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VIRUS TO EUKARYOTIC CELLS. "If DNA and DNA replication proteins originated in viruses, one can imagine that DNA replication mechanisms have been transferred from viruses to cells. Many protein phylogenies support the idea of ancient transfers of replicative proteins between cells and viruses." https://lnkd.in/dNTbYMw View in LinkedIn

VIRAL DNA INSERTED INTO HOST. "The replication cycle of a retrovirus entails the insertion ("integration") of a DNA copy of the viral genome into the nuclear genome of the host cell. Most retroviruses infect somatic cells, but occasional infection of germline cells (cells that produce eggs and sperm) can also occur. The retroviral proteins themselves have (sometimes) been co-opted to serve novel host functions, particularly in reproduction and development. " https://lnkd.in/dwG2wT9 View in LinkedIn

VIRAL UPPER RANGE. "Some of them (e.g., T4-phages) have reached a high level of complexity in their DNA replication machinery, and consequently encode functional analogs for all proteins involved in cellular DNA replication." https://lnkd.in/dNTbYMw View in LinkedIn

EXOTIC VIRUS PROPERTIES. "Viruses can have exotic properties: they can replicate in dead cells, repair radiation-damaged hosts, or recombine with other dead viruses and generate an intact cell. In some cases, hosts can benefit from viruses. An ancient retrovirus supported the development of the placenta in mammals." https://lnkd.in/eGaw2Kq View in LinkedIn

RANGE OF SOPHISTICATION. "Some DNA viruses replicate their genome using only replication proteins encoded by their host (with the exception of initiator proteins). However, many large DNA viruses encode also several proteins involved in the elongation step of DNA replication." https://lnkd.in/dNTbYMw View in LinkedIn

VIRAL FOSSIL RECORD IS DNA. "The genomes of many organism contain endogenous viral elements (EVEs). These DNA sequences are the remnants of ancient virus genes and genomes that ancestrally 'invaded' the host germline. For example, the genomes of most vertebrate species contain hundreds to thousands of sequences derived from ancient retroviruses." https://lnkd.in/dPyAFVt View in LinkedIn

MORE FLEXIBLE. "In contrast to cellular genomes, which are all made of double-stranded DNA, viral DNA genomes are very diverse." https://lnkd.in/dNTbYMw View in LinkedIn

ANCIENT VIRAL RESURRECTION."A 35 Mio-year-old HERV was reconstructed from several defective HERV sequences by deduction of a consensus sequence as infectious virus, designated Phoenix." https://lnkd.in/eGaw2Kq View in LinkedIn

ANCIENT INFECTIONS. "Viruses were already infecting organisms some 300 million years ago, suggests a new study on what may be the oldest date yet for the emergence of an insect-infecting virus." They are considered to have emerged before modern cells. https://lnkd.in/d-szGeg View in LinkedIn

FLU VIRUSES. "Influenza A viruses have caused pandemics in humans during the 20th century, such as ‘‘Spanish Flu’’ caused by the H1N1 virus that killed 25–50 million people worldwide in 1918, ‘‘Asian Flu’’ by the H2N2 virus that killed 1–4 million people in 1957, and ‘‘Hong Kong Flu’’ by the H3N2 virus that killed 0.75–2 million people in 1968. The H1N1 and H3N2 viruses still continue to circulate and cause annual epidemics that kill 0.25–0.5 million people worldwide." https://lnkd.in/d4eZr87 View in LinkedIn