MRNIP condensates promote DNA double-strand break sensing and end resection

Abstract

The rapid recognition of DNA double-strand breaks (DSBs) by the MRE11/RAD50/NBS1 (MRN) complex is critical for the initiation of DNA damage response and DSB end resection. Here, we show that MRN complex interacting protein (MRNIP) forms liquid-like condensates to promote homologous recombination-mediated DSB repair. The intrinsically disordered region is essential for MRNIP condensate formation. Mechanically, the MRN complex is compartmentalized and concentrated into MRNIP condensates in the nucleus. After DSB formation, MRNIP condensates move to the damaged DNA rapidly to accelerate the binding of DSB by the concentrated MRN complex, therefore inducing the autophosphorylation of ATM and subsequent activation of DNA damage response signaling. Meanwhile, MRNIP condensates-enhanced MRN complex loading further promotes DSB end resection. In addition, data from xenograft models and clinical samples confirm a correlation between MRNIP and radioresistance. Together, these results reveal an important role of MRNIP phase separation in DSB response and the MRN complex-mediated DSB end resection.

MRNIP interacts with sex body chromatin to support meiotic progression, spermatogenesis, and male fertility in mice

“…Recent studies showed that MRNIP forms liquid‐like condensates to promote homologous recombination‐mediated DSB repair in somatic cells 35 . Concurrently it is hypothesized that liquid–liquid phase separation, could be the mechanism behind the nucleolus, sex body, and other membrane‐less organelle formation, and MSCI during male meiosis 72,73 .…”

“…The most recent study showed that MRNIP forms liquid‐like condensates in the somatic cell nucleus to facilitate DSB end resection and DNA DSB repair 35 . This demonstrates MRNIP association with liquid–liquid phase separation, a biophysical phenomenon enabling macromolecules to condense and create co‐existing phases 35 . The report of a Mrnip knockout mouse model has shown that male mice were subfertile and states that Mrnip is probably responsible for homologous recombination through its interaction with the MRN complex in meiosis 36 .…”

NOP53 undergoes liquid-liquid phase separation and promotes tumor radio-resistance

“…Moreover, we recently identi ed that the MRN complex interacting protein (MRNIP) condensates promoted DNA DSB sensing and end resection. High level of MRNIP in tumor cells indicated a poor response to RT, which was resulted from the enhanced DNA repair capacity [19] . In this study, we showed that NOP53 was overexpression in CRC and associated with radio-resistance and poor prognosis.…”

“…OptoIDR has been used to verify the LLPS potency of IDR; the expressed Cry2 protein is a blue lightinducible self-association protein that leads to an increase of local concentration of the fused protein and facilitates the rapid formation of liquid-like droplets upon blue light stimulation [19,27] . Time-lapse imaging revealed that NOP53-Cry2-mCherry recombinant protein formed droplets upon blue light stimulation, and the fusion between different droplets was observed at the same time (Supplementary Fig.…”

“…[16,17] . Recently, we and other groups have reported that DNA repair proteins may undergo LLPS to facilitate DSB repair [13,18,19] . For example, Silvia M L Barabino, et al reported that the multifunctional DNA/RNA-binding protein fused in sarcoma (FUS) underwent LLPS upon DNA damage and its LLPS was necessary for the initiation of DDR [20] .…”