Aging-declined RNA Exportation Impairs Hematopoietic Stem Cells by Inducing R-Loop

It is well acknowledged that aging-induced DNA damage accumulation impairs hematopoietic stem cell (HSC). While, how DNA damage is accumulated and how to eliminate it to rejuvenate aged HSCs are largely unknown. In this study, we observed that RNA exportation is compromised in aged HSCs due to aging-declined Alyref, the main component of TREX (transcription/export) complex. Targeted dysfunction of Alyref leads to RNA lingering in the nucleus and recapitulates the function of aged HSCs. Mechanistically, RNA accumulation in nucleus results in the formation of RNA:DNA hybrids, called R-loop structures, and subsequent induction of replication stress. Genome-wide profiling reveals significant increase of R-Loop in aged HSCs, which is significantly associated with resident RNA in the nucleus. Quantitative refill of Alyref in aged HSCs significantly restores RNA shuttling, dampens R-Loop and replication stress, and ultimately ameliorates the function of aged HSCs. In brief, our study for the first time demonstrates that aging-induced replication stress originates from the formation of aberrant RNA shuttling-driven R-loop structures and raises the possibility that quantitatively manipulating Alyref signaling can counter the physiologically deleterious effect of aging on HSCs. Overall design: To systemically examine the correlation of R-Loop with HSC aging, we profiled the R-Loop between young and aged HSCs; freshly isolated HSCs ( Lineage-ckit+Sca1+CD34-) were subjected for ssDRIP-seq; profiling the genome-wide R-Loop at single-nucleotide resolution in young and aged HSCs to identify the exact region wherein R-Loop is strengthened upon aging