Valosin-containing Protein (VCP)/p97 Segregase Mediates Proteolytic Processing of Cockayne Syndrome Group B (CSB) in Damaged Chromatin.

Cockayne syndrome group A and B (CSB) proteins act in transcription-coupled repair, a subpathway of nucleotide excision repair. Here we demonstrate that valosin-containing protein (VCP)/p97 segregase functions in ultraviolet radiation (UVR)-induced ubiquitin-mediated CSB degradation. We show that VCP/p97 inhibition and siRNA-mediated ablation of VCP/p97 and its cofactors UFD1 and UBXD7 impair CSB degradation. VCP/p97 inhibition also results in the accumulation of CSB in chromatin. Moreover, VCP/p97 interacts with both native and ubiquitin-conjugated forms of CSB. The localized cellular UVR exposures lead to VCP/p97 accumulation at DNA damage spots, forming distinct UVR-induced foci. However, manifestation of VCP/p97 foci is independent of CSB and UBXD7. Furthermore, VCP/p97 and UBXD7 associate with the Cockayne syndrome group A-DDB1-Cul4A complex, an E3 ligase responsible for CSB ubiquitination. Compromising proteasome and VCP/p97 function allows accumulation of both native and ubiquitinated CSB and results in an increase of UBXD7, proteasomal RPN2, and Sug1 in the chromatin compartment. Surprisingly, both biochemical inhibition and genetic defect of VCP/p97 enhance the recovery of RNA synthesis following UVR, whereas both VCP/p97 and proteasome inhibitions decrease cell viability. Our findings reveal a new role of VCP/p97 segregase in the timely processing of ubiquitinated CSB from damaged chromatin.

Ubiquitin-specific protease 7 regulates nucleotide excision repair through deubiquitinating XPC protein and preventing XPC protein from undergoing ultraviolet light-induced and VCP/p97 protein-regulated proteolysis.

Ubiquitin specific protease 7 (USP7) is a known deubiquitinating enzyme for tumor suppressor p53 and its downstream regulator, E3 ubiquitin ligase Mdm2. Here we report that USP7 regulates nucleotide excision repair (NER) via deubiquitinating xeroderma pigmentosum complementation group C (XPC) protein, a critical damage recognition factor that binds to helix-distorting DNA lesions and initiates NER. XPC is ubiquitinated during the early stage of NER of UV light-induced DNA lesions. We demonstrate that transiently compromising cellular USP7 by siRNA and chemical inhibition leads to accumulation of ubiquitinated forms of XPC, whereas complete USP7 deficiency leads to rapid ubiquitin-mediated XPC degradation upon UV irradiation. We show that USP7 physically interacts with XPC in vitro and in vivo. Overexpression of wild-type USP7, but not its catalytically inactive or interaction-defective mutants, reduces the ubiquitinated forms of XPC. Importantly, USP7 efficiently deubiquitinates XPC-ubiquitin conjugates in deubiquitination assays in vitro. We further show that valosin-containing protein (VCP)/p97 is involved in UV light-induced XPC degradation in USP7-deficient cells. VCP/p97 is readily recruited to DNA damage sites and colocalizes with XPC. Chemical inhibition of the activity of VCP/p97 ATPase causes an increase in ubiquitinated XPC on DNA-damaged chromatin. Moreover, USP7 deficiency severely impairs the repair of cyclobutane pyrimidine dimers and, to a lesser extent, affects the repair of 6-4 photoproducts. Taken together, our findings uncovered an important role of USP7 in regulating NER via deubiquitinating XPC and by preventing its VCP/p97-regulated proteolysis.

p38 MAPK- and Akt-mediated p300 phosphorylation regulates its degradation to facilitate nucleotide excision repair.

Besides the primary histone acetyltransferase (HAT)-mediated chromatin remodeling function, co-transcriptional factor, p300, is also known to play a distinct role in DNA repair. However, the exact mechanism of p300 function in DNA repair has remained unclear and difficult to discern due to the phosphorylation and degradation of p300 in response to DNA damage. Here, we have demonstrated that p300 is only degraded in the presence of specific DNA lesions, which are the substrates of nucleotide excision repair (NER) pathway. In contrast, DNA double-strand breaks fail to degrade p300. Degradation is initiated by phosphorylation of p300 at serine 1834, which is catalyzed by the cooperative action of p38 mitogen-activated protein kinases and Akt kinases. In depth, functional analysis revealed that (i) p300 and CBP act redundantly in repairing ultraviolet (UV) lesions, (ii) the phosphorylation of p300 at S1834 is critical for efficient removal of UV-induced cyclobutane pyrimidine dimers and (iii) p300 is recruited to DNA damage sites located within heterochromatin. Taken together, we conclude that phosphorylated p300 initially acetylates histones to relax heterochromatin to allow damage recognition factors access to damage DNA. Thereupon, p300 is promptly degraded to allow the sequential recruitment of downstream repair proteins for successful execution of NER.

Arthroscopy-assisted surgery for tibial plateau fractures.

PURPOSE: This study aimed to summarize the recent clinical outcomes of patients undergoing arthroscopy-assisted reduction and internal fixation (ARIF) for tibial plateau fractures. METHODS: A systematic electronic search of the PubMed and Cochrane databases was performed in January 2014. All English-language clinical studies on tibial plateau fractures treated with ARIF that were published after January 1, 2000 were eligible for inclusion. Basic information related to the surgery was collected. RESULTS: The search criteria initially identified 141 articles, and 19 studies were included in this systematic review. There were 2 retrospective comparative studies, 16 case series studies, and one clinical series based on a technique note. There were a total of 609 patients in this systematic review, with a mean follow-up time of 52.5 months. The most common fracture types were Schatzker types II and III. Concomitant injuries were common: 42.2% of the patients had meniscal injuries, and 21.3% had anterior cruciate ligament (ACL) injuries. In addition, the status of 90.5% of the patients was classified as good or excellent according to the clinical Rasmussen scoring system, and 90.9% of the patients were satisfied with the treatment. Only 6 severe complications were reported, including one case of compartment syndrome. CONCLUSIONS: ARIF is a reliable, effective, and safe method for the treatment of tibial plateau fractures, especially when they present with concomitant injuries. LEVEL OF EVIDENCE: Level IV, systematic review of Level III and Level IV studies.

[Observation of curative effect in treatment of distal tibial fractures with minimall invasive percutaneous technique].

OBJECTIVE: To explore the application of minimally invasive percutaneous plate osteosynthesis (MIPPO) the clinical curative effect of treatment of fractures of the distal tibia. METHODS: From 2010 June to 2014 June, the application of MIPPO technology combined with LCP (low bend medial distal tibial plates) for treatment of 67 cases of distal tibial fracture patients, to evaluate the healing of fracture, function etc. RESULTS: 67 patients with effective follow-up, time was 6-20 months, mean 15 months. The incision healed in one stage, 3 weeks. The effect of 12-16 weeks to fracture healing standard weight, nomalunion and nonunion cases, no fracture, bone plate and screw loosening, exit and other phenomena. The postoperative function was evaluated according to Johner-Wruch criteria, excellent in 45 cases, good in 16 cases, 6 cases, poor in 0 cases. CONCLUSION: MIPPO technique combined with LCP (low bend medial distal tibial plates) in treatment of distal tibial fractures in accord with biological osteosynthesis requirements, is a recommendable method to treat fracture extension.

Frequency and Risk Factors of Deep Venous Thrombosis in Aged Patients with Intertrochanteric Fracture on Admission.

OBJECTIVE: To investigate the frequency of deep vein thrombosis (DVT) in patients aged over 80 years on admission after intertrochanteric femur fracture and to explore the risk factors of DVT. STUDY DESIGN: Descriptive study. Place and Duration of the Study: Department of Orthopaedics, China-Japan Friendship Hospital, Beijing, China, from 1st January 2019 to 31st December 2022. METHODOLOGY: A group of patients aged over 80 years with intertrochanteric fracture were included according to the presence or absence of DVT confirmed by ultrasonography on admission. The patients were divided into the non-DVT and DVT groups. Clinical data were retrospectively compared between the two groups and analysed by multivariate logistic regression to screen risk factors of DVT. RESULTS: A total of 130 patients meeting the inclusion criteria were enrolled, and 37 of them had DVT on admission, with a prevalence of 28.5%, including 25 (67.6%) distal peripheral DVT, 11 (29.7%) proximal central DVT, and 1 (2.7%) mixed DVT. The American Society of Anaesthesiologists (ASA) classification, Charlson comorbidity index, the serum levels of D-dimer, fibrinogen degradation products, albumin, potassium, inorganic phosphorus, and calcium showed significant differences between the two groups (p <0.1). Multivariate analysis identified increased D-dimer (>6.005 mg/L), decreased albumin (<36.45 g/L), and reduced potassium (<3.650 mmol/L) as independent factors for DVT in aged intertrochanteric fracture patients (AIFPs). CONCLUSION: A high incidence of DVT was revealed in AIFPs, and elevated D-dimer levels, reduced albumin levels, and reduced potassium concentrations were shown to be correlated to DVT. KEY WORDS: Intertrochanteric fracture, Deep vein thrombosis, Aged patients, Risk factor, Multivariate logistic regression.

Chk1 Inhibition Hinders the Restoration of H3.1K56 and H3.3K56 Acetylation and Reprograms Gene Transcription After DNA Damage Repair.

H3K56 acetylation (H3K56Ac) was reported to play a critical role in chromatin assembly; thus, H3K56ac participates in the regulation of DNA replication, cell cycle progression, DNA repair, and transcriptional activation. To investigate the influence of DNA damage regulators on the acetylation of histone H3 and gene transcription, U2OS cells expressing SNAP-labeled H3.1 or SNAP-labeled H3.3 were treated with ATM, ATR, or a Chk1 inhibitor after ultraviolet (UV) radiation. The levels of H3.1K56ac, H3.3K56ac, and other H3 site-specific acetylation were checked at different time points until 24 h after UV radiation. The difference in gene transcription levels was also examined by mRNA sequencing. The results identified Chk1 as an important regulator of histone H3K56 acetylation in the restoration of both H3.1K56ac and H3.3K56ac. Moreover, compromising Chk1 activity via chemical inhibitors suppresses gene transcription after UV radiation. The study suggests a previously unknown role of Chk1 in regulating H3K56 and some other site-specific H3 acetylation and in reprograming gene transcription during DNA damage repair.

Quantitative proteomics reveals potential anti-inflammatory protein targets of radial extracorporeal shock wave therapy in TNF-α-induced model of acute inflammation in primary human tenocytes.

Tendinopathy refers to a type of tendon disease with a multifactorial spectrum. Recent research has begun to reveal the effects of inflammation on the tendinopathic process, especially in the first stage of tendinopathy. Radial extracorporeal shock wave therapy (rESWT) has been successfully used to treat orthopedic diseases. However, the molecular mechanisms underlying the anti-inflammatory effects of rESWT on tumor necrosis factor-α treated tenocytes have not been fully elucidated. In this study, we applied total protein tandem mass tag-labeled quantitative proteomics with liquid chromatography-mass spectrometer/mass spectrometer technology to identify differentially expressed proteins (DEPs) among inflammatory tenocytes, rESWT inflammatory tenocytes, and controls using three biological replicates. Human tenocytes were used and they were cultured in vitro. In total, 1028 and 40 DEPs were detected for control versus inflammatory tenocytes and for inflammatory tenocytes versus rESWT inflammatory tenocytes, respectively. Further, we identified integrin α2, selenoprotein S, and NLR family CARD domain-containing protein 4 as pivotal molecular targets of the anti-inflammatory effects of rESWT. This is the first study to provide a reference proteomic map for inflammatory tenocytes and rESWT inflammatory tenocytes. Our findings provide crucial insight into the molecular mechanisms underscoring the anti-inflammatory effects of rESWT in tendinopathy.

Thymoquinone up-regulates PTEN expression and induces apoptosis in doxorubicin-resistant human breast cancer cells.

The use of innocuous naturally occurring compounds to overcome drug resistance and cancer recalcitrance is now in the forefront of cancer research. Thymoquinone (TQ) is a bioactive constituent of the volatile oil derived from seeds of Nigella sativa Linn. TQ has shown promising anti-carcinogenic and anti-tumor activities through different mechanisms. However, the effect of TQ on cell signaling and survival pathways in resistant cancer cells has not been fully delineated. Here, we report that TQ greatly inhibits doxorubicin-resistant human breast cancer MCF-7/DOX cell proliferation. TQ treatment increased cellular levels of PTEN proteins, resulting in a substantial decrease of phosphorylated Akt, a known regulator of cell survival. The PTEN expression was accompanied with elevation of PTEN mRNA. TQ arrested MCF-7/DOX cells at G2/M phase and increased cellular levels of p53 and p21 proteins. Flow cytometric analysis and agarose gel electrophoresis revealed a significant increase in Sub-G1 cell population and appearance of DNA ladders following TQ treatment, indicating cellular apoptosis. TQ-induced apoptosis was associated with disrupted mitochondrial membrane potential and activation of caspases and PARP cleavage in MCF-7/DOX cells. Moreover, TQ treatment increased Bax/Bcl2 ratio via up-regulating Bax and down-regulating Bcl2 proteins. More importantly, PTEN silencing by target specific siRNA enabled the suppression of TQ-induced apoptosis resulting in increased cell survival. Our results reveal that up-regulation of the key upstream signaling factor, PTEN, in MCF-7/DOX cells inhibited Akt phosphorylation, which ultimately causes increase in their regulatory p53 levels affecting the induction of G2/M cell cycle arrest and apoptosis. Overall results provide mechanistic insights for understanding the molecular basis and utility of the anti-tumor activity of TQ.

Timely upstream events regulating nucleotide excision repair by ubiquitin-proteasome system: ubiquitin guides the way.

The ubiquitin-proteasome system (UPS) plays crucial roles in regulation of multiple DNA repair pathways, including nucleotide excision repair (NER), which eliminates a broad variety of helix-distorting DNA lesions that can otherwise cause deleterious mutations and genomic instability. In mammalian NER, DNA damage sensors, DDB and XPC acting in global genomic NER (GG-NER), and, CSB and RNAPII acting in transcription-coupled NER (TC-NER) sub-pathways, undergo an array of post-translational ubiquitination at the DNA lesion sites. Accumulating evidence indicates that ubiquitination orchestrates the productive assembly of NER preincision complex by driving well-timed compositional changes in DNA damage-assembled sensor complexes. Conversely, the deubiquitination is also intimately involved in regulating the damage sensing aftermath, via removal of degradative ubiquitin modification on XPC and CSB to prevent their proteolysis for the factor recycling. This review summaries the relevant research efforts and latest findings in our understanding of ubiquitin-mediated regulation of NER and active participation by new regulators of NER, e.g., Cullin-Ring ubiquitin ligases (CRLs), ubiquitin-specific proteases (USPs) and ubiquitin-dependent segregase, valosin-containing protein (VCP)/p97. We project hypothetical step-by-step models in which VCP/p97-mediated timely extraction of damage sensors is integral to overall productive NER. The USPs and proteasome subtly counteract in fine-tuning the vital stability and function of NER damage sensors.

Spironolactone-induced XPB degradation requires TFIIH integrity and ubiquitin-selective segregase VCP/p97.

Mineralocorticoid and androgen receptor antagonist, spironolactone, was recently identified as an inhibitor of nucleotide excision repair (NER), acting via induction of proteolysis of TFIIH component Xeroderma Pigmentosum B protein (XPB). This activity provides a strong rationale for repurposing spironolactone for cancer therapy. Here, we report that the spironolactone-induced XPB proteolysis is mediated through ubiquitin-selective segregase, valosin-containing protein (VCP)/p97. We show that spironolactone induces a dose- and time-dependent degradation of XPB but not XPD, and that the XPB degradation is blocked by VCP/p97 inhibitors DBeQ, NMS-873, and neddylation inhibitor MLN4924. Moreover, the cellular treatment by VCP/p97 inhibitors leads to the accumulation of ubiquitin conjugates of XPB but not XPD. VCP/p97 knockdown by inducible shRNA does not affect XPB level but compromises the spironolactone-induced XPB degradation. Also, VCP/p97 interacts with XPB upon treatment of spironolactone and proteasome inhibitor MG132, while the VCP/p97 adaptor UBXD7 binds XPB and its ubiquitin conjugates. Additionally, ATP analog-mediated inhibition of Cdk7 significantly decelerates spironolactone-induced XPB degradation. Likewise, engaging TFIIH to NER by UV irradiation slows down spironolactone-induced XPB degradation. These results indicate that the spironolactone-induced XPB proteolysis requires VCP/p97 function and that XPB within holo-TFIIH rather than core-TFIIH is more vulnerable to spironolactone-induced proteolysis. Abbreviations NER: nucleotide excision repair; TFIIH: transcription factor II H; CAK: Cdk-activating kinase (CAK) complex; XPB: Xeroderma Pigmentosum type B; VCP/p97: valosin-containing protein/p97; Cdk7: cyclin-dependent kinase 7; NAE: NEDD8-activating enzyme; IP: immunoprecipitation.

Investigation of perioperative blood loss of femoral shaft fractures treated with intramedullary nail or locking compression plate.

INTRODUCTION: Femoral shaft fractures (FSFs) are associated with significant blood loss, resulting in anemia and hemorrhagic shock. However, there has been limited data for the blood loss of FSFs during the whole perioperative period. Our primary aim is to quantify the blood loss associated with FSFs treated with intramedullary nail or locking compression plate fixation, as well as to identify the relative affecting factors for perioperative hidden blood loss (HBL). PATIENTS AND METHODS: 131 consecutive patients with FSFs were enrolled in the retrospective study between January 2009 and January 2020, including 90 cases for intramedullary nail (Nail group) and 41 cases for locking compression plate fixation (Plate group). Demographics and perioperative data were collected and analyzed. Total blood loss (TBL), visible blood loss (VBL), HBL, and percentage of HBL (PHBL) were calculated based on hematocrit (Hct) changes. RESULTS: There was a large drop of hemoglobin (Hb) during the perioperative time. Of all 131 patients, the average HBL was 1445.5 ± 443.2 mL, accounting for 78.7% of TBL (1815.1 ± 446.3 mL). TBL and HBL in Nail group were 1886.1 ± 438.6 mL and 1546.0 ± 424.7 mL; while TBL and HBL in Plate group were 1659.5 ± 427.9 mL and 1225.1 ± 405.7 mL. The differences between the two groups were statistically significant (p = 0.007, p < 0.001, respectively). Besides, statistical significance (p< 0.05, p< 0.05, respectively) was also reported in HBL between Type-A and Type-C, and between Type-B and Type-C (1395.8 ± 444.8 mL vs. 1651.6 ± 495.7 mL; and 1411.2 ± 383.4 mL vs. 1651.6 ± 495.7 mL, respectively). CONCLUSIONS: Patients of FSFs had significant TBL and HBL, the amount of which was much larger than that observed intra-operatively. Moreover, two readily available preoperative factors for nail fixation and Type-C were associated with a higher likelihood of more HBL. Therefore, it was argued that regular perioperative monitoring and timely blood transfusion were crucially important for patients to avoid possible risks of anemia and facilitate recovery.

Histone modifications: crucial elements for damage response and chromatin restoration.

Eukaryotic genomes are packaged into chromatin from repeated nucleosome arrays in which DNA sequences wrap around histones. Chromatin organization has profound influence on DNA-templated processes such as transcription, DNA replication, and repair. Recent studies have also revealed chromatin dynamics as an active contributor to diverse DNA damage responses (DDR). Here, we review recent progress in histone modification related to DDR and post-repair chromatin restoration at the sites of DNA damage. We discuss how the timing and features of histone modifications would provide the initial as well as the final guidance for DDR, and the prospect that modifications may challenge the epigenetic stability of repaired cells and serve as damage memory in chromatin.

Chromatin restoration following nucleotide excision repair involves the incorporation of ubiquitinated H2A at damaged genomic sites.

Restoration of functionally intact chromatin structure following DNA damage processing is crucial for maintaining genetic and epigenetic information in human cells. Here, we show the UV-induced uH2A foci formation in cells lacking XPC, DDB2, CSA or CSB, but not in cells lacking XPA, XPG or XPF indicating that uH2A incorporation relied on successful damage repair occurring through either GGR or TCR sub-pathway. In contrast, XPA, XPG or XPF were not required for formation of gammaH2AX foci in asynchronous cells. Notably, the H2A ubiquitin ligase Ring1B, a component of Polycomb repressor complex 1, did not localize at DNA damage sites. However, histone chaperone CAF-1 showed distinct localization to the damage sites. Knockdown of CAF-1 p60 abolished CAF-1 as well as uH2A foci formation. CAF-1 p150 was found to associate with NER factors TFIIH, RPA p70 and PCNA in chromatin. These data demonstrate that successful NER of genomic lesions and prompt CAF-1-mediated chromatin restoration link uH2A incorporation at the sites of damage repair within chromatin.

USP7-mediated deubiquitination differentially regulates CSB but not UVSSA upon UV radiation-induced DNA damage.

Cockayne syndrome group B (CSB) protein participates in transcription-coupled nucleotide excision repair. The stability of CSB is known to be regulated by ubiquitin-specific protease 7 (USP7). Yet, whether USP7 acts as a deubiquitinating enzyme for CSB is not clear. Here, we demonstrate that USP7 deubiquitinates CSB to maintain its levels after ultraviolet (UV)-induced DNA damage. While both CSB and UV-stimulated scaffold protein A (UVSSA) exhibit a biphasic decrease and recovery upon UV irradiation, only CSB recovery depends on USP7, which physically interacts with and deubiquitinates CSB. Meanwhile, CSB overexpression stabilizes UVSSA, but decrease UVSSA's presence in nuclease-releasable/soluble chromatin, and increase the presence of ubiquitinated UVSSA in insoluble chromatin alongside CSB-ubiquitin conjugates. Remarkably, CSB overexpression also decreases CSB association with USP7 and UVSSA in soluble chromatin. UVSSA exists in several ubiquitinated forms, of which mono-ubiquitinated form and other ubiquitinated UVSSA forms are detectable upon 6xHistidine tag-based purification. The ubiquitinated UVSSA forms, however, are not cleavable by USP7 in vitro. Furthermore, USP7 disruption does not affect RNA synthesis but decreases the recovery of RNA synthesis following UV exposure. These results reveal a role of USP7 as a CSB deubiquitinating enzyme for fine-tuning the process of TC-NER in human cells.

Ubiquitylation-independent degradation of Xeroderma pigmentosum group C protein is required for efficient nucleotide excision repair.

The Xeroderma Pigmentosum group C (XPC) protein is indispensable to global genomic repair (GGR), a subpathway of nucleotide excision repair (NER), and plays an important role in the initial damage recognition. XPC can be modified by both ubiquitin and SUMO in response to UV irradiation of cells. Here, we show that XPC undergoes degradation upon UV irradiation, and this is independent of protein ubiquitylation. The subunits of DDB-Cul4A E3 ligase differentially regulate UV-induced XPC degradation, e.g DDB2 is required and promotes, whereas DDB1 and Cul4A protect the protein degradation. Mutation of XPC K655 to alanine abolishes both UV-induced XPC modification and degradation. XPC degradation is necessary for recruiting XPG and efficient NER. The overall results provide crucial insights regarding the fate and role of XPC protein in the initiation of excision repair.

Prevalence and associated factors of intra-articular lesions in acute ankle fractures evaluated by arthroscopy and clinical outcomes with minimum 24-month follow-up.

BACKGROUND: Acute ankle fractures can lead to high rate of concomitant intra-articular lesions which may compromise clinical results. The purpose of this study was to evaluate the incidence of concomitant intra-articular lesions in acute ankle fractures with arthroscopy. We also sought to analyze the relationship between intra-articular lesions and the fracture type, as well as the severity of the fracture. METHODS: It was a retrospective cohort study. From April 2014 to December 2015, we have chosen arthroscopy-assisted open reduction and internal fixation (AORIF) for the treatment of unstable acute ankle fractures. All concomitant intra-articular lesions were assessed and documented carefully and prospectively, such as ligament injuries, osteochondral lesions, and tibiofibular syndesmosis injuries. All fractures were classified according to the Lauge-Hansen classification system. The American Orthopedic Foot and Ankle Society's (AOFAS) ankle-hindfoot scale was used to assess post-operative function. Statistical comparisons between the intra-articular lesions, the fracture type, and the severity of the presenting fracture were performed using a Chi-squared analysis. RESULTS: Data of 36 patients were analyzed in the study, including 23 supination-type fractures and 13 pronation-type fractures. The incidence of tibiofibular syndesmosis injuries, chondral lesions, and loose bodies were 92%, 72%, and 39%, respectively. Avulsion fractures of the anterior tibiofibular syndesmosis were more commonly found in supination-type fractures than pronation-type fracture (45% vs. 15%, χ = 5.78, P = 0.02), which would cause mechanical blocking in the anterior portion of the ankle. On the contrary, chondral lesions were more commonly found in the more severe fractures than mild fractures (86% vs. 53%, χ = 4.57, P = 0.03). A mean 41.7 months (range, 33.0-51.0 months) of follow-up was achieved. A mean AOFAS's ankle-hindfoot scale was 96.9, and 97.2% of the patients were satisfied with the procedure. CONCLUSIONS: Acute ankle fractures have a high incidence of concomitant intra-articular lesions. Avulsion fractures of the anterior tibiofibular syndesmosis are more commonly found in supination-type fractures. Chondral lesions are related to the severity of the fractures, but not with the classification of the fractures. AORIF can be one reliable solution in dealing with the associated injuries seen with acute ankle fractures.

Role of Claspin in regulation of nucleotide excision repair factor DDB2.

The replication checkpoint protein Claspin is important for maintenance of genomic stability and is required for cells to overcome genotoxic stress. Upon UV-induced DNA damage, Claspin is required for activation of the ATR-mediated DNA damage checkpoint response, leading to arrest of DNA replication and inhibition of cell cycle progression. Located at the DNA replication fork, Claspin is also suggested to monitor replication and sense damage. Our present studies in HeLa cells demonstrate associations between the Claspin/ATR-related DNA damage checkpoint response and the global genomic nucleotide excision repair pathway. siRNA-mediated knockdown of Claspin abolishes the UV-induced degradation of DDB2 and impairs the co-localization of DDB2 to DNA damage sites. Thus, the presence of Claspin is required for the total turnover of DNA damage binding protein DDB2, as well as for its functionality in DNA damage recognition. Claspin, however, seems not to be required for maintaining the cellular level of the NER factor XPC and its UV-induced post-translational modifications. Co-localization of XPC with DNA lesions is also intact in the absence of Claspin as is the repair of the UV-induced lesions CPD and 6-4PP. Claspin itself may be directly responsible for physical interaction between the two pathways since Claspin is able to associate with DDB1, DDB2 and XPC. Taken together, these findings reveal physical and functional interplay between Claspin and NER-related proteins and demonstrate crosstalk between the DNA damage checkpoint control and DNA damage repair pathways.

Naringenin protects HaCaT human keratinocytes against UVB-induced apoptosis and enhances the removal of cyclobutane pyrimidine dimers from the genome.

Many naturally occurring agents are believed to protect against UV-induced skin damage. In this study, we have investigated the effects of naringenin (NG), a naturally occurring citrus flavonone, on the removal of UVB-induced cyclobutane pyrimidine dimers (CPD) from the genome and apoptosis in immortalized p53-mutant human keratinocyte HaCaT cells. The colony-forming assay shows that treatment with NG significantly increases long-term cell survival after UVB irradiation. NG treatment also protects the cells from UVB-induced apoptosis, as indicated by the absence of the 180 base pair DNA ladders and the appearance of sub-G1 peak using agarose gel electrophoresis and flow cytometric analysis, respectively. The UVB-induced poly (ADP-ribose) polymerase-1 (PARP-1) cleavage, caspase activation and Bax/Bcl2 ratio were modulated following NG treatment, indicating an antiapoptotic effect of NG in UVB-damaged cells that occurs at least in part via caspase cascade pathway. Moreover, treatment of UVB-irradiated HaCaT cells with NG enhances the removal of CPD from the genome, as observed by both direct quantitation of CPD in genomic DNA and immuno-localization of the damage within the nuclei. The study provides a molecular basis for the action of NG as a promising natural flavonoid in preventing skin aging and carcinogenesis.