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As a canonical cytoplasmic DNA sensor, cyclic GMP-AMP synthase (cGAS) plays a key role in innate immunity. In recent years, a growing number of studies have shown that cGAS can also be located in the nucleus and plays new functions such as regulating DNA damage repair, nuclear membrane repair, chromosome fusion, DNA replication, angiogenesis and other non-canonical functions. Meanwhile, the mechanisms underlying the nucleo-cytoplasmic transport and the regulation of cGAS activation have been revealed in recent years. Based on the current understanding of the structure, subcellular localization and canonical functions of cGAS, this review focuses on summarizing the mechanisms underlying nucleo-cytoplasmic transport, activity regulation and non-canonical functions of cGAS in the nucleus. We aim to provide insights into exploring the new functions of cGAS in the nucleus and advance its clinical translation., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Lu, Zhao, Chen, Wang, Liu and Liu.)

DNA nanomachines are becoming useful tools for molecular recognition, imaging, and diagnostics and have drawn gradual attention. Unfortunately, the present application of most DNA nanomachines is limited in vitro, so expanding their application in organism has become a primary focus. Hence, a novel DNA nanomachine named t-switch, based on the DNA duplex-triplex transition, is developed for monitoring the intracellular pH gradient. Our strategy is based on the DNA triplex structure containing C(+)-G-C triplets and pH-dependent Förster resonance energy transfer (FRET). Our results indicate that the t-switch is an efficient reporter of pH from pH 5.3 to 6.0 with a fast response of a few seconds. Also the uptake of the t-switch is speedy. In order to protect the t-switch from enzymatic degradation, PEI is used for modification of our DNA nanomachine. At the same time, the dynamic range could be extended to pH 4.6-7.8. The successful application of this pH-depended DNA nanomachine and motoring spatiotemporal pH changes associated with endocytosis is strong evidence of the possibility of self-assembly DNA nanomachine for imaging, targeted therapies, and controllable drug delivery.

Layer-by-layer (LbL) films containing cationic polyelectrolytes and anionic bioactive molecules such as DNA are promising biomaterials for controlled and localized gene delivery for a number of biomedical applications including cancer DNA vaccine delivery. Bioreducible LbL films made of disulfide-containing poly(amido amine)s (PAAs) and plasmid DNA can be degraded by redox-active membrane proteins through the thiol-disulfide exchange reaction to release DNA exclusively into the extracellular microenvironment adjacent to the film. In order to better understand the film degradation mechanism and nature of the released species, the bioreducible film degradation is studied by atomic force microscopy, fluorescence, and dynamic light scattering in solutions containing a reducing agent. The PAA/DNA LbL film undergoes fast bulk degradation with micrometer-sized pieces breaking off from the substrate. This bulk degradation behavior is arrested by periodic insertions of a nonbioreducible poly(ethylenimine) (PEI) layer. The LbL films containing PAA/DNA and PEI/DNA bilayers display sequential film disassembly and are capable of continuously releasing DNA nanoparticles over a prolonged time. Insertion of the PEI layer enables the bioreducible LbL films to transfect human embryonic kidney 293 cells. The data conclude that the PEI layer is effective as a barrier layer against interlayer diffusion during LbL film assembly and more importantly during film disassembly. Without the barrier layer, the high mobility of cleaved PAA fragments is responsible for bulk degradation of bioreducible LbL films, which may prevent their ultimate gene-delivery applications. This work establishes a direct link among film internal structure, disassembly mechanism, and transfection efficiency. It provides a simple method to design bioreducible LbL films for sequential and long-time DNA release.

A near-infrared light-responsive drug delivery platform based on Au-Ag nanorods (Au-Ag NRs) coated with DNA cross-linked polymeric shells was constructed. DNA complementarity has been applied to develop a polyacrylamide-based sol-gel transition system to encapsulate anticancer drugs into the gel scaffold. The Au-Ag NR-based nanogels can also be readily functionalized with targeting moieties, such as aptamers, for specific recognition of tumor cells. When exposed to NIR irradiation, the photothermal effect of the Au-Ag NRs leads to a rapid rise in the temperature of the surrounding gel, resulting in the fast release of the encapsulated payload with high controllability. In vitro study confirmed that aptamer-functionalized nanogels can be used as drug carriers for targeted drug delivery with remote control capability by NIR light with high spatial/temporal resolution.

We have developed a photoresponsive DNA-cross-linked hydrogel that can be photoregulated by two wavelengths with a reversible sol-gel conversion. This photoinduced conversion can be further utilized for precisely controllable encapsulation and release of multiple loads. Specifically, photosensitive azobenzene moieties are incorporated into DNA strands as cross-linkers, such that their hybridization to complementary DNAs (cDNAs) responds differently to different wavelengths of light. On the basis of the rheology variation of hydrogels, it is possible to utilize this material for storing and releasing molecules and nanoparticles. To prove the concept, three different materials--fluorescein, horseradish peroxidase, and gold nanoparticles--were encapsulated inside the gel at 450 nm and then released by photons at 350 nm. Further experiments were carried out to deliver the chemotherapy drug doxorubicin in a similar manner in vitro. Our results show a net release rate of 65% within 10 min, and the released drug maintained its therapeutic effect. This hydrogel system provides a promising platform for drug delivery in targeted therapy and in biotechnological applications.

An efficient pyrene-assisted method has been developed for the photolysis of disulfide bonds, with 77% of disulfides cleaved after only 20 min of irradiation (0.3W) at 350 nm. By employing a DNA framework, it was possible to observe both a distance-dependent cleavage pathway and a radical-forming photoreaction mechanism. To demonstrate the biomedical applications of such pyrene disulfide molecular assemblies, a DNA micelle structure and DNAzyme analog were further studied. Rapid photodriven disassembly of DNA micelles was achieved, allowing the further design of controlled pharmaceutical release at the target region and at a specific time. The DNAzyme analog can carry out multiple turnover reactions that follow the Michaelis-Menten equation, with a kcat of 10.2 min(-1) and a KM of 46.3 μM (0.3W 350 nm light source), comparable to that of common DNAzymes, e.g., 8-17 DNAzyme.

Functional nanomaterials based on molecular self-assembly hold great promise for applications in biomedicine and biotechnology. However, their efficacy could be a problem and can be improved by precisely controlling the size, structure, and functions. This would require a molecular engineering design capable of producing monodispersed functional materials characterized by beneficial changes in size, shape, and chemical structure. To address this challenge, we have designed and constructed a series of amphiphilic oligonucleotide molecules. In aqueous solutions, the amphiphilic oligonucleotide molecules, consisting of a hydrophilic oligonucleotide covalently linked to hydrophobic diacyllipid tails, spontaneously self-assemble into monodispersed, three-dimensional micellar nanostructures with a lipid core and a DNA corona. These hierarchical architectures are results of intermolecular hydrophobic interactions. Experimental testing further showed that these types of micelles have excellent thermal stability and their size can be fine-tuned by changing the length of the DNA sequence. Moreover, in the micelle system, the molecular recognition properties of DNA are intact, thus, our DNA micelles can hybridize with complimentary sequences while retaining their structural integrity. Importantly, when interacting with cell membranes, the highly charged DNA micelles are able to disintegrate themselves and insert into the cell membrane, completing the process of internalization by endocytosis. Interestingly, the fluorescence was found accumulated in confined regions of cytosole. Finally, we show that the kinetics of this internalization process is size-dependent. Therefore, cell permeability, combined with small sizes and natural nontoxicity are all excellent features that make our DNA-micelles highly suitable for a variety of applications in nanobiotechnology, cell biology, and drug delivery systems.

We report the design of a single-molecule nanomotor driven by photons. The nanomotor is a DNA hairpin-structured molecule incorporated with azobenzene moieties to facilitate reversible photocontrollable switching. Upon repeated UV-vis irradiation, this nanomotor displayed 40-50% open-close conversion efficiency. This type of nanomotor displays well-regulated responses and can be operated under mild conditions with no output of waste. In contrast to multiple-component DNA nanomachines, the intramolecular interaction in this single-molecule system offers unique concentration-independent motor functionality. Moreover, the hairpin structure of the motor backbone can significantly improve the efficiency of light-to-movement energy conversion. These results suggest that azobenzene-incorporated, hairpin-structured single-molecule DNA nanomotors have promising potential for applications which require highly efficient light-driven molecular motors.

Beyond its biological importance, short DNA sequences are of increasing interest as excellent and versatile building blocks, in material science and nanotechnology. DNA nanotechnology has been rapidly developed and has branched into several significantly different directions. Controlling DNA nanostructures is one of the most important branches, in which well-defined static nanostructures are constructed from rationally designed DNA motifs. The diversity and complexity of such DNA nanostructures also endow them with promising applications in nanofabrications, nanoelectronics, biodiagnostics, and DNA computations. In this review, we will summarize our recent efforts in this direction., (Copyright (c) 2007 Wiley-Liss, Inc.)

Sequence symmetry has been used to simplify the design of a DNA double-crossover (DX) molecule. The resulting DX molecule can self-assemble into two-dimensional (2D) crystalline arrays, but only requires two instead of otherwise four different DNA strands.

A three-point-star DNA motif has been designed and constructed, which can self-assemble into hexagonal two-dimensional lattices. The resulting lattices are up to 1 mm.

Accurate repair of DNA double-stranded breaks by homologous recombination preserves genome integrity and inhibits tumorigenesis. Cyclic GMP-AMP synthase (cGAS) is a cytosolic DNA sensor that activates innate immunity by initiating the STING-IRF3-type I IFN signalling cascade.sup.1,2. Recognition of ruptured micronuclei by cGAS links genome instability to the innate immune response.sup.3,4, but the potential involvement of cGAS in DNA repair remains unknown. Here we demonstrate that cGAS inhibits homologous recombination in mouse and human models. DNA damage induces nuclear translocation of cGAS in a manner that is dependent on importin-[alpha], and the phosphorylation of cGAS at tyrosine 215--mediated by B-lymphoid tyrosine kinase--facilitates the cytosolic retention of cGAS. In the nucleus, cGAS is recruited to double-stranded breaks and interacts with PARP1 via poly(ADP-ribose). The cGAS-PARP1 interaction impedes the formation of the PARP1-Timeless complex, and thereby suppresses homologous recombination. We show that knockdown of cGAS suppresses DNA damage and inhibits tumour growth both in vitro and in vivo. We conclude that nuclear cGAS suppresses homologous-recombination-mediated repair and promotes tumour growth, and that cGAS therefore represents a potential target for cancer prevention and therapy.DNA damage induces translocation of cyclic GMP-AMP synthase to the nucleus, where it suppresses homologous recombination by interfering with the formation of the PARP1-Timeless complex., Author(s): Haipeng Liu [sup.1] [sup.2] , Haiping Zhang [sup.3] , Xiangyang Wu [sup.1] [sup.2] , Dapeng Ma [sup.2] , Juehui Wu [sup.1] [sup.2] , Lin Wang [sup.1] [sup.2] , Yan [...]

Gelungene Modifizierung: Zelloberflächen können auf einfache Weise mit zielspezifischen Liganden wie DNA ‐ Aptameren versehen werden, wobei die Auswirkungen auf die modifizierten Zellen minimal gehalten werden. Nach Inkubation mit Lipoaptamer ‐ Sonden erkennen Immunzellen (rot, siehe Schema) in einer Zellmischung Krebszellen (blau) und zerstören diese. [ABSTRACT FROM AUTHOR]