Höfundar:
Karen Kristjánsdóttir, Þorkell Guðjónsson, Stefán Sigurðsson
DNA double-strand breaks (DSB) are the most cytotoxic form of DNA damage. Failure in repairing DSB has the potential to cause severe genome instability and mutations in key members of the DNA-DSB repair pathways predisposes to several type of cancer. The ability to detect and correctly repair DNA-DSB is vital for cell survival and to maintain genomic stability. Here we show that ALKBH3 and FTO, members of the alkylation-repair family, play an important role in DNA-DSB repair by regulating RNF168, crucial DNA-DSB repair regulator.
Our data revealed the presence of methylation marks on the RNF168-transcript and that ALKBH3 and FTO remove these methylation marks for efficient RNF168-mRNA export and normal RNF168-protein expression (Epitranscriptomic regulation).
CRISPR/Cas9 cell models and siRNA treatment demonstrated defective RNF168-mRNA export which results in decreased protein expression in the absence of ALKBH3/FTO. Confocal microscopy and FACS experiments established that loss of ALKBH3/FTO translates into diminished recruitment of key genome caretakers 53BP1 and RIF1 to sites of DNA-damage and inept DNA-DSB repair. Lastly cell survival and genomic instability assays revealed cells lacking ALKBH3/FTO showed increased genome instability and impaired cell survival in response to genotoxic stress inducing agents.
Our research uncovers the role of mRNA modification in the regulation of DNA-DSB repair signalling and provides further evidence for crosstalk between two essential DNA-repair pathway, alkylation-repair and DNA-DSB repair. Lack of ALKBH3/FTO might be used as a potential marker for cancer treatment response due to both lack of alkylation repair and defective DNA-DSB repair, or as possible treatment targets.