A paper published in Science provides proof that viral DNA encoded in human genomes from ancient infections serves as antivirals that shield human cells against some modern viruses.

Researchers scanned the human genome using computational genomics to list any probable retroviral envelope protein-coding regions that might still have receptor binding capability. More tests were then performed to determine whether these genes were active, i.e., producing retroviral envelope gene products in particular human cell types.

After identifying antiviral envelope proteins expressed in various circumstances, the researchers concentrated on Suppressyn since it was known to bind ASCT2, the cellular entry point for a wide range of viruses known as Type D retroviruses. In the placenta and at a very early stage of human embryonic development, Suppressyn demonstrated high levels of expression.

The researchers then conducted experiments on human placental-like cells because viruses frequently target the placenta. The research demonstrates how a human protein with retroviral ancestry shuts down a cell receptor that permits viral entry and infection by a wide variety of retroviruses seen in many non-human species.

Experts also said that other envelope-derived proteins encoded in the human genome will be investigated for their potential antiviral activity. They also pointed out that ancient retroviruses integrated into the human genome offer a mechanism for defending the developing embryo against infection by related viruses.

 (Source:  https://www.sciencedaily.com/releases/2022/10/221027154145.htm)