RTEL Resolves G4/R-Loops to Avert Replication-Transcription Collisions

RTEL1 is an essential helicase that maintains telomere integrity and facilitates DNA replication. The source of replication stress in Rtel1 deficient cells remains unclear. Here, we report that loss of RTEL1 confers extensive transcriptional changes independent of its roles at telomeres. The majority of affected genes in Rtel1-/- cells possess G4-DNA forming sequences in their promoters and are similarly altered at a transcriptional level in wild-type cells treated with the G4-DNA stabilizer TMPyP4. Failure to resolve G4-DNAs formed in the displaced strand of RNA-DNA hybrids in Rtel1-/- cells is suggested by increased R-loops and elevated transcription-replication collisions (TRCs). Moreover, removal of R-loops by RNaseH1 overexpression suppresses TRCs and alleviates the global replication defects observed in Rtel1-/-, Rtel1PIP_box knock-in cells and in wild type cells treated with TMPyP4. We propose that RTEL1 unwinds G4-DNA/R-loops to avert TRCs, which is important to prevent global deregulation in both transcription and DNA replication.