Young, T. Z. | bioRxiv Science

bioRxiv2019

Quantitative insights into age-associated DNA-repair inefficiency in single cells

The double strand break (DSB) is a highly toxic form of DNA damage that is thought to be both a driver and consequence of age-related dysfunction. Although DSB repair is essential for a cells survival, little is known about how DSB repair mechanisms are affected by cellular age. Here we characterize the impact of cellular aging on the efficiency of single-strand annealing (SSA), a repair mechanism for DSBs occurring between direct repeats. Using a single-cell reporter of SSA repair, we measure SSA repair efficiency in young and old cells, and report a 23.4% decline in repair efficiency. This decline is not due to increased usage of non-homologous end joining (NHEJ). Instead, we identify increased G1-phase duration in old cells as a factor responsible for the decreased SSA repair efficiency. We further explore how SSA repair efficiency is affected by sequence heterology and find that heteroduplex rejection remains high in old cells. Our work provides novel quantitative insights into the links between cellular aging and DSB repair efficiency at single-cell resolution in replicatively aging cells.

systems biology↗

bioRxiv2019

Inhibition of GMP synthesis extends yeast replicative lifespan

Aging, the time-dependent accumulation of molecular damage, is the primary limiting factor of human lifespan. Slowing down damage accumulation or its prevention therefore represents a promising therapeutic paradigm to combat aging-related disease and death. While several chemical compounds extend lifespan in model organisms, their mechanism of action is often unknown, reducing their therapeutic potential. Using a systematic approach, here we show that inhibition of GMP synthesis is a novel lifespan extension mechanism in yeast. We further discover that proteasome activation extends lifespan in part through GMP insufficiency. GMP synthesis inhibition exerts its lifespan extension effect independently of the canonical nutrient-sensing and sirtuin pathways regulating lifespan. Exposing longitudinally aging yeast cells to GMP synthesis inhibition in an age-dependent manner, we demonstrate that the lifespan extension by GMP insufficiency is facilitated by slowing, rather than reversing, the aging process in cells. While GMP and its downstream metabolites are involved in many cellular processes in cells, our results rule out the combined effect of global transcription and translation on cellular lifespan. These findings elucidate the involvement of nucleotide metabolism in the aging process. The existence of clinically-approved GMP synthesis inhibitors elicits the potential of a new class of therapeutics for aging-related disorders.

systems biology↗