MERIT40 controls BRCA1–Rap80 complex integrity and recruitment to DNA double-strand breaks

Abstract

Rap80 targets the breast cancer suppressor protein BRCA1 along with Abraxas and the BRCC36 deubiquitinating enzyme (DUB) to polyubiquitin structures at DNA double-strand breaks (DSBs). These DSB targeting events are essential for BRCA1-dependent DNA damage response-induced checkpoint and repair functions. Here, we identify MERIT40 (Mediator of Rap80 Interactions and Targeting 40 kD)/(C19orf62) as a Rap80-associated protein that is essential for BRCA1-Rap80 complex protein interactions, stability, and DSB targeting. Moreover, MERIT40 is required for Rap80-associated lysine 63 -ubiquitin DUB activity, a critical component of BRCA1-Rap80 G2 checkpoint and viability responses to ionizing radiation. Thus, MERIT40 represents a novel factor that links BRCA1-Rap80 complex integrity, DSB recognition, and ubiquitin chain hydrolytic activities to the DNA damage response. These findings provide new molecular insights into how BRCA1 associates with independently assembled core protein complexes to maintain genome integrity.[Keywords: C19orf62; HSPC142; MERIT40; BRCA1; Rap80; Abraxas; BRCC36] Supplemental material is available at http://www.genesdev.org.

NBA1/MERIT40 and BRE Interaction Is Required for the Integrity of Two Distinct Deubiquitinating Enzyme BRCC36-containing Complexes

“…Complex-Previously, we and others have found that NBA1 is required for cells to maintain proper levels of Abraxas, BRE, and BRCC36 (16,17,23). We found that NBA1 is also required for maintaining the levels of ABRO1 protein (Fig.…”

“…In addition, its N terminus contains multiple serine residues that were reported phosphorylated in largescale proteomic analysis for phosphorylation sites on the proteins (24 -28). Its C-terminal 310 -314 amino acids have been suggested to be important for its localization to DNA damage sites (23). Thus, we generated deletion mutants for the N ter-minus and C terminus of the NBA1 protein, as well as point mutants in the VWA-domain for amino acids that are conserved either among various VWA domains or among NBA1 proteins from different species (16).…”

Degradation of Human RAP80 is Cell Cycle Regulated by Cdc20 and Cdh1 Ubiquitin Ligases

“…The BRCA1-A complex contains many subunits, including a coiled coil domain-containing protein (CCDC98/ABRAXAS), the BRCA1/BRCA2-containing complex subunit 45/brain and reproductive organ-expressed protein (BRCC45/BRE), the BRCA1/BRCA2-containing complex subunit 36 (BRCC36), mediator of RAP80 interactions and targeting subunit of 40/new component of the BRCA1-A complex (MERIT40/NBA1), and breast cancer 1 (BRCA1; refs. [6][7][8][9][10][11][12][13][14]. This recruitment is required for the activity of BRCA1 at the DNA damage checkpoint and for DNA repair.…”

“…Receptor-associated protein 80 (RAP80) plays an important role in signal transduction in the DNA damage response by recruiting the BRCA1-A complex to DNA damage sites in a lysine 63-mediated polyubiquitin-binding dependent manner (6)(7)(8)(9)(10)(11)(12)(13)(14). The BRCA1-A complex contains many subunits, including a coiled coil domain-containing protein (CCDC98/ABRAXAS), the BRCA1/BRCA2-containing complex subunit 45/brain and reproductive organ-expressed protein (BRCC45/BRE), the BRCA1/BRCA2-containing complex subunit 36 (BRCC36), mediator of RAP80 interactions and targeting subunit of 40/new component of the BRCA1-A complex (MERIT40/NBA1), and breast cancer 1 (BRCA1; refs.…”

The role of K63‐linked polyubiquitination in cardiac hypertrophy

“…Apart from this, lysine 6‐, 11‐, 27‐ and 29‐linked polyubiquitination promotes the degradation of proteins in a 26S proteasome apparatus‐dependent manner. While K63‐linked ubiquitination of proteins contributes to various essential cellular activities including signal transduction, protein trafficking, protein‐protein interaction and DNA damage response 6, 7. Recent evidence suggests that K63‐linked ubiquitination is functionally important for various biological functions including cell cycle progression, immune response, autophagy and neural cell functions 8, 9, 10.…”