Mechanism of single-stranded DNA annealing by RAD52-RPA complex.

RAD52 is important for the repair of DNA double-stranded breaks1,2, mitotic DNA synthesis3-5 and alternative telomere length maintenance6,7. Central to these functions, RAD52 promotes the annealing of complementary single-stranded DNA (ssDNA)8,9 and provides an alternative to BRCA2/RAD51-dependent homologous recombination repair10. Inactivation of RAD52 in homologous-recombination-deficient BRCA1- or BRCA2-defective cells is synthetically lethal11,12, and aberrant expression of RAD52 is associated with poor cancer prognosis13,14. As a consequence, RAD52 is an attractive therapeutic target against homologous-recombination-deficient breast, ovarian and prostate cancers15-17. Here we describe the structure of RAD52 and define the mechanism of annealing. As reported previously18-20, RAD52 forms undecameric (11-subunit) ring structures, but these rings do not represent the active form of the enzyme. Instead, cryo-electron microscopy and biochemical analyses revealed that ssDNA annealing is driven by RAD52 open rings in association with replication protein-A (RPA). Atomic models of the RAD52-ssDNA complex show that ssDNA sits in a positively charged channel around the ring. Annealing is driven by the RAD52 N-terminal domains, whereas the C-terminal regions modulate the open-ring conformation and RPA interaction. RPA associates with RAD52 at the site of ring opening with critical interactions occurring between the RPA-interacting domain of RAD52 and the winged helix domain of RPA2. Our studies provide structural snapshots throughout the annealing process and define the molecular mechanism of ssDNA annealing by the RAD52-RPA complex.

Pediatric oncology provider perspectives and patient/family perceptions of chemotherapy-induced nausea and vomiting management: Experiences at an academic medical center.

BACKGROUND: Chemotherapy-induced nausea and vomiting (CINV) is common in children undergoing cancer treatment, and significantly impacts quality of life. Clinical practice guidelines (CPGs) have been developed to guide CINV management, though many patients do not receive guideline-concordant care. Few studies have examined provider perspectives on CINV management or preferred improvement approaches, or pediatric patient perception of CINV control. METHODS: A cross-sectional study of pediatric oncology providers was conducted at a large freestanding children's hospital. Providers completed an anonymous online survey about CINV control in patients admitted for scheduled chemotherapy, and their knowledge and utilization of CINV CPGs. A survey of English and Spanish-speaking pediatric oncology patients admitted for scheduled chemotherapy was conducted to assess CINV management, with key demographics used to understand association with perceptions and adherence to antiemetic guidelines. RESULTS: For providers, 75% of respondents felt CINV management could be moderately or extremely improved, significantly more so by chemotherapy prescribers and pediatric medical residents than nurses. Over half of respondents did not have awareness of CINV CPGs, particularly pediatric medical residents. For patients, nausea was reported to be extremely well controlled in 44% of cases, and vomiting extremely well controlled in 50% of cases. There were no significant differences in patient-reported CINV across demographics, when considering emetogenicity of chemotherapy received, or concordance to guidelines. CONCLUSIONS: Implementing education in this area may help to improve provider comfort, and ultimately, the patient experience. Future studies will expand upon this novel patient perception, and develop and evaluate CINV management interventions.