Oral Presentation 49th Lorne Conference on Protein Structure and Function 2024

The molecular details of a novel phosphorylation-dependent interaction between MRN and the SOSS complex (#10)

Serene El-Kamand 1 , Mark N Adams 2 , Jacqueline M Matthews 3 , Mar-Dean Du Plessis 1 , Ben Crossett 3 , Angela Connolly 3 , Natasha Breen 1 , Alexander Dudley 1 , Derek J Richard 2 , Roland Gamsjaeger 1 , Liza Cubeddu 1
  1. Western Sydney University, Penrith, NSW, Australia
  2. Institute of Health Biomedical Innovation, Queensland University of Technology, Brisbane, QLD, Australia
  3. University of Sydney, Sydney

The repair of double-strand DNA breaks (DSBs) by homologous recombination is crucial in the maintenance of genome integrity. While the key role of the Mre11-Rad50-Nbs1 (MRN) complex in repair is well known, hSSB1 (SOSSB and OBFC2B), one of the main components of the sensor of single-stranded DNA (SOSS) protein complex, has also been shown to rapidly localize to DSB breaks and promote repair. We have previously demonstrated that hSSB1 binds directly to Nbs1, a component of the MRN complex, in a DNA damage-independent manner. However, recruitment of the MRN complex has also been demonstrated by an interaction between Integrator Complex Subunit 3 (INTS3; also known as SOSSA), another member of the SOSS complex, and Nbs1. In this study, we utilize a combined approach of in silico, biochemical, and functional experiments to uncover the molecular details of INTS3 binding to Nbs1. We demonstrate that the forkhead-associated domain of Nbs1 interacts with INTS3 via phosphorylation-dependent binding to INTS3 at Threonine 592, with contributions from Serine 590. Based on these data, we propose a model of MRN recruitment to a DSB via INTS3.