RNF168-mediated localization of BARD1 recruits the BRCA1-PALB2 complex to DNA damage.

DNA damage prompts a diverse range of alterations to the chromatin landscape. The RNF168 E3 ubiquitin ligase catalyzes the mono-ubiquitination of histone H2A at lysine (K)13/15 (mUb-H2A), forming a binding module for DNA repair proteins. BRCA1 promotes homologous recombination (HR), in part, through its interaction with PALB2, and the formation of a larger BRCA1-PALB2-BRCA2-RAD51 (BRCA1-P) complex. The mechanism by which BRCA1-P is recruited to chromatin surrounding DNA breaks is unclear. In this study, we reveal that an RNF168-governed signaling pathway is responsible for localizing the BRCA1-P complex to DNA damage. Using mice harboring a Brca1CC (coiled coil) mutation that blocks the Brca1-Palb2 interaction, we uncovered an epistatic relationship between Rnf168- and Brca1CC alleles, which disrupted development, and reduced the efficiency of Palb2-Rad51 localization. Mechanistically, we show that RNF168-generated mUb-H2A recruits BARD1 through a BRCT domain ubiquitin-dependent recruitment motif (BUDR). Subsequently, BARD1-BRCA1 accumulate PALB2-RAD51 at DNA breaks via the CC domain-mediated BRCA1-PALB2 interaction. Together, these findings establish a series of molecular interactions that connect the DNA damage signaling and HR repair machinery.

Krais JJ ，Wang Y ，Patel P ，Basu J ，Bernhardy AJ ，Johnson N ... -  《Nature Communications》

BRCA1 Haploinsufficiency Is Masked by RNF168-Mediated Chromatin Ubiquitylation.

BRCA1 functions at two distinct steps during homologous recombination (HR). Initially, it promotes DNA end resection, and subsequently it recruits the PALB2 and BRCA2 mediator complex, which stabilizes RAD51-DNA nucleoprotein filaments. Loss of 53BP1 rescues the HR defect in BRCA1-deficient cells by increasing resection, suggesting that BRCA1's downstream role in RAD51 loading is dispensable when 53BP1 is absent. Here we show that the E3 ubiquitin ligase RNF168, in addition to its canonical role in inhibiting end resection, acts in a redundant manner with BRCA1 to load PALB2 onto damaged DNA. Loss of RNF168 negates the synthetic rescue of BRCA1 deficiency by 53BP1 deletion, and it predisposes BRCA1 heterozygous mice to cancer. BRCA1+/-RNF168-/- cells lack RAD51 foci and are hypersensitive to PARP inhibitor, whereas forced targeting of PALB2 to DNA breaks in mutant cells circumvents BRCA1 haploinsufficiency. Inhibiting the chromatin ubiquitin pathway may, therefore, be a synthetic lethality strategy for BRCA1-deficient cancers.

Zong D ，Adam S ，Wang Y ，Sasanuma H ，Callén E ，Murga M ，Day A ，Kruhlak MJ ，Wong N ，Munro M ，Ray Chaudhuri A ，Karim B ，Xia B ，Takeda S ，Johnson N ，Durocher D ，Nussenzweig A ... -  《-》

BRCA1-BARD1 promotes RAD51-mediated homologous DNA pairing.

Zhao W ，Steinfeld JB ，Liang F ，Chen X ，Maranon DG ，Jian Ma C ，Kwon Y ，Rao T ，Wang W ，Sheng C ，Song X ，Deng Y ，Jimenez-Sainz J ，Lu L ，Jensen RB ，Xiong Y ，Kupfer GM ，Wiese C ，Greene EC ，Sung P ... -  《-》

A PALB2-interacting domain in RNF168 couples homologous recombination to DNA break-induced chromatin ubiquitylation.

Luijsterburg MS ，Typas D ，Caron MC ，Wiegant WW ，van den Heuvel D ，Boonen RA ，Couturier AM ，Mullenders LH ，Masson JY ，van Attikum H ... -  《-》

BARD1 reads H2A lysine 15 ubiquitination to direct homologous recombination.

Protein ubiquitination at sites of DNA double-strand breaks (DSBs) by RNF168 recruits BRCA1 and 53BP11,2, which are mediators of the homologous recombination and non-homologous end joining DSB repair pathways, respectively3. Non-homologous end joining relies on 53BP1 binding directly to ubiquitinated lysine 15 on H2A-type histones (H2AK15ub)4,5 (which is an RNF168-dependent modification6), but how RNF168 promotes BRCA1 recruitment and function remains unclear. Here we identify a tandem BRCT-domain-associated ubiquitin-dependent recruitment motif (BUDR) in BRCA1-associated RING domain protein 1 (BARD1) (the obligate partner protein of BRCA1) that, by engaging H2AK15ub, recruits BRCA1 to DSBs. Disruption of the BUDR of BARD1 compromises homologous recombination and renders cells hypersensitive to PARP inhibition and cisplatin. We further show that BARD1 binds nucleosomes through multivalent interactions: coordinated binding of H2AK15ub and unmethylated H4 lysine 20 by its adjacent BUDR and ankyrin repeat domains, respectively, provides high-affinity recognition of DNA lesions in replicated chromatin and promotes the homologous recombination activities of the BRCA1-BARD1 complex. Finally, our genetic epistasis experiments confirm that the need for BARD1 chromatin-binding activities can be entirely relieved upon deletion of RNF168 or 53BP1. Thus, our results demonstrate that by sensing DNA-damage-dependent and post-replication histone post-translation modification states, BRCA1-BARD1 complexes coordinate the antagonization of the 53BP1 pathway with promotion of homologous recombination, establishing a simple paradigm for the governance of the choice of DSB repair pathway.

Becker JR ，Clifford G ，Bonnet C ，Groth A ，Wilson MD ，Chapman JR ... -  《-》