Gene Evolution Accelerated by Head-On Collisions Between DNA-Code Reading Machineries

by Kathy Jones on Mar 31 2013 9:17 PM

 Gene Evolution Accelerated by Head-On Collisions Between DNA-Code Reading Machineries
Research indicates that bacteria speed up their evolution by positioning specific genes along the route in DNA encoding.
Certain genes are in prime collision paths for the moving molecular machineries that read the DNA code, as University of Washington scientists explain in this week's edition of Nature.

The spatial-organization tactics their model organism, Bacillus subtilis, takes to evolve and adapt might be imitated in other related Gram-positive bacteria, including harmful, ever-changing germs like staph, strep, and listeria, to strengthen their virulence or cause persistent infections. The researchers think that these mechanisms for accelerating evolution may be found in other living creatures as well.

Replication – the duplicating of the genetic code to create a new set of genes– and transcription – the copying of DNA code to produce a protein – are not separated by time or space in bacteria. Therefore, clashes between these machineries are inevitable. Replication traveling rapidly along a DNA strand can be stalled by a head-on encounter or same-direction brush with slower-moving transcription.

The senior authors of the study, Houra Merrikh, UW assistant professor of microbiology, and Evgeni Sokurenko, UW professor of microbiology, and their research teams are collaborating to understand the evolutionary consequences of these conflicts. The major focus of Merrikh and her research team is on understanding mechanistic and physiological aspects of conflicts in living cells – including why and how these collisions lead to mutations.

Impediments to replication, they noted, can cause instability within the genome, such as chromosome deletions or rearrangements, or incomplete separation of genetic material during cell division. When dangerous collisions take place, bacteria sometimes employ methods to repair, and then restart, the paused DNA replication, Merrikh discovered in her earlier work at the Massachusetts Institute of Technology.