Ageing-dependent ribosome pausing and nascent polypeptide aggregation
Increased protein misfolding and aggregation are key hallmarks of ageing and many age-related diseases. As generating and maintaining a functional proteome (proteostasis) is crucial to every cellular process, this age-related decline in proteostasis is suggested to play a primary role in the breakdown of diverse cellular subsystems during ageing. Indeed, augmented proteostasis pathways are associated with extended lifespan across different species. With the ribosome as the earliest proteostasis checkpoint, decreased protein synthesis is also a conserved mechanism that extends lifespan. Yet, it remains unclear whether ageing impacts translation after initiation. Here, we use worms and yeast to investigate how ageing influences translation elongation. We show an age-dependent increase in ribosome pausing at diverse positions in coding sequences. This pausing is conserved in both worms and yeast, particularly at Arg and polybasic regions. We further show that such pausing is associated with the age-dependent aggregation of truncated nascent proteins involved in proteostasis pathways, notably aminoacyl tRNA synthetases. Moreover, we find that impairment in clearing truncated nascent proteins is associated with decreased lifespan. These data establish elongation kinetics and co-translational quality control as critical contributors of the age-related proteostasis collapse, which may precipitate the systemic decline observed during ageing. Overall design: Replicate ribosome profiling libraries were prepared during ageing of worms and yeast, including the long-lived sch9? yeast strain.