Two 2023 papers on endogenous retroviruses (ERVs) and aging relationships, starting with the Introduction section of a comprehensive study:

“Several causal determinants of aging-related molecular changes have been identified, such as epigenetic alterations and stimulation of senescence-associated secretory phenotype (SASP) factors. Although the majority of these studies describe aging determinants originating primarily from protein-coding genes, the non-coding part of the genome has started to garner attention as well.

ERVs belonging to long terminal repeat (LTR) retrotransposons are a relic of ancient retroviral infection, fixed in the genome during evolution, comprising about 8% of the human genome. As a result of evolutionary pressure, most human ERVs (HERVs) accumulate mutations and deletions that prevent their replication and transposition function. However, some evolutionarily young subfamilies of HERV proviruses, such as the recently integrated HERVK, maintain open reading frames encoding proteins required for viral particle formation.

In this study, using cross-species models and multiple techniques, we revealed an uncharacterized role of endogenous retrovirus resurrection as a biomarker and driver for aging. Specifically, we identified endogenous retrovirus expression associated with cellular and tissue aging and that the accumulation of HERVK retrovirus-like particles (RVLPs) mediates the aging-promoting effects in recipient cells. More importantly, we can inhibit endogenous retrovirus-mediated pro-senescence effects to alleviate cellular senescence and tissue degeneration in vivo, suggesting possibilities for developing therapeutic strategies to treat aging-related disorders.”

https://www.cell.com/cell/fulltext/S0092-8674(22)01530-6 “Resurrection of endogenous retroviruses during aging reinforces senescence”

This first paper’s foreword summarized their many experiments and findings:

“The study found that HERVK transcripts, viral proteins, and RVLPs were highly activated in prematurely aged human mesenchymal progenitor cells (hPMCs). This was similarly observed in aged human primary fibroblasts and hPMCs. They also discovered that decreasing silencing epigenetic marks DNA methylation and H3K9me3 while increasing H3K36me3 enabled HERVK expression.

These observations also raise several intriguing questions:

• HERVK is occasionally activated and eventually suppressed under physiological conditions, for example, in human embryonic cells. It would be fascinating to probe the possibility of mimicking physiological conditions in order to turn off the positive feedback between HERVK and senescence.
• ERVs are hallmarks of aging in different species, including human, primate, and mouse. Future quantification of the absolute physiological level of ERVs across a broad population of various ages might provide further insights into the relationship between ERVs and organismal age.”

https://academic.oup.com/lifemedi/advance-article/doi/10.1093/lifemedi/lnad001/6982772 “Endogenous retroviruses make aging go viral”

Previously curated papers on these subjects include:

A study of our evolutionary remnants

“Repressive epigenetic marks associated with ERVs, particularly LTRs, show a remarkable switch in silencing mechanisms, depending on evolutionary age:

• Young LTRs tend to be CpG-rich and are mainly suppressed by DNA methylation, whereas
• Intermediate age LTRs are associated predominantly with histone modifications, particularly histone H3 lysine 9 (H3K9) methylation.
• Evolutionarily old LTRs are more likely inactivated by accumulation of loss-of-function genetic mutations.”

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