A histone-like protein induces plasmid DNA to form liquid crystals in vitro and gene compaction in vivo

• Published in: International journal of molecular sciences 2013-12, Vol.14 (12), p.23842-23857
• Main Authors: Sun, Shiyong, Liu, Mingxue, Dong, Faqin, Fan, Shenglan, Yao, Yanchen
• Format: Article
• Language: English
• Subjects: Chromosomes; Circular Dichroism; Crystals; Dinoflagellida - metabolism; Escherichia coli - metabolism; gene condensation; Gene Transfer Techniques; Genetic engineering; histone-like protein; Histones - chemistry; Histones - genetics; Histones - metabolism; liquid crystal; Liquid Crystals - chemistry; Microorganisms; Microscopy; Microscopy, Atomic Force; non-viral gene delivery; Phase transitions; plasmid; Plasmids - chemistry; Plasmids - metabolism; Polyethylene glycol; Polymers; Protein Binding; Proteins; Protozoan Proteins - chemistry; Protozoan Proteins - genetics; Protozoan Proteins - metabolism; Recombinant Proteins - biosynthesis; Recombinant Proteins - chemistry; Recombinant Proteins - genetics
• ISSN: 1422-0067; 1661-6596; 1422-0067
• DOI: 10.3390/ijms141223842

The liquid crystalline state is a universal phenomenon involving the formation of an ordered structure via a self-assembly process that has attracted attention from numerous scientists. In this study, the dinoflagellate histone-like protein HCcp3 is shown to induce super-coiled pUC18 plasmid DNA to enter a liquid crystalline state in vitro, and the role of HCcp3 in gene condensation in vivo is also presented. The plasmid DNA (pDNA)-HCcp3 complex formed birefringent spherical particles with a semi-crystalline selected area electronic diffraction (SAED) pattern. Circular dichroism (CD) titrations of pDNA and HCcp3 were performed. Without HCcp3, pUC18 showed the characteristic B conformation. As the HCcp3 concentration increased, the 273 nm band sharply shifted to 282 nm. When the HCcp3 concentration became high, the base pair (bp)/dimer ratio fell below 42/1, and the CD spectra of the pDNA-HCcp3 complexes became similar to that of dehydrated A-form DNA. Microscopy results showed that HCcp3 compacted the super-coiled gene into a condensed state and that inclusion bodies were formed. Our results indicated that HCcp3 has significant roles in gene condensation both in vitro and in histone-less eukaryotes in vivo. The present study indicates that HCcp3 has great potential for applications in non-viral gene delivery systems, where HCcp3 may compact genetic material to form liquid crystals.