10779/crick.11619840.v1 Diana Zatreanu Diana Zatreanu Zhong Han Zhong Han Richard Mitter Richard Mitter Emanuela Tumini Emanuela Tumini Hannah Williams Hannah Williams Lea Gregersen Lea Gregersen A Barbara Dirac-Svejstrup A Barbara Dirac-Svejstrup Stefania Roma Stefania Roma Aengus Stewart Aengus Stewart Andres Aguilera Andres Aguilera Jesper Q Svejstrup Jesper Q Svejstrup Elongation factor TFIIS prevents transcription stress and R-loop accumulation to maintain genome stability The Francis Crick Institute 2020 53BP1 DNA-RNA hybrids R-loops RNA polymerase II TFIIS backtracking transcript cleavage transcript elongation transcription-associated genome instability Svejstrup FC001166 AS-ack PRT-ack HTS-ack CB Developmental Biology 06 Biological Sciences 11 Medical and Health Sciences 2020-01-15 16:53:55 Journal contribution https://crick.figshare.com/articles/journal_contribution/Elongation_factor_TFIIS_prevents_transcription_stress_and_R-loop_accumulation_to_maintain_genome_stability/11619840 Although correlations between RNA polymerase II (RNAPII) transcription stress, R-loops, and genome instability have been established, the mechanisms underlying these connections remain poorly understood. Here, we used a mutant version of the transcription elongation factor TFIIS (TFIISmut), aiming to specifically induce increased levels of RNAPII pausing, arrest, and/or backtracking in human cells. Indeed, TFIISmut expression results in slower elongation rates, relative depletion of polymerases from the end of genes, and increased levels of stopped RNAPII; it affects mRNA splicing and termination as well. Remarkably, TFIISmut expression also dramatically increases R-loops, which may form at the anterior end of backtracked RNAPII and trigger genome instability, including DNA strand breaks. These results shed light on the relationship between transcription stress and R-loops and suggest that different classes of R-loops may exist, potentially with distinct consequences for genome stability.