Bre1/RNF20 promotes Rad51-mediated strand exchange and antagonizes the Srs2/FBH1 helicases.

Central to homologous recombination (HR) is the assembly of Rad51 recombinase on single-strand DNA (ssDNA), forming the Rad51-ssDNA filament. How the Rad51 filament is efficiently established and sustained remains partially understood. Here, we find that the yeast ubiquitin ligase Bre1 and its human homolog RNF20, a tumor suppressor, function as recombination mediators, promoting Rad51 filament formation and subsequent reactions via multiple mechanisms independent of their ligase activities. We show that Bre1/RNF20 interacts with Rad51, directs Rad51 to ssDNA, and facilitates Rad51-ssDNA filament assembly and strand exchange in vitro. In parallel, Bre1/RNF20 interacts with the Srs2 or FBH1 helicase to counteract their disrupting effect on the Rad51 filament. We demonstrate that the above functions of Bre1/RNF20 contribute to HR repair in cells in a manner additive to the mediator protein Rad52 in yeast or BRCA2 in human. Thus, Bre1/RNF20 provides an additional layer of mechanism to directly control Rad51 filament dynamics.

The RPA-RNF20-SNF2H cascade promotes proper chromosome segregation and homologous recombination repair.

The human tumor suppressor Ring finger protein 20 (RNF20)-mediated histone H2B monoubiquitination (H2Bub) is essential for proper chromosome segregation and DNA repair. However, what is the precise function and mechanism of RNF20-H2Bub in chromosome segregation and how this pathway is activated to preserve genome stability remain unknown. Here, we show that the single-strand DNA-binding factor Replication protein A (RPA) interacts with RNF20 mainly in the S and G2/M phases and recruits RNF20 to mitotic centromeres in a centromeric R-loop-dependent manner. In parallel, RPA recruits RNF20 to chromosomal breaks upon DNA damage. Disruption of the RPA-RNF20 interaction or depletion of RNF20 increases mitotic lagging chromosomes and chromosome bridges and impairs BRCA1 and RAD51 loading and homologous recombination repair, leading to elevated chromosome breaks, genome instability, and sensitivities to DNA-damaging agents. Mechanistically, the RPA-RNF20 pathway promotes local H2Bub, H3K4 dimethylation, and subsequent SNF2H recruitment, ensuring proper Aurora B kinase activation at centromeres and efficient loading of repair proteins at DNA breaks. Thus, the RPA-RNF20-SNF2H cascade plays a broad role in preserving genome stability by coupling H2Bub to chromosome segregation and DNA repair.

Value of transvaginal three-dimensional ultrasound in evaluating the curative effect of Yangmo decoction in the treatment of uterine adhesion. / ç»é˜´é“ä¸‰ç»´è¶ å£°åœ¨åˆ¤æ–­å »è†œæ–¹æ²»ç–—å®«è ”ç²˜è¿žæ•ˆæžœä¸­çš„ä»·å€¼.

OBJECTIVES: Intrauterine adhesions (IUA) is the damage of the basal layer of the endometrium caused by various reasons, resulting in adhesion of the uterine muscle walls to each other, which is manifested as clinical symptoms such as spanomenorrhea, amenorrhea, and infertility. Hysteroscopic adhesiolysis (HA) is the main treatment, for patients with moderate or severe adhesion or angular adhesion, the incidence of postoperative adhesion is high. Traditional Chinese medicine "Yangmo decoction" can promote endometrial growth. Three-dimensional transvaginal ultrasonography (3D-TVUS) can judge IUA and evaluate uterine receptivity through three-dimensional imaging. This study aims to investigate the value of 3D-TVUS in judging the efficacy of Yangmo decoction in the treatment of intrauterine adhesions. METHODS: The clinical data of patients who underwent HA at two different centers in department of Gynecology of Third Xiangya Hospital of Central South University and Changsha Jiangwan Hospital from January 2021 to August 2021 were retrospectively collected. A total of 275 eligible patients were included. According to the postoperative management measures, the selected patients were divided into two groups. Yangmo decoction group (n=138): the use of Yangmo decoction and uterine-shaped silicon stent post HA; Hormone group (n=137): the use of estrogen, progesterone and uterine-shaped silicon stent post HA. The preoperative general data, preoperative and postoperative 3D-TVUS parameters of the two groups were analyzed. RESULTS: The endometrial thickness of Yangmo decoction group was thicker than that of hormone group (P<0.001), the intercornual distance was wider (P=0.016), the endometrial echo was more homogeneous (P=0.018), the percentage of bilaterally visible tubal opening was higher (P<0.001), the endometrial morphology was better (P=0.012), and endometrial blood flow, endometrial motility and uterine motion were better in Yangmo decoction group than that in the hormone group (all P<0.001). CONCLUSIONS: The endometrial thickness, echo, blood flow, and peristalsis, the number of visible tubal opening, uterine motion, and the intercornual distance obtained by 3D-TVUS examination are important factors to evaluate the prognosis of postoperative drug treatment for IUA. 3D-TVUS is of great significance in evaluating the efficacy of Yangmo decoction in the treatment of IUA.

Comparison of high-intensity focused ultrasound ablation and uterine artery embolization in the management of cervical pregnancy.

Background: Cervical pregnancy (CP) is an uncommon type of ectopic pregnancy with a rising risk to life. Currently, there is no universal protocol for the safe and effective management of CP. This study aimed to investigate the clinical efficacy of high-intensity focused ultrasound ablation (HIFU) vs. uterine artery embolization (UAE) in the management of CP to develop a standard for the treatment of CP. Methods: From January 2015 to October 2021, 36 patients with CP were diagnosed, treated, and followed up at the Department of Gynecology of Third Xiangya Hospital of Central South University. A total of 11 patients were treated with HIFU followed by suction curettage under hysteroscopic guidance, and 25 patients were treated with UAE followed by suction curettage under hysteroscopic guidance. Medical records and pregnancy outcomes were retrospectively analyzed. Results: Compared to the UAE group, the HIFU group had a shorter interval time (1.5 ± 0.21 days vs. 2.6 ± 0.26 days), shorter duration of hospitalization (5.5 ± 0.31 days vs. 6.6 ± 0.21 days), shorter recovery time of menstruation (30.6 ± 7.09 days vs. 36.9 ± 5.54 days), fewer adverse reactions (0/11 vs. 9/25), and fewer postoperative complications (1/11 vs. 8/25). There were no significant differences in age, gravidity, parity, abortion, gestational age, cardiac pulsation, admission symptoms, hemoglobin level, largest diameter of the sac/mass, serum human chorionic gonadotropin (hCG) level at admission, hospitalization expenses, hospitalization days, blood loss during curettage, degree of hCG decline, residue after curettage, fertility requirement, and pregnancy outcomes. Conclusion: Both HIFU and UAE are safe and effective in the treatment of patients with CP. Compared to UAE, HIFU treatment for CP is a safer and more effective therapeutic schedule owing to the advantages of being more minimally invasive, shorter interval time, shorter hospitalization days and recovery time of menstruation, fewer adverse reactions, and fewer postoperative complications.

RPA-mediated recruitment of Bre1 couples histone H2B ubiquitination to DNA replication and repair.

The ubiquitin E3 ligase Bre1-mediated H2B monoubiquitination (H2Bub) is essential for proper DNA replication and repair in eukaryotes. Deficiency in H2Bub causes genome instability and cancer. How the Bre1-H2Bub pathway is evoked in response to DNA replication or repair remains unknown. Here, we identify that the single-stranded DNA (ssDNA) binding factor RPA acts as a key mediator that couples Bre1-mediated H2Bub to DNA replication and repair in yeast. We found that RPA interacts with Bre1 in vitro and in vivo, and this interaction is stimulated by ssDNA. This association ensures the recruitment of Bre1 to replication forks or DNA breaks but does not affect its E3 ligase activity. Disruption of the interaction abolishes the local enrichment of H2Bub, resulting in impaired DNA replication, response to replication stress, and repair by homologous recombination, accompanied by increased genome instability and DNA damage sensitivity. Notably, we found that RNF20, the human homolog of Bre1, interacts with RPA70 in a conserved mode. Thus, RPA functions as a master regulator for the spatial-temporal control of H2Bub chromatin landscape during DNA replication and recombination, extending the versatile roles of RPA in guarding genome stability.