DNA-DNA interactions in bacteriophage capsids are responsible for the observed DNA knotting.
Recent experiments showed that the linear double-stranded DNA in bacteriophage capsids is both highly knotted and neatly structured. What is the physical basis of this organization? Here we show evidence from stochastic simulation techniques that suggests that a key element is the tendency of contacting DNA strands to order, as in cholesteric liquid crystals. This interaction favors their preferential juxtaposition at a small twist angle, thus promoting an approximately nematic (and apolar) local order. The ordering effect dramatically impacts the geometry and topology of DNA inside phages. Accounting for this local potential allows us to reproduce the main experimental data on DNA organization in phages, including the cryo-EM observations and detailed features of the spectrum of DNA knots formed inside viral capsids. The DNA knots we observe are strongly delocalized and, intriguingly, this is shown not to interfere with genome ejection out of the phage.
Marenduzzo
Davide
D
Scottish Universities Physics Alliance, School of Physics, University of Edinburgh, Mayfield Road, Edinburgh EH9 3JZ, Scotland.
Orlandini
Enzo
E
Stasiak
Andrzej
A
Sumners
De Witt
de W
Tubiana
Luca
L
Micheletti
Cristian
C
D001435:Bacteriophages / Q000737:chemistry*; D055592:Biophysical Phenomena; D002213:Capsid / Q000737:chemistry*; D020285:Cryoelectron Microscopy; D042003:DNA Packaging; D004279:DNA, Viral / Q000737:chemistry*; D008958:Models, Molecular; D009010:Monte Carlo Method; D009690:Nucleic Acid Conformation; D013269:Stochastic Processes; D013816:Thermodynamics
D004279:DNA, Viral