Yeah, we know that somewhere between the X-games and base-jumping light beer ads, the term “Extreme” got a little played out. But, in their Perspective piece in Science, Randal Halfmann and Susan Lindquist make the case that certain proteins with unique folding properties, called prions, deserve the “extreme” label.
Prions are proteins that are stably folded in a different way than their normal siblings. Through that unique conformation, the protein’s function may be changed or inactivated altogether. And because the prion conformation acts as a template to replicate itself onto other members of the same protein, its impact can be huge.
Although prions aren’t thought of as a traditional epigenetic mechanism, the authors from the Whitehead Institute argue that maybe we ought to rethink that position. If you consider epigenetics to mean “…all mechanisms for the inheritance of biological traits that do not involve alterations to the coding sequence of DNA”, then prions certainly fit the bill; they just get the job done by altering protein folding instead of transcription or translation. Because these changes are robust, self-replicating and heritable, prions can be considered both an epigenetic process, and a way for traits to be passed from the environment to an organism (think mad cow disease).
For more background info and extreme examples of prions in action, check out the full review in Science, October 2010