Regulation of DNA-End Resection by hnRNPU-like Proteins Promotes DNA Double-Strand Break Signaling and Repair

Abstract

DNA double-strand break (DSB) signaling and repair are critical for cell viability, and rely on highly coordinated pathways whose molecular organization is still incompletely understood. Here, we show that heterogeneous nuclear ribonucleoprotein U-like (hnRNPUL) proteins 1 and 2 play key roles in cellular responses to DSBs. We identify human hnRNPUL1 and -2 as binding partners for the DSB sensor complex MRE11-RAD50-NBS1 (MRN) and demonstrate that hnRNPUL1 and -2 are recruited to DNA damage in an interdependent manner that requires MRN. Moreover, we show that hnRNPUL1 and -2 stimulate DNA-end resection and promote ATR-dependent signaling and DSB repair by homologous recombination, thereby contributing to cell survival upon exposure to DSB-inducing agents. Finally, we establish that hnRNPUL1 and -2 function downstream of MRN and CtBP-interacting protein (CtIP) to promote recruitment of the BLM helicase to DNA breaks. Collectively, these results provide insights into how mammalian cells respond to DSBs.

The RNA-binding Protein Fused in Sarcoma (FUS) Functions Downstream of Poly(ADP-ribose) Polymerase (PARP) in Response to DNA Damage

“…In support of this, FUS was recently identified as a PAR-associated protein through quantitative proteomic approaches (76). The RGG domains of MRE11 as well as the RNA-processing factor hnRNPUL1 mediate recruitment to sites of DNA damage (54,75,77), suggesting that this motif may function generally as an atypical PAR binding domain. The fact that FUS targeting to DNA damage was not fully supported by RGG2 suggests that the other RGG repeats may contribute to PAR binding.…”

“…It is also possible that PAR-independent interactions contribute to the stable association of FUS with DNA damage. In the hnRNPUL1 paradigm, full recruitment required both the MRE11-RAD50-NBS1 complex and PARP-1 (54,75). We envision a similar scenario for FUS, with the low complexity PLD stabilizing FUS recruitment through heterotypic or homotypic interactions.…”

“…Although other studies have implicated a role for FUS in maintaining resistance to genotoxic stress, possibly via participation in HR repair (34,40,41), the present results indicate that FUS functions are required for optimal DSB repair through both NHEJ and HR. FUS joins a growing list of RNA-processing factors including RBMX, PPM1G, THRAP3, hnRNPUL1 and -2, and NONO, that are recruited to the proximity of DSBs and whose activities are required for genotoxin resistance and DNA repair (51)(52)(53)(54).…”

DEAD Box 1 Facilitates Removal of RNA and Homologous Recombination at DNA Double-Strand Breaks

“…There is accumulating evidence for the involvement of RNA-binding proteins in DSB repair (60). For example, Polo et al (61) reported that hnRNP U-like proteins, hnRNPUL1 and -2, positively regulate end resection at DSBs and promote repair via the HR pathway. In a genome-wide screen designed to identify the players in HR, RBMX was found to facilitate BRCA2 expression and promote HR (38).…”

Enhancement of NEIL1 Protein-initiated Oxidized DNA Base Excision Repair by Heterogeneous Nuclear Ribonucleoprotein U (hnRNP-U) via Direct Interaction

“…Because of the presence of multiple domains and motifs in this large polypeptide, hnRNP-U interacts with diverse proteins (24). A recent study described the role of hnRNP-U-like proteins hnRNP-UL1 and -2 in DNA damage signaling and end resection at double-strand breaks, which may involve a distinct motif in these large polypeptides (50). Because of its nuclear scaffold attachment, hnRNP-U (and its homologues) may target the DNA repair site to the nuclear matrix where chromatin unfolding and refolding may occur.…”