Moreover, R-loop accumulation could contribute significantly to genomic instability in WS cells, as revealed by experiments performed by overexpressing an ectopic GFP-RNaseH1, a ribonuclease that specifically degrades the RNA moiety of DNA–RNA hybrids in the nucleus, or by transcription inhibition, which strongly reduced the levels of DNA damage and the frequency of chromosomal aberrations in WS cells. This evidence concerns the gene RNASEH1 and Werner syndrome.