Mitoxantrone and Analogues Bind and Stabilize i-Motif Forming DNA Sequences

YesThere are hundreds of ligands which can interact with G-quadruplex DNA, yet very few which target i-motif. To appreciate an understanding between the dynamics between these structures and how they can be affected by intervention with small molecule ligands, more i-motif binding compounds are required. Herein we describe how the drug mitoxantrone can bind, induce folding of and stabilise i-motif forming DNA sequences, even at physiological pH. Additionally, mitoxantrone was found to bind i-motif forming sequences preferentially over double helical DNA. We also describe the stabilisation properties of analogues of mitoxantrone. This offers a new family of ligands with potential for use in experiments into the structure and function of i-motif forming DNA sequences

The Tandem CARDs of NOD2: Intramolecular Interactions and Recognition of RIP2

Caspase recruitment domains (CARDs) are homotypic protein interaction modules that link the stimulus-dependent assembly of large signaling platforms such as inflammasomes to the activation of downstream effectors that often include caspases and kinases and thereby play an important role in the regulation of inflammatory and apoptotic signaling pathways. NOD2 belongs to the NOD-like (NLR) family of intracellular pattern recognition receptors (PRR) and induces activation of the NF-κB pathway in response to the recognition of bacterial components. This process requires the specific recognition of the CARD of the protein kinase RIP2 by the tandem CARDs of NOD2. Here we demonstrate that the tandem CARDs of NOD2 are engaged in an intramolecular interaction that is important for the structural stability of this region. Using a combination of ITC and pull-down experiments we identify distinct surface areas that are involved in the intramolecular tandem CARD interaction and the interaction with the downstream effector RIP2. Our findings indicate that while CARDa of NOD2 might be the primary binding partner of RIP2 the two CARDs of NOD2 do not act independently of one another but may cooperate to from a binding surface that is distinct from that of single CARDs

Crystal structure of parallel quadruplexes from human telomeric DNA

Telomeric ends of chromosomes, which comprise noncoding repeat sequences of guanine-rich DNA, are fundamental in protecting the cell from recombination and degradation(1). Disruption of telomere maintenance leads to eventual cell death, which can be exploited for therapeutic intervention in cancer. Telomeric DNA sequences can form four-stranded (quadruplex) structures(2-4), which may be involved in the structure of telomere ends(5). Here we describe the crystal structure of a quadruplex formed from four consecutive human telomeric DNA repeats and grown at a K+ concentration that approximates its intracellular concentration. K+ ions are observed in the structure. The folding and appearance of the DNA in this intramolecular quadruplex is fundamentally different from the published Na+-containing quadruplex structures(2,4,6). All four DNA strands are parallel, with the three linking trinucleotide loops positioned on the exterior of the quadruplex core, in a propeller-like arrangement. The adenine in each TTA linking trinucleotide loop is swung back so that it intercalates between the two thymines. This DNA structure suggests a straightforward path for telomere folding and unfolding, as well as ways in which it can recognize telomere-associated proteins

Development of LNA gapmer oligonucleotide-based therapy for ALS/FTD caused by the C9orf72 repeat expansion

Several neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS), have a complex genetic background, in addition to cases where the disease appears to manifest sporadically. The recent discovery of the hexanucleotide repeat expansion in the C9orf72 gene as the causative agent of ALS (C9ALS) gives rise to the opportunity to develop new therapies directed at this mutation, which is responsible for a large proportion of ALS and/or frontotemporal dementia cases. Mammalian models conscientiously replicating the late-onset motor defects and cellular pathologies seen in human patients do not exist. In this context, patient-derived cells give us a platform to test potential antisense oligonucleotide therapies, which could be the key to treat this subtype of motor neuron disease. Recently, we described that locked nucleic acid gapmer oligonucleotide-based treatment targeting C9orf72 repeat expanded transcripts resulted in recovery from the disease-related phenotypes in patient-derived fibroblasts. Our findings highlight the therapeutic potential of C9ALS using this gapmer oligonucleotide-based approach