretroviral drugs used for the treatment of AIDS that target HIV integrase, an enzyme responsible for integration of viral cDNA into host genome. RAG1, a critical enzyme involved in V(D)J recombination exhibits structural similarity to HIV integrase. We find that two integrase inhibitors, Raltegravir and Elvitegravir, interfered with the physiological functions of RAGs such as binding, cleavage and hairpin formation at the recombination signal sequence (RSS), though the effect of Raltegravir was limited. Circular dichroism studies demonstrated a distinct change in the secondary structure of RAG1 central domain (RAG1 shares DDE motif amino acids with integrases), and when incubated with Elvitegravir, an equilibrium dissociation constant (K-d) of 32.53 +/- 2.9 mu M was determined by Biolayer interferometry, leading to inhibition of its binding to DNA. Besides, using extrachromosomal assays, we show that Elvitegravir inhibited both coding and signal joint formation in pre-B cells. Importantly, treatment with Elvitegravir resulted in significant reduction of mature B lymphocytes in 70% of mice studied. Thus, our study suggests a potential risk associated with the use of Elvitegravir as an antiretroviral drug, considering the evolutionary and structural similarities between HIV integrase and RAGs

The Conserved ATM Kinase RAG2-S365 Phosphorylation Site Limits Cleavage Events in Individual Cells Independent of Any Repair Defect

Summary: Many DNA lesions associated with lymphoid malignancies are linked to off-target cleavage by the RAG1/2 recombinase. However, off-target cleavage has mostly been analyzed in the context of DNA repair defects, confounding any mechanistic understanding of cleavage deregulation. We identified a conserved SQ phosphorylation site on RAG2 365 to 366 that is involved in feedback control of RAG cleavage. Mutation of serine 365 to a non-phosphorylatable alanine permits bi-allelic and bi-locus RAG-mediated breaks in the same cell, leading to reciprocal translocations. This phenomenon is analogous to the phenotype we described for ATM kinase inactivation. Here, we establish deregulated cleavage itself as a driver of chromosomal instability without the associated repair defect. Intriguingly, a RAG2-S365E phosphomimetic rescues the deregulated cleavage of ATM inactivation, reducing the incidence of reciprocal translocations. These data support a model in which feedback control of cleavage and maintenance of genome stability involves ATM-mediated phosphorylation of RAG2. : DNA lesions associated with lymphoid malignancies are linked to off-target cleavage by the RAG1/2 recombinase. Off-target RAG cleavage has only been analyzed in the context of DNA repair defects. Here, Hewitt et al. identify a phosphorylation site on RAG2 that controls RAG cleavage to maintain genome stability independent of a repair defect. Keywords: RAG cleavage regulation, genome stability, V(D)J recombination, ATM, RAG2S365, reciprocal translocations, developing lymphocyte

RNA Interactions Are Essential for CTCF-Mediated Genome Organization

The function of the CCCTC-binding factor (CTCF) in the organization of the genome has become an important area of investigation, but the mechanisms by which CTCF dynamically contributes to genome organization are not clear. We previously discovered that CTCF binds to large numbers of endogenous RNAs, promoting its self-association. In this regard, we now report two independent features that disrupt CTCF association with chromatin: inhibition of transcription and disruption of CTCF-RNA interactions through mutations of 2 of its 11 zinc fingers that are not required for CTCF binding to its cognate DNA site: zinc finger 1 (ZF1) or zinc finger 10 (ZF10). These mutations alter gene expression profiles as CTCF mutants lose their ability to form chromatin loops and thus the ability to insulate chromatin domains and to mediate CTCF long-range genomic interactions. Our results point to the importance of CTCF-mediated RNA interactions as a structural component of genome organization