Regulation of topoisomerase I–induced mutagenesis and its impact on aging in yeast

Abstract

Aging is characterized by several molecular hallmarks, including accumulation of mutations in the genome. Given the interconnected nature of these hallmarks of aging, it is challenging to distinguish causative factors from their consequences. However, genomic instability is a strong candidate as a driver of aging due to its role in accumulating cellular damage over time, ultimately compromising genome integrity and cellular function. One of the most frequent forms of DNA damage is the incorporation of ribonucleotides (rNMPs) into the genome, which can lead to mutations and genome instability, making rNMP processing an intriguing candidate for influencing aging. Here, we investigate the role of Topoisomerase I (Top1) in rNMP repair and its impact on genomic integrity and aging. We find that Top1-mediated DNA damage is elevated in aged yeast cells compared to their younger counterparts, suggesting an age-associated increase in Top1 activity or its mutagenic consequences. Furthermore, processes known to extend lifespan, such as caloric restriction, reduce Top1-dependent mutation accumulation, reinforcing the link between genome stability and aging. While rNMP processing does not appear to influence yeast lifespan under normal conditions, we demonstrate that loss of RNase H2 activity shortens lifespan in worms, and that subsequent degradation of Top1 in adult worms rescues lifespan to wildtype levels. These findings support a model in which Top1 activity at rNMPs contributes to genomic instability and may act as a pro-aging factor, especially under conditions where rNMP removal is impaired.

Together, this work highlights a mechanistic connection between genome maintenance pathways and aging, advancing our understanding of how genomic instability shapes lifespan.