Did the first virus self-assemble from self-replicating prion proteins and RNA?
DNA is the molecule responsible for storing and processing genetic information today. In Earth's primeval environmental conditions, RNA was probably more suited for this function, due to its capability to act also as a catalytic enzyme. Some proteins are stable and reliable molecules even in extreme conditions, and under certain circumstances, proteins may play a role in transmitting certain phenotypes that are inherited in a non-Mendelian manner. When the dominant native state of a prion protein is replaced by a misfolded one, the resultant infective protein is associated with several neurological diseases in mammals. The misfolded proteins are remarkably resistant to even the most extreme environments. Prions are also associated with the transmission of certain fungal traits epigenetically, supporting the hypothesis that prions are a possible relic of an early stage of peptide evolution. The primitive world probably contained both self-replicating RNA molecules and prions, and prions attach easily to nucleic acids, and also fold and cause other proteins to fold in the same way. Consequently, a capsid could form from prion protein, enclosing the RNA, and perhaps creating the first RNA virus. A capsid originating from prion proteins would be a versatile and effective protection to RNA and could also explain some characteristics of virus self-assembly that are not well understood.