TIRR regulates mRNA export and association with P bodies in response to DNA damage
To ensure the integrity of our genetic code, a coordinated network of signalling and repair proteins known as the DNA damage response (DDR) detects and repairs DNA insults, the most toxic being double-stranded breaks (DSBs). Tudor interacting repair regulator (TIRR) is a key factor in DSB repair, acting through its interaction with p53 binding protein 1 (53BP1). TIRR is also an RNA-binding protein, yet its role in RNA regulation during the DNA damage response remains elusive. Here we show that TIRR selectively binds to a subset of mRNAs in response to DNA damage with preference for transcripts encoding transcription factors and RNA polymerase II (RNAPII) transcription regulators. Upon DNA damage, TIRR interacts with the nuclear export protein Exportin-1 (XPO1), through its nuclear export sequence (NES). Furthermore, TIRR plays a crucial role in modulation of RNA processing bodies (P bodies/PBs). TIRR itself and TIRR-bound RNA co-localises with PBs, and TIRR depletion results in nuclear RNA retention and impaired PB formation. Finally, the role of TIRR in RNA export contributes to efficient DNA damage response. This work reveals intricate involvement of TIRR in orchestrating mRNA nuclear export and storage within PBs, emphasizing its significance in the regulation of RNA-mediated DNA damage response.