[Risk factors analysis of reversible posterior leukoencephalopathy syndrome in pre-eclampsia or eclampsia gravida]

Objective: To investigate the risk factors of reversible posterior leukoencephalopathy syndrome (RPLS) in pre-eclampsia or eclampsia gravida. Methods: This study was conducted in the Third Affiliated Hospital of Guangzhou Medical University between January 2013 and March 2016. A total of 100 patients who had no severe neurological diseases and were diagnosed pre-eclampsia or eclampsia, and underwent brain MRI were collected retrospectively. They were divided into 2 groups according to the MRI results, the RPLS group (n=49) and the non-RPLS group (n=51). The medical history, clinical symptoms and the results of laboratory examination were analyzed by the logistic regression, in order to explore the risk factors. Results: In single factor analysis, HELLP syndrome, pregnancy associated with other diseases, poor prenatal care, grade 3 hypertension, elevated systolic blood pressure or diastolic blood pressure, elevated WBC, aspartate transaminase (AST), alanine aminotransferase (ALT), uric acid (UA) and lactate dehydrogenase (LDH), decreased platelet (PLT), headache, visual changes, seizures and conscious disturbance were more frequent in the RPLS group than those in the non-RPLS group (all P<0.05). According to the multivariate logistic regression analysis, the elevated WBC (OR=1.291, 95% CI: 1.058-1.575, P=0.012), UA (OR=1.008, 95% CI: 1.001-1.016, P=0.032) and headache (OR=18.260, 95% CI: 3.562-93.607, P=0.000) were the independent risk factors. Conclusions: Maternal history, clinical symptoms and some laboratory examinations might help in the early diagnosis of RPLS in pre-eclampsia or eclampsia gravida. Headache, the elevation of WBC and UA were the most significant factors.

[Noninvasive diagnostic and predictive value in renal transplant recipients with acute rejection by measurement of urine Fractalkine]

Objective: To investigate the relationship between early-stage renal acute rejection(AR) and the level of Fractalkine in urine, explore the diagnostic and noninvasive monitoring value in early stage after transplantation by measurement of urine Fractalkine. Methods: Urine samples were examined from renal transplant patients between January 2006 and October 2009. A total of 155 patients were enrolled, including 49 with biopsy-proved AR, 58 patients with stable renal function and no abnormal histological findings, 10 patients with subclinical rejection in protocol biopsy, 9 patients with biopsy-proven acute tubular necrosis and 29 patients with biopsy-proven chronic allograft nephropathy. Additionally, urine samples were also collected from 40 healthy controls. Fractalkine was measured in urine samples using a commercial human Fractalkine enzyme-linked immunosorbent assay (ELISA) kit. Immunohistochemistry for Fractalkine expression was performed on biopsies from renal transplant patients with AR and non-AR. Results: Forty-nine patients with AR excreted urinary Fractalkine at a significantly higher level than levels in patients with stable renal function and healthy controls[(429.1±56.1)vs (94.6±8.4), (84.5±8.9)ng/mmol creatine, both P<0.001]. Patients with AR excreted urinary Fractalkine at a significantly higher level than levels in patients with acute tubular necrosis and chronic allograft nephropathy[(429.1±56.1)vs(133.0±9.8), (183.0±18.9)ng/mmol creatine, both P<0.001]. Receiver operating characteristic(ROC)curve was constructed to determine the discriminatory power of Fractalkine levels for diagnosis of AR. The area under ROC curve was 0.920(95% CI: 0.875-0.969, P<0.001), which showed that Fractalkine was a suitable marker for the diagnosis of AR. At a cut-off point of 157.5 ng/mmol creatinine, the sensitivity was 83.7% and the specificity was 84.5% (P<0.001). The dynamic level of urinary Fractalkine in AR patients within 3 weeks after transplantation fluctuated above 300 ng/mmol creatine, which is remarkably higher than patients with stable renal function (below 200 ng/mmol creatinine). Conclusions: As a noninvasive monitoring method, Fractalkine in urine may be a new approach for detection of AR as well as useful to predict response to antirejection therapy. It has good sensitivity and specificity. Besides, measurement of Fractalkine in urine is a simple, inexpensive method for the routine clinical monitoring after kidney transplantation.

[Multi-centric clinical study of trial of labor after cesarean section]

OBJECTIVE

To study the feasibility and safety of trial of labor after cesarean section (TOLAC).

METHODS

Retrospective analysis of five medical center of Guangdong province from January 2011 to December 2015 hospitalized delivery information, compare the same scar TOLAC (research group) with the scar pregnancy (control group) pregnancy outcomes, to study the feasibility and safety of TOLAC.

RESULTS

(1) During 2011-2015, total delivery 95 600 cases in five medical center, 13 824 cases of thme with uterine scar pregnancy, including 12 027 cases elective repeat cesarean section and 1 797 cases (13.00%, 1 797/13 824) with scar uterus vaginal trial of labor. Among 1 308 cases of vaginal delivery, the success for trial of labor rate was 72.79% (1 308/1 797). From 2011 to 2015, there were increased rate of pregnancy after cesarean section, which were respectively 10.71%, 13.28%, 14.45%, 15.54% and 16.98%. The will of vaginal birth were rising and the rate were respectively 11.85%, 12.25%, 13.49%, 13.82% and 12.93%. (2) There were 489 (27.21%, 489/1 797) cases of scar uterus maternal emergency cesarean section in the trial of labor, reason for "social factors" require for cesarean delivery have 68 cases, the percentage was 13.91% (68/489), compared with control group (7.18%, 206/2 869), the difference was statistically significant difference (χ(2)=27.356, P=0.000). Doctors diagnosed as "aura uterine rupture" in the labor was 11.86% (58/489), compared with that in control group (1.43%, 41/2 869), the differences were statistically significant difference (χ(2)=1 578.223, P=0.000). (3) The incidence of uterine rupture of the research group (0.74%, 9/1 211) was significantly higher than that of control group (0.01%,2/31 200; χ(2)> 2 000, P=0.000). The incidence of postpartum hemorrhage in research group was 6.94% (84/1 211), compared with that in the control group (3.05%, 951/31 200), there was statistically significant difference (χ(2)=16.328, P=0.000). While, there were no statistical significancefor the labor time limit, birth rate of severe asphyxia and neonatal birth weight average differences between two groups (P>0.05).

CONCLUSIONS

The rate of pregnancy after cesarean section is increasing year by year, and the will of vaginal birth is increasing, while it still are generally low. TOLAC is safe and feasible, but also significantly higher risk, strictly labor monitoring and can proceed fast cesarean delivery in delivery room is an important guarantee of safe delivery.

[Effects of extracellular regulated protein kinases protein and impairment of blood testis barriar stucturein of mice with exposure to decabromodiphenyl ether]

Objective: To study changes in expression of claudin-11 and proteins related to mitogen-activated protein kinase (MAPK) signaling pathways, as well as the ultrastructure of the blood testis barrier (BTB), in male ICR mice exposed to decabromodiphenyl ether (BDE-209). Methods: Fifty-two mice, 4 weeks of age, weighing 15-21 g, were provided with adaptive feeding for 1 week. Mice were randomly divided into 4 groups, named control, low-dose, medium-dose and high-dose groups. The treated groups received BDE-209, by intragastric gavage, at doses, respectively, of 100, 300 and 500 mg/kg. Mice were sacrificed after 6 weeks and organs harvested on ice, weighed and stored at -80 °C. The ultrastructure of testicular tissues was examined by electron microscopy. Western blotting was used to detect proteins related to the MAPK pathway, including p38 mitogen activated protein kinase (p38), phosphorylated p38 (p-p38), extracellular regulated protein kinase 1/2 (ERK1/2) , phosphorylated ERK1/2 (p-ERK1/2) , c-jun N-terminal kinase (JNK), phosphorylated JNK (p-JNK) and the BTB tight junction protein claudin-11. Analyze the difference between each groups. Results: At sacrifice, the body weights in each treated group were compared with those in the control group weighing (41.14 ± 0.60) g. Compared with controls, body weights were significantly different (P<0.05) in the middle dose, at (39.97 ± 0.66) g and high dose, at (39.98± 0.55) g in control group. The coefficients of the testis were significantly lower (P<0.05) in each treated group than in controls, with values of (0.37±0.0)%, (0.31±0.05)% and (0.31±0.04)% for low-dose, medium-dose and high-dose groups, respectively. The epidymus coefficient values were also significantly lower than controls (P<0.05), with values of (0.16±0.06)%, (0.11±0.05)% and (0.07±0.03)%, respectively in the same three dose groups. Electron microscopy ultrastructure showed that, compared with the control group, the testes in the middle and high dose groups had closely connected fractures, cell edema and more vacuoles. Compared with in the control group, levels of p-p38 and p-JNK in testicular tissue were significantly increased (P<0.05). In the control group and in low-, medium- and high-dose groups, the p-p38/p38 ratios were 1.35±0.13, 3.46±0.10, 5.71±0.26 and 4.79±0.21, respectively. The corresponding p-JNK/JNK ratios were 2.07±0.0, 4.77±0.18, 3.63±0.06 and 4.85±0.15. Claudin-11 levels were significantly lower (P<0.05) than control values in each dosed group. The corresponding values in control, low-dose, medium-dose and high-dose groups were 8.33±0.36, 2.06±0.27, 3.37±0.27 and 1.55±0.19, respectively. Conclusion: BDE-209 increased expression of proteins in the MAPK pathway and decreased expression of the BTB tight junction protein claudin-11 in testicular tissue. It also caused ultrastructural damage to the Sertoli cell BTB tight junctions. This suggested that BDE-209 might damage Sertoli cells BTB through effects on the MAPK pathway.

Clinical significance of coryneform Gram-positive rods from blood identified by MALDI-TOF mass spectrometry and their susceptibility profiles - a retrospective chart review

With the advent of matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS), most Gram-positive rods (GPRs) are readily identified; however, their clinical relevance in blood cultures remains unclear. Herein, we assessed the clinical significance of GPRs isolated from blood and identified in the era of MALDI-TOF MS. A retrospective chart review of patients presenting to the Mayo Clinic, Rochester, MN, from January 1, 2013, to October 13, 2015, was performed. Any episode of a positive blood culture for a GPR was included. We assessed the number of bottles positive for a given isolate, time to positivity of blood cultures, patient age, medical history, interpretation of culture results by the healthcare team and whether infectious diseases consultation was obtained. We also evaluated the susceptibility profiles of a larger collection of GPRs tested in the clinical microbiology laboratory of the Mayo Clinic, Rochester, MN from January 1, 2013, to October 31, 2015. There were a total of 246 GPRs isolated from the blood of 181 patients during the study period. 56% (n = 101) were deemed contaminants by the healthcare team and were not treated; 33% (n = 59) were clinically determined to represent true bacteremia and were treated; and 8% (n = 14) were considered of uncertain significance, with patients prescribed treatment regardless. Patient characteristics associated with an isolate being treated on univariate analysis included younger age (P = 0.02), identification to the species level (P = 0.02), higher number of positive blood culture sets (P < 0.0001), lower time to positivity (P < 0.0001), immunosuppression (P = 0.03), and recommendation made by an infectious disease consultant (P = 0.0005). On multivariable analysis, infectious diseases consultation (P = 0.03), higher number of positive blood culture sets (P = 0.0005) and lower time to positivity (P = 0.03) were associated with an isolate being treated. 100, 83, 48 and 34% of GPRs were susceptible to vancomycin, meropenem, penicillin and ceftriaxone, respectively.

Does cumulative prostate cancer length (CCL) in prostate biopsies improve prediction of clinically insignificant cancer at radical prostatectomy in patients eligible for active surveillance?

OBJECTIVES

To evaluate if cumulative prostate cancer length (CCL) on prostate needle biopsy divided by the number of biopsy cores (CCL/core) could improve prediction of insignificant cancer on radical prostatectomy (RP) in patients with prostate cancer eligible for active surveillance (AS).

PATIENTS AND METHODS

Patients diagnosed with prostate cancer on extended (≥10 cores) biopsy with an initial prostate-specific antigen (iPSA) level of <15 ng/mL, clinical stage (cT) ≤ 2a, and highest biopsy Gleason score 3 + 3 = 6 or 3 + 4 = 7 with <3 positive cores who underwent RP were included in the study. The CCL/core and presence of insignificant cancer (organ-confined, volume <0.5 mL, Gleason score at RP ≤6) were recorded. pT2 prostate cancer with RP Gleason score ≤3 + 4 = 7 and volume <0.5 mL were categorised as low-tumour-volume organ-confined disease (LV-OCD).

RESULTS

In all, 221 patients met the inclusion criteria: the mean age was 59 years and the median iPSA level was 4.5 ng/mL. The clinical stage was cT1 in 86% of patients; biopsy Gleason score was 3 + 3 = 6 in 67% (group 1) and 3 + 4 = 7 in 33% of patients (group 2). The maximum percentage of biopsy core involvement was <50 in 85%; the median CCL/core was 0.15 mm. Insignificant cancer was found in 27% and LV-OCD in 44% of patients. Group 2 was associated with higher number of positive cores, maximum percentage core involvement, total prostate cancer length, and CCL/core. Group 1 was more likely to have insignificant cancer (39%) or LV-OCD (54%) than group 2 (3% and 23%, respectively). Group 2 had significantly higher RP Gleason score and pathological stage. Univariate analysis of group 1 showed that the iPSA level, maximum percentage core involvement, prostate cancer length, and CCL/core were all significantly associated with insignificant cancer and LV-OCD. For group 2, the number of positive cores (1 vs 2) was also significantly associated with LV-OCD. On multivariate logistic regression analysis, maximum percentage core involvement of <50, and number of positive cores (1 vs 2) were independent predictors of insignificant cancer in group 1; biopsy Gleason score, maximum percentage core involvement of <50 and prostate cancer length of <3 mm or CCL/core of <0.2 mm were all independent predictors of LV-OCD in the whole population. The maximum percentage of core involvement of <50 and prostate cancer length of <3 mm or CCL/core of <0.2 mm were also independent predictors of LV-OCD in group 1 patients.

CONCLUSION

In patients eligible for AS, a CCL/core of <0.20 mm was significantly associated with insignificant cancer and LV-OCD. However, when parameters of cancer burden were considered, CCL/core did not independently add any additional value for predicting insignificant cancer in patients with biopsy Gleason score 6. The CCL/core was an independent predictor of LV-OCD in the whole population and in group 1 patients, although the model including prostate cancer length showed slightly higher area under the receiver operating characteristic curve.

Lack of association between Human Oxoguanine Glycosylase 1 (hOGG1) S326C polymorphism and the risk of gastric cancer: a meta-analysis

Results from published studies on the association of Human Oxoguanine Glycosylase 1 (hOGG1) S326C genetic polymorphism with the risk of gastric cancer are inconsistent. We performed a meta-analysis to summarize the possible association. Eleven case-control studies including 2168 cases and 4058 controls were identified from electronic databases (Pubmed, Elsevier Science Direct, Chinese National Knowledge Infrastructure (CNKI), Chinese Biomedical Literature Database (CBM), and the Chinese database, Wanfang). No significant association between hOGG1 S326C genetic polymorphism and risk of gastric cancer was observed in the overall analysis. In the stratified analysis based on ethnicity, still no significant association was observed in Europeans, Asians, or Brazilians. This meta-analysis provided evidence that hOGG1 S326C genetic polymorphism was not associated with increased risk of gastric cancer. However, additional studies with large sample size and better study designs are warranted to verify our finding.

Indium-rich InGaN epitaxial layers grown pseudomorphically on a nano-sculpted InGaN template

Indium-rich InGaN epitaxial layers with a p-i-n structure were grown pseudomorphically on a strain-relaxed InGaN template to reduce structural strain induced by lattice mismatch. We applied a nano-sculpting process to improve the crystal quality of the strain-relaxed InGaN template. The results show that the nano-sculpting process can suppress effectively the threading dislocation generation and improves significantly the I-V characteristic of the InGaN p-i-n structure. This InGaN template technique with nano-sculpting process shows great potential for future applications in indium-rich InGaN optic-electron devices.

Role of SUMO:SIM-mediated protein-protein interaction in non-homologous end joining

Although post-translational modifications by the small ubiquitin-like modifiers (SUMO) are known to be important in DNA damage response, it is unclear whether they have a role in double-strand break (DSB) repair by non-homologous end joining (NHEJ). Here, we analyzed various DSB repair pathways upon inhibition of SUMO-mediated protein-protein interactions using peptides that contain the SUMO-interaction motif (SIM) and discriminate between mono- and SUMO-chain modifications. The SIM peptides specifically inhibit NHEJ as shown by in vivo repair assays and radio-sensitivity of cell lines deficient in different DSB repair pathways. Furthermore, mono-SUMO, instead of SUMO-chain, modifications appear to be involved in NHEJ. Immunoprecipitation experiments also showed that the SIM peptide interacted with SUMOylated Ku70 after radiation. This study is the first to show an important role for SUMO:SIM-mediated protein-protein interactions in NHEJ, and provides a mechanistic basis for the role of SIM peptide in sensitizing genotoxic stress of cancer cells.

Biological dose estimation of UVA laser microirradiation utilizing charged particle-induced protein foci

The induction of localized DNA damage within a discrete nuclear volume is an important tool in DNA repair studies. Both charged particle irradiation and laser microirradiation (LMI) systems allow for such a localized damage induction, but the results obtained are difficult to compare, as the delivered laser dose cannot be measured directly. Therefore, we revisited the idea of a biological dosimetry based on the microscopic evaluation of irradiation-induced Replication Protein A (RPA) foci numbers. Considering that local dose deposition is characteristic for both LMI and charged particles, we took advantage of the defined dosimetry of particle irradiation to estimate the locally applied laser dose equivalent. Within the irradiated nuclear sub-volumes, the doses were in the range of several hundreds of Gray. However, local dose estimation is limited by the saturation of the RPA foci numbers with increasing particle doses. Even high-resolution 4Pi microscopy did not abrogate saturation as it was not able to resolve single lesions within individual RPA foci. Nevertheless, 4Pi microscopy revealed multiple and distinct 53BP1- and gamma H2AX-stained substructures within the lesion flanking chromatin domains. Monitoring the local recruitment of the telomere repeat-binding factors TRF1 and TRF2 showed that both proteins accumulated at damage sites after UVA-LMI but not after densely ionizing charged particle irradiation. Hence, our results indicate that the local dose delivered by UVA-LMI is extremely high and cannot be accurately translated into an equivalent ionizing radiation dose, despite the sophisticated techniques used in this study.

Role of homologous recombination in the alpha-particle-induced bystander effect for sister chromatid exchanges and chromosomal aberrations

The bystander effect for sister chromatid exchanges (SCEs) and chromosomal aberrations was examined in hamster cell lines deficient in either DNA-PKcs (V3 cells, deficient in nonhomologous end joining, NHEJ) or RAD51C (irs3 cells, deficient in homologous recombination, HR). Cells synchronized in G0/G1 phase were irradiated with very low fluences of alpha particles such that < 1% of the nuclei were traversed by an alpha particle. Wild-type cells showed a prominent bystander response for SCE induction; an even greater effect was observed in V3 cells. On the other hand, no significant induction of SCE was observed in the irs3 RAD51C-deficient bystander cells irradiated at various stages in the cell cycle. Whereas a marked bystander effect for chromosomal aberrations occurred in V3 cells, the induction of chromosomal aberrations in irs3 bystander cells was minimal and similar to that of wild-type cells. Based on these findings, we hypothesize that HR is essential for the induction of SCE in bystander cells; however, HR is unable to repair the DNA damage induced in NHEJ-deficient bystander cells that leads to either SCE or chromosomal aberrations.

DNA-PKcs is critical for telomere capping

The DNA-dependent protein kinase catalytic subunit (DNA-PKcs) is critical for DNA repair via the nonhomologous end joining pathway. Previously, it was reported that bone marrow cells and spontaneously transformed fibroblasts from SCID (severe combined immunodeficiency) mice have defects in telomere maintenance. The genetically defective SCID mouse arose spontaneously from its parental strain CB17. One known genomic alteration in SCID mice is a truncation of the extreme carboxyl terminus of DNA-PKcs, but other as yet unidentified alterations may also exist. We have used a defined system, the DNA-PKcs knockout mouse, to investigate specifically the role DNA-PKcs specifically plays in telomere maintenance. We report that primary mouse embryonic fibroblasts (MEFs) and primary cultured kidney cells from 6-8 month-old DNA-PKcs-deficient mice accumulate a large number of telomere fusions, yet still retain wild-type telomere length. Thus, the phenotype of this defect separates the two-telomere related phenotypes, capping, and length maintenance. DNA-PKcs-deficient MEFs also exhibit elevated levels of chromosome fragments and breaks, which correlate with increased telomere fusions. Based on the high levels of telomere fusions observed in DNA-PKcs deficient cells, we conclude that DNA-PKcs plays an important capping role at the mammalian telomere.

Differential gene expression in a DNA double-strand-break repair mutant XRS-5 defective in Ku80: analysis by cDNA microarray

The ability of cells to rejoin DNA double-strand breaks (DSBs) usually correlates with their radiosensitivity. This correlation has been demonstrated in radiosensitive cells, including the Chinese hamster ovary mutant XRS-5. XRS-5 is defective in a DNA end-binding protein, Ku80, which is a component of a DNA-dependent protein kinase complex used for joining strand breaks. However, Ku80-deficient cells are known to be retarded in cell proliferation and growth as well as other yet to be identified defects. Using custom-made 600-gene cDNA microarray filters, we found differential gene expressions between the wild-type and XRS-5 cells. Defective Ku80 apparently affects the expression of several repair genes, including topoisomerase-I and -IIA, ERCC5, MLH1, and ATM. In contrast, other DNA repair-associated genes, such as GADD45A, EGR1 MDM2 and p53, were not affected. In addition, for large numbers of growth-associated genes, such as cyclins and clks, the growth factors and cytokines were also affected. Down-regulated expression was also found in several categories of seemingly unrelated genes, including apoptosis, angiogenesis, kinase and signaling, phosphatase, stress protein, proto-oncogenes and tumor suppressors, transcription and translation factors. A RT-PCR analysis confirmed that the XRS-5 cells used were defective in Ku80 expression. The diversified groups of genes being affected could mean that Ku80, a multi-functional DNA-binding protein, not only affects DNA repair, but is also involved in transcription regulation. Our data, taken together, indicate that there are specific genes being modulated in Ku80- deficient cells, and that some of the DNA repair pathways and other biological functions are apparently linked, suggesting that a defect in one gene could have global effects on many other processes.

ATM phosphorylates histone H2AX in response to DNA double-strand breaks

A very early step in the response of mammalian cells to DNA double-strand breaks is the phosphorylation of histone H2AX at serine 139 at the sites of DNA damage. Although the phosphatidylinositol 3-kinases, DNA-PK (DNA-dependent protein kinase), ATM (ataxia telangiectasia mutated), and ATR (ATM and Rad3-related), have all been implicated in H2AX phosphorylation, the specific kinase involved has not yet been identified. To definitively identify the specific kinase(s) that phosphorylates H2AX in vivo, we have utilized DNA-PKcs-/- and Atm-/- cell lines and mouse embryonic fibroblasts. We find that H2AX phosphorylation and nuclear focus formation are normal in DNA-PKcs-/- cells and severely compromised in Atm-/- cells. We also find that ATM can phosphorylate H2AX in vitro and that ectopic expression of ATM in Atm-/- fibroblasts restores H2AX phosphorylation in vivo. The minimal H2AX phosphorylation in Atm-/- fibroblasts can be abolished by low concentrations of wortmannin suggesting that DNA-PK, rather than ATR, is responsible for low levels of H2AX phosphorylation in the absence of ATM. Our results clearly establish ATM as the major kinase involved in the phosphorylation of H2AX and suggest that ATM is one of the earliest kinases to be activated in the cellular response to double-strand breaks.

The three-dimensional structure of the C-terminal DNA-binding domain of human Ku70

The proteins Ku70 (69.8 kDa) and Ku80 (82.7 kDa) form a heterodimeric complex that is an essential component of the nonhomologous end joining DNA double-strand break repair pathway in mammalian cells. Interaction of Ku with DNA is central for the functions of Ku. Ku70, which is mainly responsible for the DNA binding activity of the Ku heterodimer, contains two DNA-binding domains. We have solved the solution structure of the Ku80-independent DNA-binding domain of Ku70 encompassing residues 536-609 using nuclear magnetic resonance spectroscopy. Residues 536-560 are highly flexible and have a random structure but form specific interactions with DNA. Residues 561-609 of Ku70 form a well defined structure with 3 alpha-helices and also interact with DNA. The three-dimensional structure indicates that all conserved hydrophobic residues are in the hydrophobic core and therefore may be important for structural integrity. Most of the conserved positively charged residues are likely to be critical for DNA recognition. The C-terminal DNA-binding domain of Ku70 contains a helix-extended strand-helix motif, which occurs in other nucleic acid-binding proteins and may represent a common nucleic acid binding motif.

Werner syndrome protein is regulated and phosphorylated by DNA-dependent protein kinase

DNA double-strand breaks (DSBs) are a highly mutagenic and potentially lethal damage that occurs in all organisms. Mammalian cells repair DSBs by homologous recombination and non-homologous end joining, the latter requiring DNA-dependent protein kinase (DNA-PK). Werner syndrome is a disorder characterized by genomic instability, aging pathologies and defective WRN, a RecQ-like helicase with exonuclease activity. We show that WRN interacts directly with the catalytic subunit of DNA-PK (DNA-PK(CS)), which inhibits both the helicase and exonuclease activities of WRN. In addition we show that WRN forms a stable complex on DNA with DNA-PK(CS) and the DNA binding subunit Ku. This assembly reverses WRN enzymatic inhibition. Finally, we show that WRN is phosphorylated in vitro by DNA-PK and requires DNA-PK for phosphorylation in vivo, and that cells deficient in WRN are mildly sensitive to ionizing radiation. These data suggest that DNA-PK and WRN may function together in DNA metabolism and implicate WRN function in non-homologous end joining.

Strand-specific postreplicative processing of mammalian telomeres

Telomeres are specialized nucleoprotein structures that stabilize the ends of linear eukaryotic chromosomes. In mammalian cells, abrogation of telomeric repeat binding factor TRF2 or DNA-dependent protein kinase (DNA-PK) activity causes end-to-end chromosomal fusion, thus establishing an essential role for these proteins in telomere function. Here we show that TRF2-mediated end-capping occurs after telomere replication. The postreplicative requirement for TRF2 and DNA-PKcs, the catalytic subunit of DNA-PK, is confined to only half of the telomeres, namely, those that were produced by leading-strand DNA synthesis. These results demonstrate a crucial difference in postreplicative processing of telomeres that is linked to their mode of replication.

[Purification of vancomycin by using magnetic affinity technique]

A new kind of magnetic affinity microspheres (MAMS), whose ligand is D-Ala-D-Ala, was prepared using agarose as matrix. By using this new MAMS vancomycin was purified directly from crude fermentation liquor with only one step. The purity and the mass recovery of vancomycin measured by reverse-phase HPLC were 97% and 87%, respectively. The characteristic of this method was simpler, faster, cheaper and more effective than that of currently used ones.

A translational couch technique for total body irradiation

We have constructed a computer controlled translational couch to administer total body irradiation reproducibly and safely. The system has replaced the previous stationary anterior-posterior technique in our institution and 30 plus patients have been treated with it so far. In this technique, patients comfortably lie on a couch in supine and prone positions and are transported slowly through a narrow beam with the gantry in an upright position. Dose to the patient is determined by the couch velocity that is calculated based on physical parameters such as patient's dimensions, beam geometry, and machine dose rate. In our design, the couch velocity is continuously updated to compensate for machine dose rate fluctuations. The translational couch technique provides better dose uniformity within the patient compared to fixed beam techniques, and allows a more precise shielding block placement for organs at risk. At the same time, it presents a special challenge for dosimetry calculations. A dosimetry parameter is introduced that converts the moving beam output to the fixed beam output factor. Based on this factor, a simple dosimetry calculation method has been developed that takes advantage of conventional dosimetry parameters, eliminating extensive dosimetry measurements. Multiple point dose measurements within a phantom confirmed the validity of the calculation method.

A possible role of Ku in mediating sequential repair of closely opposed lesions

One of the hallmarks of ionizing radiation exposure is the formation of clustered damage that includes closely opposed lesions. We show that the Ku70/80 complex (Ku) has a role in the repair of closely opposed lesions in DNA. DNA containing a dihydrouracil (DHU) close to an opposing single strand break was used as a model substrate. It was found that Ku has no effect on the enzymatic activity of human endonuclease III when the substrate DNA contains only DHU. However, with DNA containing a DHU that is closely opposed to a single strand break, Ku inhibited the nicking activity of human endonuclease III as well as the amount of free double strand breaks induced by the enzyme. The inhibition on the formation of a free double strand break by Ku was found to be much greater than the inhibition of human endonuclease III-nicking activity by Ku. Furthermore, there was a concomitant increase in the formation of Ku-DNA complexes when endonuclease III was present. Similar results were also observed with Escherichia coli endonuclease III. These results suggest that Ku reduces the formation of endonuclease III-induced free double strand breaks by sequestering the double strand breaks formed as a Ku-DNA complex. In doing so, Ku helps to avoid the formation of the intermediary free double strand breaks, possibly helping to reduce the mutagenic event that might result from the misjoining of frank double strand breaks.

DNA-PKcs is required for activation of innate immunity by immunostimulatory DNA

Bacterial DNA and related synthetic immunostimulatory oligodeoxyribonucleotides (ISS-ODN) stimulate innate immunity. However, the molecular recognition mechanism that initiates signaling in response to bacterial DNA and ISS-ODN has not been identified. Herein, we demonstrate that administration of bacterial DNA and ISS-ODN to mice lacking the catalytic subunit of DNA-PK (DNA-PKcs) and in vitro stimulation of BMDM from these mice result in defective induction of IL-6 and IL-12. Further analysis using BMDM of IKKbeta(-/-) revealed that both DNA-PKcs and IKKbeta are essential for normal cytokine production in response to ISS-ODN or bacterial DNA. ISS-ODN and bacterial DNA activate DNA-PK, which in turn contributes to activation of IKK and NF-kappaB. These results reveal a novel role of DNA-PKcs in innate immune responses and a link between DNA repair and innate immunity.

Ku acts in a unique way at the mammalian telomere to prevent end joining

Telomeres are specialized DNA/protein structures that act as protective caps to prevent end fusion events and to distinguish the chromosome ends from double-strand breaks. We report that TRF1 and Ku form a complex at the telomere. The Ku and TRF1 complex is a specific high-affinity interaction, as demonstrated by several in vitro methods, and exists in human cells as determined by coimmunoprecipitation experiments. Ku does not bind telomeric DNA directly but localizes to telomeric repeats via its interaction with TRF1. Primary mouse embryonic fibroblasts that are deficient for Ku80 accumulated a large percentage of telomere fusions, establishing that Ku plays a critical role in telomere capping in mammalian cells. We propose that Ku localizes to internal regions of the telomere via a high-affinity interaction with TRF1. Therefore, Ku acts in a unique way at the telomere to prevent end joining.

Signal joint formation is also impaired in DNA-dependent protein kinase catalytic subunit knockout cells

The effort to elucidate the mechanism of V(D)J recombination has given rise to a dispute as to whether DNA-dependent protein kinase catalytic subunit (DNA-PKcs) contributes to signal joint formation (sjf). Observations reported to date are confusing. Analyses using DNA-PKcs-deficient cells could not conclude the requirement of DNA-PKcs for sjf, because sjf can be formed by end-joining activities which are diverse among cells other than those participating in V(D)J recombination. Here, we observed V(D)J recombination in DNA-PKcs knockout cells and showed that both signal and coding joint formation were clearly impaired in the cells. Subsequently, to directly demonstrate the requirement of DNA-PKcs for sjf, we introduced full-length cDNA of DNA-PKcs into the knockout cells. Furthermore, several mutant DNA-PKcs cDNA constructs designed from mutant cell lines (irs-20, V3, murine scid, and SX9) were also introduced into the cells to obtain further evidence indicating the involvement of DNA-PKcs in sjf. We found as a result that the full-length cDNA complemented the aberrant sjf and that the mutant cDNAs constructs also partially complemented it. Lastly, we looked at whether the kinase activity of DNA-PKcs is necessary for sjf and, as a result, demonstrated a close relationship between them. Our observations clearly indicate that the DNA-PKcs controls not only coding joint formation but also the sjf in V(D)J recombination through its kinase activity.

Evidence for simultaneous protein interactions between human Rad51 paralogs

In yeast, the Rad51-related proteins include Rad55 and Rad57, which form a heterodimer that interacts with Rad51. Five human Rad51 paralogs have been identified (XRCC2, XRCC3, Rad51B/Rad51L1, Rad51C/Rad51L2, and Rad51D/Rad51L3), and each interacts with one or more of the others. Previously we reported that HsRad51 interacts with XRCC3, and Rad51C interacts with XRCC3, Rad51B, and HsRad51. Here we report that in the yeast two-hybrid system, Rad51D interacts with XRCC2 and Rad51C. No other interactions, including self-interactions, were found, indicating that the observed interactions are specific. The yeast Rad51 interacts with human Rad51 and XRCC3, suggesting Rad51 conservation since the human yeast divergence. Data from yeast three-hybrid experiments indicate that a number of the pairs of interactions between human Rad51 paralogs can occur simultaneously. For example, Rad51B expression enhances the binding of Rad51C to XRCC3 and to HsRad51D, and Rad51C expression allows the indirect interaction of Rad51B with Rad51D. Experiments using 6xHis-tagged proteins in the baculovirus system confirm several of our yeast results, including Rad51B interaction with Rad51D only when Rad51C is simultaneously expressed and Rad51C interaction with XRCC2 only when Rad51D is present. These results suggest that these proteins may participate in one complex or multiple smaller ones.

DNA interstrand cross-links induce futile repair synthesis in mammalian cell extracts

DNA interstrand cross-links are induced by many carcinogens and anticancer drugs. It was previously shown that mammalian DNA excision repair nuclease makes dual incisions 5' to the cross-linked base of a psoralen cross-link, generating a gap of 22 to 28 nucleotides adjacent to the cross-link. We wished to find the fates of the gap and the cross-link in this complex structure under conditions conducive to repair synthesis, using cell extracts from wild-type and cross-linker-sensitive mutant cell lines. We found that the extracts from both types of strains filled in the gap but were severely defective in ligating the resulting nick and incapable of removing the cross-link. The net result was a futile damage-induced DNA synthesis which converted a gap into a nick without removing the damage. In addition, in this study, we showed that the structure-specific endonuclease, the XPF-ERCC1 heterodimer, acted as a 3'-to-5' exonuclease on cross-linked DNA in the presence of RPA. Collectively, these observations shed some light on the cellular processing of DNA cross-links and reveal that cross-links induce a futile DNA synthesis cycle that may constitute a signal for specific cellular responses to cross-linked DNA.