Photocontrol of Single‐Chain DNA Conformation in Cell‐Mimicking Microcompartments

Abstract

It has been well established that the regulation of gene activity is strongly dependent on the higher-order structure of genomic DNA molecules.[1] Several strategies have thus been developed to control the higher-order structure of long DNA molecules. Most of them have been based on the use of chemical compounds that bind to DNA to neutralize its charge, such as polyamines, multivalent metal cations, cationic surfactants, cationic polymers, nanoparticles, or crowding agents such as hydrophilic polymers.[2] Depending on the concentration of these additives, DNA exhibits a folded or unfolded conformation. Nevertheless, with all these strategies, it is impossible to act in a reversible way on the DNA higher-order structure under a constant chemical composition.Moreover, for transfection applications, compacting DNA is an essential step to allow the entry of DNA into the cell. In most cases, however, DNA remains in a compact conformation inside the cell, which can significantly alter the DNA gene expression. Using an external stimulus to control DNA higherorder structure within a cell-sized compartment has thus became an important challenge.On the other hand, motivated by the perspective of DNA vectorization, [3] preparation of artificial cells [4] or biochemical microreactors, [5] many scientists have attempted to encapsulate DNA into cell-like microcompartments, for example, cellsized liposomes [6] or phospholipid-coated microdroplets. [7] Consequently, various successful strategies have been proposed to prepare DNA-liposome complexes [8] or encapsulate DNA inside liposomes.[9] In most cases encapsulated DNA molecules were typically smaller than a few thousands base pairs. However, in nature, genomic DNA molecules can be much larger, up to hundreds of kbp (kilo base pairs). To the best of our knowledge, no method has been proposed to encapsulate efficiently, in a controlled way, and without degradation, DNA molecules that are larger than 1 kbp into cell-sized liposomes. One paper reported the encapsulation of T4 DNA molecules, but the data were not sufficient to draw conclusions about the integrity of encapsulated DNA chains.[10] Another strategy was to encapsulate DNA in a compact state, but DNA molecules remained in their compact state once they were encapsulated. [11] Very recently, Le Ny and Lee made a breakthrough by proposing a system where DNA higher-structure can be controlled by light in a reversible manner. [12] This was achieved by adding to a DNA solution a photosensitive cationic surfactant, azobenzene trimethylammonium bromide surfactant (AzoTAB). The apolar tail of the surfactant contains an azo group, which is mainly in the trans (more hydrophobic) conformation under visible conditions. Under UV illumination (365 nm), the azo group photoisomerizes into the cis (more hydrophilic) conformation. They demonstrated that there exists an AzoTAB concentration range for which DNA is in the compact state under dark/visible conditions but in the unfolded state under UV illumination, that is, DNA higher-orde...

PIPT from the Beginning to Future

“…Even if a number of general considerations discussed here can be also applied to these situations, it is useful to refer the reader to recent reviews on the light manipulation of magnetic order [75] or soft and biochemical matter [34]. Another kind of cooperative photoinduced phenomena, not discussed here, concerns the photostationary macroscopic state originating from the quantum condensation of electron-hole-photon systems [76].…”

“…In the first case, under continuous photoirradiation, some systems, such as spin crossover [31], cyano--bridged metal [32], metal oxide [33] and even biochemical ones [34], may exhibit light driven bistability between two macroscopic states. A general universal frame exists within the physics of nonlinear dynamics and bifurcations [35].…”

Light and host–guest inclusion mediated salmon sperm DNA/surfactant interactions

“…Lynn and Abbott reported the reversible condensation of DNA using a redox-active surfactant [39]. Compared with the other external stimuli to trigger DNA decompaction and release, light input is considered to be advantageous benefitting from its capability of remote control [40][41][42]. For example, Lee developed a means to control DNA compaction and gene delivery by light input in cationic or cationic-anionic surfactant system [43,44].…”

Sequence-independent and reversible photocontrol of transcription/expression systems using a photosensitive nucleic acid binder

“…AzoTAB is a cationic surfactant which apolar tail undergoes a trans to cis isomerization at 365 nm. Consequently, there exists an AzoTAB concentration range for which genomic DNA is compacted under dark conditions but unfolded under UV illumination at 365 nm (11,12). This can be interpreted as a stronger DNA binding affinity of the trans form due to its more hydrophobic apolar tail.…”