Aging-declined RNA exportation impairs hematopoietic stem cells by inducing R-loop

Aging-related accumulation of DNA damage adversely affects hematopoietic stem cell (HSC). However, the mechanisms underlying this accumulation and strategies for its elimination to rejuvenate aged HSCs remain largely obscure. This study uncovers a notable surge in R-Loop presence within aged HSCs, notably co-localized with γH2AX and RPA (Replication Protein A), and correlated with RNA residency in the nucleus. Targeted induction of R-Loop impairs the function of HSCs. Mechanistically, RNA exportation is compromised in aged HSCs due to a decline in Alyref, the primary constituent of the TREX (transcription-export complex). Specifically, Alyref dysfunction results in RNA retention within the nucleus, mimicking the functional characteristics of aged HSCs. The nuclear accumulation of RNA leads to the formation of RNA:DNA hybrids, known as R-Loop structures, consequently inducing replication stress and DNA damage. Introducing a quantitative boost of Alyref in aged HSCs notably reinstates RNA transportation, diminishes R-Loop formation and replication stress, and ultimately enhances the performance of aged HSCs. Taken together, our research demonstrates the initial revelation that aging-triggered replication stress stems from abnormal RNA transportation-propelled R-Loop configurations, hinting at the potential of quantitatively modulating RNA transportation to mitigate the physiological drawbacks of aging on HSCs.