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Bioscience: USRA Scientists Discover Prions in the Domain Archaea

March 2021

Protein-based genetic elements – prions – have long fascinated biologists because they overturn the central dogma. Far from simply causing mammalian disease, many prion-like aggregation processes produce beneficial traits. Some argued that prion-like self-assembly of proteins may have been important in the origins of life. If this would be the case, one would expect to find prions in all domains of life. Yet because archaeal prion proteins have not been identified, it has been impossible to assert that they were a generalized phenomenon throughout evolution, or perhaps were even present in our last universal common ancestor (LUCA). In the paper, evidence was provided that multiple archaeal proteins are capable of acting as prions – thus expanding our knowledge of this epigenetic phenomenon to the third and final domain of life. This adds strong support to the hypothesis that amyloid-based prions were present at the earliest stages of life’s evolution. 

This project contributes to expanding knowledge of prions to the third and final domain of life and bolstering the possibility that they were present at the time of the last universal common ancestor (LUCA). Authors: Tomasz Zajkowski, Ph.D. Research Scientist (USRA), Amanda Carbajal, NAMS intern (UC Santa Cruz), Patrick D. Brennock, NAMS intern (Stanford University), and Jessica E. Snyder, Ph.D., Research Scientist (USRA). 

Two examples of amyloid functions.
Two examples of amyloid functions. Production of amyloid provides a scaffold for bacterial extracellular matrix (top). A subtype of amyloid aggregate called prions can function as molecular switches and are inherited cytoplasmically as depicted in yeast cells (down). (Image credit Tomasz Zajkowski)


 

Micrographs of prion candidates tested, obtained using a transmission electron microscope show the typical morphology of amyloids.
Micrographs of prion candidates tested, obtained using a transmission electron microscope show the typical morphology of amyloids. (Image Credit: Zajkowski et al. 2021)

 

A phylogenomic tree of Archaea with distribution of candidate prion proteins overlain.
A phylogenomic tree of Archaea with distribution of candidate prion proteins overlain. Tips with at least 1 prion candidate are colored blue. (Image Credit: Zajkowski et al. 2021)