Individuals carrying a germ line mutation of the breast cancer susceptibility gene BRCA2 are predisposed to breast, ovarian, and other types of cancer. The BRCA2 protein has been proposed to function in the repair of DNA double-strand breaks. Using an immunopurification-mass spectrometry approach to identify novel proteins that associate with the BRCA2 gene product, we found that a deubiquitinating enzyme, USP11, formed specific complexes with BRCA2. Moreover, BRCA2 was constitutively ubiquitinated in vivo in the absence of detectable proteasomal degradation. Mitomycin C (MMC) led to decreased BRCA2 protein levels associated with increased ubiquitination, consistent with proteasome-dependent degradation. While BRCA2 could be deubiquitinated by USP11 in transient overexpression assays, a catalytically inactive USP11 mutant had no effect on BRCA2 ubiquitination or protein levels. Antagonism of USP11 function either through expression of this mutant or through RNA interference increased cellular sensitivity to MMC in a BRCA2-dependent manner. All of these results imply that BRCA2 expression levels are regulated by ubiquitination in the cellular response to MMC-induced DNA damage and that USP11 participates in DNA damage repair functions within the BRCA2 pathway independently of BRCA2 deubiquitination.Individuals who carry a germ line mutation in the BRCA2 gene are predisposed to breast, ovarian, and certain other cancers (42,49). Loss of function of the wild-type BRCA2 allele is observed in breast tumors that arise in these individuals (10), defining BRCA2 as a tumor suppressor gene. Additionally, certain biallelic BRCA2 mutations have been linked to the D1 and B subtypes of the cancer susceptibility disorder Fanconi anemia (19). The BRCA2 gene encodes a 3,418-amino-acid nuclear protein (42) with an approximate molecular mass of 460 kDa (24). The BRCA2 protein has been shown to bind to the mammalian homolog of the RecA recombinase, Rad51 (9,26,37,48). Hence, a BRCA2 function in the repair of DNA double-strand breaks through homologous recombination has been proposed (37). In support of this notion, mammalian cells lacking functional BRCA2 are sensitive to DNAdamaging agents (9, 32, 37, 52), show genomic instability (32,45,52), and are deficient in homology-directed DNA repair (28,44). Furthermore, BRCA2 has been shown to possess single-stranded DNA binding ability (51) and can influence Rad51 DNA binding and recombination activities (11). However, the precise role of BRCA2 in homologous recombination and/or DNA repair has not been elucidated.The study of interacting proteins is an important approach toward understanding the biological functions of proteins. Toward this end, we immunopurified a C-terminal region of BRCA2 and subjected copurifying proteins to mass spectrometry analysis. Here we report the identification of a novel BRCA2-interacting protein, USP11, and characterize its role in BRCA2-mediated DNA damage repair.

Background Hospital capacity strain impacts quality of care and hospital throughput and may also impact the well being of clinical staff and teams as well as their ability to do their job. Institutions have implemented a wide array of tactics to help manage hospital capacity strain with variable success. Objective Through qualitative interviews, our study explored interventions used to address hospital capacity strain and the perceived impact of these interventions, as well as how hospital capacity strain impacts patients, the workforce, and other institutional priorities. Design, Setting, and Participants Qualitative study utilizing semi-structured interviews at 13 large urban academic medical centers across the USA from June 21, 2019, to August 22, 2019 (pre-COVID-19). Interviews were recorded, professionally transcribed verbatim, coded, and then analyzed using a mixed inductive and deductive method at the semantic level. Main Outcome Measures Themes and subthemes of semi-structured interviews were identified. Results Twenty-nine hospitalist leaders and hospital leaders were interviewed. Across the 13 sites, a multitude of provider, care team, and institutional tactics were implemented with perceived variable success. While there was some agreement between hospitalist leaders and hospital leaders, there was also some disagreement about the perceived successes of the various tactics deployed. We found three main themes: (1) hospital capacity strain is complex and difficult to predict, (2) the interventions that were perceived to have worked the best when facing strain were to ensure appropriate resources; however, less costly solutions were often deployed and this may lead to unanticipated negative consequences, and (3) hospital capacity strain and the tactics deployed may negatively impact the workforce and can lead to conflict. Conclusions While institutions have employed many different tactics to manage hospital capacity strain and see this as a priority, tactics seen as having the highest yield are often not the first employed. Supplementary Information The online version contains supplementary material available at 10.1007/s11606-021-07106-8.

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