A G-quadruplex (G4) is a well-known nucleic acid secondary structure comprising guanine-rich sequences, and has profound implications for various pharmacological and biological events, including cancers. Therefore, ligands interacting with G4s have attracted great attention as potential anticancer therapies or in molecular probe applications. To date, a large variety of DNA/RNA G4 ligands have been developed by a number of laboratories. As protein-targeting drugs face similar situations, G-quadruplex-interacting drugs displayed low selectivity to the targeted G-quadruplex structure. This low selectivity could cause unexpected effects that are usually reasons to halt the drug development process. In this review, we address the recent research on synthetic G4 DNA-interacting ligands that allow targeting of selected G4s as an approach toward the discovery of highly effective anticancer drugs.
An amputated cricket leg regenerates all missing parts with normal size and shape, indicating that regenerating blastemal cells are aware of both their position and the normal size of the leg. However, the molecular mechanisms regulating this process remain elusive. Here, we use a cricket model to show that the Dachsous/Fat (Ds/Ft) signalling pathway is essential for leg regeneration. We found that knockdown of ft or ds transcripts by regeneration-dependent RNA interference (rdRNAi) suppressed proliferation of the regenerating cells along the proximodistal (PD) axis concomitantly with remodelling of the pre-existing stump, making the regenerated legs shorter than normal. By contrast, knockdown of the expanded (ex) or Merlin (Mer) transcripts induced overproliferation of the regenerating cells, making the regenerated legs longer. These results are consistent with those obtained using rdRNAi during intercalary regeneration induced by leg transplantation. We present a model to explain our results in which the steepness of the Ds/Ft gradient controls growth along the PD axis of the regenerating leg.
A G-quadruplex is a nucleic acid secondary structure that is adopted by guanine-rich sequences, and is considered to be relevant in various pharmacological and biological contexts. G-Quadruplexes have also attracted great attention in the field of DNA nanotechnology because of their extremely high thermal stability and the availability of many defined structures. To date, a large repertory of DNA/RNA G-quadruplex-interactive ligands has been developed by numerous laboratories. Several relevant reviews have also been published that have helped researchers to grasp the full scope of G-quadruplex research from its outset to the present. This review focuses on the G-quadruplex ligands that allow targeting of specific G-quadruplexes. Moreover, unique ligands, successful methodologies, and future perspectives in relation to specific G-quadruplex recognition are also addressed.
In addition to the Watson-Crick double helix, secondary DNA structures are thought to play important roles in a variety of biological processes. One important example is the G-quadruplex structure that is formed at the chromosome ends, which inhibits telomerase activity by blocking its access to telomeres. G-quadruplex structures represent a new class of molecular targets for DNA-interactive compounds that may be useful to target telomeres. Here, we reported the first example of enantioselective recognition of quadruplex DNA by a chiral cyclic helicene. We propose a new ligand-binding cleft between two telomeric human G-quadruplexes linked by a TTA linker. We found that the cyclic helicene M1 exhibited potent inhibitory activity against telomerase.
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