DNA double helices recognize mutual sequence homology in a protein free environment.
The structure and biological function of the DNA double helix are based on interactions recognizing sequence complementarity between two single strands of DNA. A single DNA strand can also recognize the double helix sequence by binding in its groove and forming a triplex. We now find that sequence recognition occurs between intact DNA duplexes without any single-stranded elements as well. We have imaged a mixture of two fluorescently tagged, double helical DNA molecules that have identical nucleotide composition and length (50% GC; 294 base pairs) but different sequences. In electrolytic solution at minor osmotic stress, these DNAs form discrete liquid-crystalline aggregates (spherulites). We have observed spontaneous segregation of the two kinds of DNA within each spherulite, which reveals that nucleotide sequence recognition occurs between double helices separated by water in the absence of proteins, consistent with our earlier theoretical hypothesis. We thus report experimental evidence and discuss possible mechanisms for the recognition of homologous DNAs from a distance.
Baldwin
Geoff S
GS
Division of Molecular Biosciences, Department of Chemistry, Imperial College London, SW7 2AZ London, UK. g.baldwin@imperial.ac.uk
Brooks
Nicholas J
NJ
Robson
Rebecca E
RE
Wynveen
Aaron
A
Goldar
Arach
A
Leikin
Sergey
S
Seddon
John M
JM
Kornyshev
Alexei A
AA
D001482:Base Composition; D004247:DNA / Q000737:chemistry* / Q000235:genetics*; D011506:Proteins; D012689:Sequence Homology, Nucleic Acid
D011506:Proteins; D004247:DNA