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 HSC remain largely obscure. This study uncovers a notable surge in R-Loop presence within aged HSC, notably co-localized with γH2AX and replication protein A (RPA), and correlated with RNA residency in the nucleus. Targeted induction of R-Loop impairs the function of HSC. Mechanistically, RNA exportation is compromised in aged HSC due to a decline in Alyref, the primary constituent of the transcription- export complex (TREX). Specifically, Alyref dysfunction results in RNA retention within the nucleus, mimicking the functional characteristics of aged HSC. 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 HSC notably reinstates RNA transportation, diminishes R-Loop formation and replication stress, and ultimately enhances the performance of aged HSC. 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 HSC.