Did viruses precede other life?

Viruses share a common ancestor that existed over 3 billion years ago and may even have preceded cellular forms of life, according to a report in the May 3 PNAS by George Rice and colleagues at Montana State University.

Based on a comparison of known virus types and an icosahedral virus isolated from a hot spring in Yellowstone National Park, the team found that coat proteins in all viral types that inhabit the three domains of life—Eukarya, Bacteria, and Archaea—have conformational similarities even though the genetics underlying them is quite different.

Nearly all of the Yellowstone virus' 36 predicted open reading frame products showed no significant similarity to proteins in public databases, and so basic structural and assembly principles in this virus were compared instead, revealing an “astounding” similarity with all virus types, according to the authors.

“This suggests that this type of coat protein arrangement preceded the split of ...