RNAPII response to transcription-blocking DNA lesions in mammalian cells.

RNA polymerase II moves along genes to decode genetic information stored in the mammalian genome into messenger RNA and different forms of non-coding RNA. However, the transcription process is frequently challenged by DNA lesions caused by exogenous and endogenous insults, among which helix-distorting DNA lesions and double-stranded DNA breaks are particularly harmful for cell survival. In response to such DNA damage, RNA polymerase II transcription is regulated both locally and globally by multi-layer mechanisms, whereas transcription-blocking lesions are repaired before transcription can recover. Failure in DNA damage repair will cause genome instability and cell death. Although recent studies have expanded our understanding of RNA polymerase II regulation confronting DNA lesions, it is still not always clear what the direct contribution of RNA polymerase II is in the DNA damage repair processes. In this review, we focus on how RNA polymerase II and transcription are both repressed by transcription stalling lesions such as DNA-adducts and double strand breaks, as well as how they are actively regulated to support the cellular response to DNA damage and favour the repair of lesions.

Persistence of RNA transcription during DNA replication delays duplication of transcription start sites until G2/M.

As transcription and replication use DNA as substrate, conflicts between transcription and replication can occur, leading to genome instability with direct consequences for human health. To determine how the two processes are coordinated throughout S phase, we characterize both processes together at high resolution. We find that transcription occurs during DNA replication, with transcription start sites (TSSs) not fully replicated along with surrounding regions and remaining under-replicated until late in the cell cycle. TSSs undergo completion of DNA replication specifically when cells enter mitosis, when RNA polymerase II is removed. Intriguingly, G2/M DNA synthesis occurs at high frequency in unperturbed cell culture, but it is not associated with increased DNA damage and is fundamentally separated from mitotic DNA synthesis. TSSs duplicated in G2/M are characterized by a series of specific features, including high levels of antisense transcription, making them difficult to duplicate during S phase.