RAD51 and other members of the RecA family of strand exchange proteins assemble on ssDNA to form presynaptic filaments, which carry out the central steps of homologous recombination. A microplate-based assay was developed for high-throughput measurement of hRAD51 filament formation on ssDNA. With this method, a 10,000 compound library was screened, leading to the identification of a small molecule (RS-1) that enhances hRAD51 binding in a wide range of biochemical conditions. Salt titration experiments showed that RS-1 can enhance filament stability. Ultrastructural analysis of filaments formed on ssDNA showed that RS-1 can increase both protein-DNA complex lengths and the pitch of helical filament turns. RS-1 stimulated hRAD51-mediated homologous strand assimilation (D-loop) activity by at least 5-to 11-fold, depending on the condition. This D-loop stimulation occurred even in the presence of Ca 2؉ or adenylyl-imidodiphosphate, indicating that the mechanism of stimulation was distinct from that conferred by Ca 2؉ and/or inhibition of ATPase. No D-loop activity was observed in the absence of a nucleotide triphosphate cofactor, indicating that the compound does not substitute for this requirement. These results indicate that RS-1 enhances the homologous recombination activity of hRAD51 by promoting the formation of active presynaptic filaments. Cell survival assays in normal neonatal human dermal fibroblasts demonstrated that RS-1 promotes a dose-dependent resistance to the cross-linking chemotherapeutic drug cisplatin. Given that RAD51-dependent recombination is a major determinant of cisplatin resistance, RS-1 seems to function in vivo to stimulate homologous recombination repair proficiency. RS-1 has many potential applications in both research and medical settings.cross-linking chemotherapy ͉ DNA repair ͉ high-throughput screen ͉ recombinase ͉ strand exchange H omologous recombination (HR) has multiple roles in DNA repair, including the repair of double strand breaks (DSBs) and recovery from the replication-blocking lesions formed by DNA cross-linking agents. HR repairs DSBs by locating a homologous stretch of DNA and replicating the missing genetic information from this homologous template. In contrast to DSB repair by nonhomologous end joining, HR repair generally occurs without mutations. Because of this, HR repair is critically important in the maintenance of genomic stability (reviewed in ref. 1). The proposed mechanism for this pathway begins with 5Ј to 3Ј nuclease activity at the DSB, resulting in a 3Ј singlestranded tail. The tail is coated by replication protein A, which is subsequently replaced by a helical filament of RAD51 protein. This displacement of replication protein A by RAD51 seems to be controlled by a number of mediator proteins, which include BRCA2, RAD52, and RAD51 paralogue complexes (2-5). The RAD51-coated 3Ј tail then locates and invades a homologous template of dsDNA. After invasion, templated DNA synthesis initiated at 3Ј ends leads to formation of branched DNA intermediates, which ...

Despite an increasing volume of CDs, LUT injury remained relatively uncommon (0.3 % of all CDs). Full and partial bladder injuries have unique risk profiles.

Using a large national surgical database, only 2.4% of women undergoing gynecologic cancer surgery had a concomitant POPUI procedure. Our data suggest that postoperative complications may not increase when concomitant surgery for POPUI is done at the time of gynecologic cancer surgery.

BackgroundMany senior medical students lack simple surgical and procedural skills such as knot tying.ObjectiveThe aim of this study was to determine whether viewing a Web-based expert knot-tying training video, in addition to the standard third-year medical student curriculum, will result in more proficient surgical knot tying.MethodsAt the start of their obstetrics and gynecology clerkship, 45 students were videotaped tying surgical knots for 2 minutes using a board model. Two blinded female pelvic medicine and reconstructive surgery physicians evaluated proficiency with a standard checklist (score range 0-16) and anchored scoring scale (range 0-20); higher numbers represent better skill. Students were then randomized to either (1) expert video (n=26) or (2) nonvideo (n=24) groups. The video group was provided unlimited access to an expert knot-tying instructional video. At the completion of the clerkship, students were again videotaped and evaluated.ResultsAt initial evaluation, preclerkship cumulative scores (range 0-36) on the standard checklist and anchored scale were not significantly different between the nonvideo and video groups (mean 20.3, SD 7.1 vs mean 20.2, SD 9.2, P=.90, respectively). Postclerkship scores improved in both the nonvideo and video groups (mean 28.4, SD 5.4, P<.001 and mean 28.7, SD 6.5, P=.004, respectively). Increased knot board practice was significantly correlated with higher postclerkship scores on the knot-tying task, but only in the video group (r=.47, P<.05).ConclusionsThe addition of a Web-based expert instructional video to a standard curriculum, coupled with knot board practice, appears to have a positive impact on medical student knot-tying proficiency.