A recent study led by biologists from Indian University and Montana State University has found a connection between viruses that infect eukaryotes and viruses that infect archaea growing in volcanic springs (article). Viruses like HIV and Ebola that infect eukaryotic cells and the virus Sulfolobus turreted icosahedral virus (STIV) that infects Sulfolobus sofataricus, an archaea found in volcanic springs, share a common feature; they both must hijack the same set of proteins found in their hosts' cells to be able to complete their life cycles.
The set of proteins hijacked by viruses in both eukaryotes and archea is the machinery known as the Endosomal Sorting Complexes Required for Transport (ESCRT). In the host cell, ESCRT is a set of proteins used for biological functions involving membrane remodeling. It has also been found to play a key role in the cell division of eukaryotes and archaea. Viruses in both eukaryotes and archea have developed a way to use the ESCRT to their own advantage. In this study, researchers looked specifically at STIV and its dependency on its host's (Sulfolobus solfataricus) ESCRT. They looked for an interaction between STIV and ESCRT using two-hybrid screening. This type of hybrid screening identifies binding interactions between two proteins or between a DNA molecule and a protein. Researchers uncovered two examples where viral proteins interacted with ESCRT proteins in STIV-infected Sulfolobus solfataricus. They were able to conclude that the virus is able to recruit the ESCRT machinery to aid in its own assembly and then later to help it open up the seven-sided pyramid structure that makes up the membrane of its host cell in Sulfolobus solfataricus. Once the membrane of its host cell is opened up, the virus can release its progeny and wreak havoc on other host cells. The same ESCRT machinery hijacked by STIV is also recruited by HIV in eukaryotic cells to aid in HIV's viral budding. This research has led to the hypothesis that due to the two billion year time difference between the existence of the first archaea and the existence of the first eukaryotes, viruses have been hijacking ESCRT for their own benefit from before the time when archaea and eukayotes branched off into different domains.