Resolution of R-loops by INO80 promotes DNA replication and maintains cancer cell proliferation and viability.

Collisions between the DNA replication machinery and co-transcriptional R-loops can impede DNA synthesis and are a major source of genomic instability in cancer cells. How cancer cells deal with R-loops to proliferate is poorly understood. Here we show that the ATP-dependent chromatin remodelling INO80 complex promotes resolution of R-loops to prevent replication-associated DNA damage in cancer cells. Depletion of INO80 in prostate cancer PC3 cells leads to increased R-loops. Overexpression of the RNA:DNA endonuclease RNAse H1 rescues the DNA synthesis defects and suppresses DNA damage caused by INO80 depletion. R-loops co-localize with and promote recruitment of INO80 to chromatin. Artificial tethering of INO80 to a LacO locus enabled turnover of R-loops in cis. Finally, counteracting R-loops by INO80 promotes proliferation and averts DNA damage-induced death in cancer cells. Our work suggests that INO80-dependent resolution of R-loops promotes DNA replication in the presence of transcription, thus enabling unlimited proliferation in cancers.

Telomerase Activity and Telomere Length in Human Benign Prostatic Hyperplasia Stem-like Cells and Their Progeny Implies the Existence of Distinct Basal and Luminal Cell Lineages.

UNLABELLED: Benign prostatic hyperplasia (BPH) treatments have changed little over many years and do not directly address the underlying cause. Because BPH is characterised by uncontrolled cell growth, the chromosomal telomeres should be eroded in the reported absence or low levels of telomerase activity, but this is not observed. We investigated the telomere biology of cell subpopulations from BPH patients undergoing transurethral resection of prostate (TURP). Measurement of TERC, TERT, and telomerase activity revealed that only the epithelial stem-like and progenitor fractions expressed high levels of telomerase activity (p<0.01) and individual enzyme components (p<0.01). Telomerase activity and TERT expression were not detected in stromal cells. Telomere length measurements reflected this activity, although the average telomere length of (telomerase-negative) luminal cells was equivalent to that of telomerase-expressing stem/progenitor cells. Immunohistochemical analysis of patient-derived BPH arrays identified distinct areas of luminal hyperproliferation, basal hyperproliferation, and basal-luminal hyperproliferation, suggesting that basal and luminal cells can proliferate independently of each other. We propose a separate lineage for the luminal and basal cell components in BPH. PATIENT SUMMARY: We unexpectedly found an enzyme called telomerase in the cells that maintain benign prostatic hyperplasia (BPH), suggesting that telomerase inhibitors could be used to alleviate BPH symptoms.