DNA-protein interactions involved in single strand DNA-break repair

LUIS MARIANO POLO

Congreso; Reunión conjunta SAIB SAMIGE 2020; 2020

DNA breaks are a potentially dangerous form of DNA damage that could lead to cell death or cancer. ADP-ribosylation (ADPr) is a post-translational modification that signals DNA damage sites on chromatin. In mammals, this reaction is performed by specialised members of the PARP ?poly-(ADP-ribose) polymerase? family of enzymes, which are activated by a range of DNA strand distortions, such as nicks and breaks. By using NMR, biochemistry, biophysics and cell biology, I have studied two different proteins involved in the ADPr signalling of single strand DNA-break (SSB) repair, PARP3 and XRCC1.PARP3 is the most recently characterised member of the PARP family, which is expected to be involved in a later stage of SSB repair than XRCC1. PARP3 contains two highly conserved domains ?WGR (Trp-Gly-Arg) and catalytic? connected by a short linker. I will show that PARP3 employs a conserved DNA binding interface within the WGR domain to detect the DNA damage; and that in the absence of DNA, the two domains of PARP3 behave as independent entities that get rigidified and coalesced upon DNA interaction.XRCC1 is a protein containing three domains that mediate interactions with multiple components of the single-strand break repair system. By recognising poly-ADPr signal (the product of PARP1 and PARP2 activity), XRCC1 is recruited to the damage site, where it acts as a hub for Polβ, LigIIIα and end-processing factors, like APTX and APLF. The central XRCC1- BRCT domain was described previously as the poly-ADPr binding domain. Now, I have identified and characterised new functions for this domain that will help to understand its biological relevance.