DNA compaction: fundamentals and applications
Compaction is the process in which a large DNA molecule undergoes a transition between an elongated conformation and a very compact form. In nature, DNA compaction occurs to package genomic material inside tiny spaces such as viral capsids and cell nuclei. In vitro, several strategies exist to compact DNA. In this review, we first provide a physico-chemical description of this phenomenon, focusing on the modes of compaction, the types of compaction agents and the chemical and physical parameters that control compaction and its reverse process, decompaction. We then describe three main kinds of applications. First, we show how regulated compaction/decompaction can be used to control gene activity in vitro, with a particular emphasis on the use of light to reversibly control gene expression. Second, we describe several approaches where compaction is used as a way to reversibly protect DNA against chemical, biochemical, or mechanical stresses. Third, we show that compact DNA can be used as a nanostructure template to generate nanomaterials with a well-defined size and shape. We conclude by proposing some perspectives for future biochemical and biotechnological applications and enumerate some remaining challenges that we think worth being undertaken.