RNA-dependent DNA damage response

Thesis

DNA double-strand breaks (DSBs) are the most lethal form of DNA damage, and they require a delicate coordination between transcriptional activity and repression for effective repair. Long nascent transcripts produced near DSBs can be processed into small non-coding RNAs, called DDRNA or diRNA in DICER and DROSHA-dependent manner, which aid in recruiting DNA damage response (DDR) factors. Additionally, these transcripts can form DNA: RNA hybrids and R-loop structures when they bind to their template DNA. These structures accumulate near DSBs and enhance the DDR process, but their precise functions and the mechanisms governing transcription around DSBs remain elusive.

Furthermore, transcriptional repression near DSBs is essential for DDR, creating a complex interplay between transcriptional activation at DSBs and repression nearby, which is regulated by the chromatin landscape. How is chromatin landscape modulated remains poorly understood.

In Chapters 3 and 4 of my study, I demonstrate that the GATAD2B-NuRD complex associates with DSBs in a transcription and R-loop-dependent manner. This interaction leads to a chromatin boundary formation, promoting histone deacetylation and chromatin condensation around DSBs. The presence of this complex near damaged genomic regions is crucial for silencing of gene expression on the same DNA strand. In the absence of the GATAD2B-NuRD complex, chromatin relaxes excessively, and DNA end resection is extended, resulting in the failure of homologous recombination (HR) repair.

In Chapter 5 of my thesis, I investigate the role of DROSHA in regulating transcription around DSBs. I propose that DROSHA positively influences DSB-induced transcription by releasing paused RNA Pol II from DSB ends. Depletion of DROSHA leads to RNA Pol II stalling near DSBs, with the interaction between CBP80 and DROSHA potentially playing a crucial role.

In summary, my findings highlight the GATAD2B-NuRD complex as a coordinator in the intricate interplay between transcription and the chromatin landscape. Additionally, I emphasize DROSHA's significance as a regulator of DSB-induced transcription within the RNA-dependent DNA damage response.

Authors: Liu, Z

• DOI: 10.5287/ora-0zjpergvp
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English
• Keywords: NuRD complex; DNA damage response; DNA: RNA hybrids