Olivetol induces a non-genotoxic nucleolar DNA damage response via membrane-dependent stress signaling.

Olivetol (5-pentylresorcinol) is a naturally occurring alkylresorcinol whose cellular mechanism remains poorly understood. Here, we show that olivetol induces a non-genotoxic nucleolar DNA damage response (n-DDR) in human cells. Although moderately cytotoxic, olivetol did not cause detectable genomic DNA double-strand breaks. Instead, it triggered γH2AX accumulation at ribosomal DNA (rDNA), recruitment of TOPBP1 to Treacle, nucleolar disorganization, and repression of ribosomal RNA synthesis. Mechanistically, olivetol closely phenocopied hypotonic stress, inducing a rapid and reversible n-DDR associated with antisense RNA polymerase II transcription within the rRNA coding region and accumulation of R-loops, consistent with transcriptional interference between RNA polymerases I and II. Both olivetol and hypotonic stress also produced shared membrane-associated phenotypes, including reduced membrane lipid order, calcium redistribution, and plasma membrane blebbing. Importantly, this non-genotoxic nucleolar response depended on cholesterol-sensitive plasma membrane organization.