Nature is full of parasites — organisms that flourish and proliferate at the expense of another species. Surprisingly, these same competing roles of parasite and host can be found in the microscopic molecular world of the cell. A new study by two Illinois researchers has demonstrated that dynamic elements within the human genome interact with each other in a way that strongly resembles the patterns seen in populations of predators and prey.
Goldenfeld and Xue embarked on this work because of their interest in transposons, small regions of DNA that can move themselves from one part of the genome to another during the lifetime of a cell — a capability that has earned them the name “jumping genes.” Collectively, various types of transposons make up almost half of the human genome. When they move around, they may create mutations in or alter the activity of a functional gene; transposons can therefore create new genetic profiles in a population for natural selection to act on, in either a positive or negative way.
The Illinois researchers wanted to learn more about how evolution works on this level, the level of whole organisms, by looking at the metaphorical ecosystem of the human genome. In this view, the physical structure of the DNA that makes up the genome acts like an environment, in which two types of transposons, long interspersed nuclear elements (LINEs) and short interspersed nuclear elements (SINEs), have a competitive relationship with one another. In order to replicate, SINEs steal the molecular machinery that LINEs use to copy themselves, somewhat like a cuckoo bird tricks other birds into raising her chicks for her while abandoning their own.
Goldenfeld’s model made the surprising prediction that these oscillations occur over a timescale that is longer than the human lifespan — waves of Alu elements and L1 elements pushing and pulling at each other in slow motion across generations of the human genomes that carry them. Paper. (paywall) – Chi Xue, Nigel Goldenfeld. Stochastic Predator-Prey Dynamics of Transposons in the Human Genome. Physical Review Letters, 2016; 117 (20) DOI: 10.1103/PhysRevLett.117.208101
Somehow parasitism does not seem to describe this remarkable system adequately because parasites do not work for the good of their host. But the researchers probably have to describe the relationship that way for Darwinian reasons.
See also: Researchers: Jumping genes make the Tree of Life a bush
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