Preventing replication stress to maintain genome stability: resolving conflicts between replication and transcription.

DNA and RNA polymerases clash along the genome as they compete for the same DNA template. Cells have evolved specialized strategies to prevent and resolve replication and transcription interference. Here, we review the topology and architecture at sites of replication fork clashes with transcription bubbles as well as the regulatory circuits that control replication fork passage across transcribed genes. In the case of RNA polymerase II-transcribed genes, cotranscriptional processes such as mRNA maturation, splicing, and export influence the integrity of replication forks and transcribed loci. Fork passage likely contributes to reset the epigenetic landscape, influencing gene expression and transcriptional memory. When any of these processes are not properly coordinated, aberrant outcomes such as fork reversal and R-loop formation arise and trigger unscheduled recombinogenic events and genome rearrangements. The evolutionary implications of such conflicts on genome dynamics and their potential impact on oncogenic stress are discussed.