Human BRCA1-BARD1 ubiquitin ligase activity counters chromatin barriers to DNA resection

The opposing activities of 53BP1 and BRCA1 influence pathway choice of DNA double-strand break repair. How BRCA1 counters the inhibitory effect of 53BP1 on DNA resection and homologous recombination is unknown. Here we identify the site of BRCA1-BARD1 required for priming ubiquitin transfer from E2~ubiquitin. We demonstrate that BRCA1-BARD1’s ubiquitin ligase activity is required for repositioning 53BP1 on damaged chromatin. We confirm H2A ubiquitylation by BRCA1-BARD1 and show that an H2A-ubiquitin fusion protein promotes DNA resection and repair in BARD1 deficient cells. We show BRCA1-BARD1 function in homologous recombination requires the chromatin remodeler SMARCAD1. SMARCAD1 binding to H2A-ubiquitin, optimal localization to sites of damage and activity in DNA repair requires its ubiquitin-binding CUE domains. SMARCAD1 is required for 53BP1 repositioning and the need for SMARCAD1 in Olaparib or camptothecin resistance is alleviated by 53BP1 loss. Thus BRCA1- BARD1 ligase activity and subsequent SMARCAD1-dependent chromatin remodeling are critical regulators of DNA repair

Photosensibilisateur spécifique pour la thérapie photodynamique ciblée des métastases péritonéales des cancers ovariens

International audienceObjectiveEpithelial ovarian cancer (EOC) management remains association of debulking surgery in combination with platinum-based chemotherapy. Sixty percent of women with EOC considered in remission will develop recurrent disease. An option to improve the completion of cytoreductive surgery may be the use of photodynamic therapy to induce necrosis of peritoneal metastases. A limit of this technique was the toxicity induced by the lack of specificity of old-generation photosensitizer (PS) for tumor tissue if the light could not be specifically applied. To solve this problem, a solution is the design of selective PS. Folate receptor is a promising target for EOC targeted therapy. We present preclinical results concerning properties of a folic-acid targeted photosensitizer.MethodPreclinical studies have been performed in vitro on murine and human cell lines of EOC and in vivo with a preclinical model of peritoneal carcinomatosis (Fisher F344 rat/NuTu-19 cell line). They aimed to precise the ability of PS to target specifically tumor tissue, to emit specific fluorescence, and to obtain cell death.ResultsTissue quantification of the PS showed specific incorporation of the folate-targeted PS within tumor tissue. Specificity for ovarian cancer metastases is better than previously reported with others photosensitizers (tumor-to-normal tissue ratio 9.6). We could detect specific fluorescence in vitro and in vivo on peritoneal metastases. Folic-acid targeted PDT allows to obtain human EOC cells death.ConclusionSpecific PS may allow the development of efficient and safe intraperitoneal PDT procedure, which could play a role in the prevention of EOC peritoneal recurrences.ObjectifLe pronostic des cancers épithéliaux de l’ovaire reste conditionné par la qualité de l’exérèse chirurgicale. Un des principaux facteurs de réduction des récidives péritonéales est l’absence de résidu macroscopique en fin d’intervention. L’association chirurgie–chimiothérapie ne prévient pas toujours la survenue de ces récidives qui concernent 60 % des femmes en rémission à l’issue de ce traitement. Parmi les hypothèses expliquant ce taux élevé de récidive, l’existence d’une maladie microscopique résiduelle en fin chirurgie est évoquée. Notre objectif est de traiter par thérapie photodynamique (PDT) les métastases péritonéales ignorées lors de la chirurgie. Le ciblage thérapeutique est indispensable. Nous présentons ici les propriétés d’un photosensibilisateur couplé à l’acide folique et ainsi dirigé vers le récepteur au folate, surexprimé par la majorité des CEO.MéthodeLe photosensibilisateur a été testé in vitro sur lignées cellulaires et in vivo sur un modèle animal de carcinose péritonéale pour l’évaluation de ses capacités à atteindre la cible tumorale, à émettre une fluorescence détectable, à induire la destruction du tissu cible.RésultatsNous avons montré la bonne spécificité de la molécule pour sa cible. Les lignées cellulaires émettent une fluorescence détectable après mise en culture dans un milieu enrichi en photosensibilisateur ce qui indique leur capacité à incorporer la molécule d’intérêt. Cette fluorescence a été détectée in vivo au niveau des métastases péritonéales. La PDT permet d’obtenir la mort cellulaire des cellules humaines in vitro avec une bonne efficacité.ConclusionUn photosensibilisateur spécifique pourrait autoriser le développement d’une technique de PDT sûre et efficace

Synthesis and Photophysical Properties of Novel Donor-Acceptor N-(Pyridin-2-yl)-Substituted Benzo(thio)amides and Their Difluoroboranyl Derivatives

quantum yield than its oxygen counterpart. The fluorescence quantum yield is much higher upon formation of theThe unprecedented N-pyridin-2-yl substituted benzo(thio)amides were prepared and subsequently converted into the cyclic difluoroboranyl (BF2) derivatives. Mass spectrometry, multinuclear NMR, IR, and elemental analysis confirmed the structure of these compounds. UV/vis and fluorescence spectroscopy as well as first-principle calculations were used to study their properties. For the first time, the influence of both the O/S replacement and presence/absence of the BF2 moiety on the photophysical properties of compounds exhibiting charge transfer properties were examined experimentally and theoretically. We show that the sulfur-containing compound has a much smaller emission difluoroboranyl complex

Synthesis and Photophysical Properties of Novel Donor–Acceptor <i>N</i>‑(Pyridin-2-yl)-Substituted Benzo(thio)amides and Their Difluoroboranyl Derivatives

The unprecedented <i>N</i>-pyridin-2-yl substituted benzo­(thio)­amides were prepared and subsequently converted into the cyclic difluoroboranyl (BF₂) derivatives. Mass spectrometry, multinuclear NMR, IR, and elemental analysis confirmed the structure of these compounds. UV/vis and fluorescence spectroscopy as well as first-principle calculations were used to study their properties. For the first time, the influence of both the O/S replacement and presence/absence of the BF₂ moiety on the photophysical properties of compounds exhibiting charge transfer properties were examined experimentally and theoretically. We show that the sulfur-containing compound has a much smaller emission quantum yield than its oxygen counterpart. The fluorescence quantum yield is much higher upon formation of the difluoroboranyl complex