Lessons from three infection cycles: how unrelated viruses handle their genomes

Viruses are obligate parasites. For all their diversity in form, genome and habitat, they face one common challenge, which is how to preserve and transmit their genetic information. Fold the genome small enough to fit. Keep it intact outside the cell. Release it inside the cell.

This talk follows three viruses through infection, imaged in the cell by cryo-electron tomography. One is an archaeal virus from acidic hot springs, the other two are giant viruses infecting unicellular marine haptophyte algae.

The three are unrelated by sequence, and their hosts and habitats have little in common, yet at the point where the genome is handled the same feature keeps appearing, a nucleoprotein filament.

If filament formation is a recurrent solution rather than three unrelated coincidences, what decides when the filament winds and when it lets go? This question is still open. Anything that binds, protects and releases nucleic acids on cue is of interest well beyond virology.