mitomycin

丝裂霉素
  • 文章类型: Journal Article
    比较接受加速角膜交联(A-CXL)和无丝裂霉素C(MMC)的选择性波前引导的经上皮光折射角膜切除术(WG-tranPRK)与接受A-CXL的患者的雾度和屈光结果。
    这项前瞻性研究分析了2018年10月至2022年10月患有进行性圆锥角膜的95只眼睛(86例患者)。第一组行CXL联合角膜或眼部WG-transPRK(CXL+PRK,n=52),瞄准高阶像差(HOAs)。第二个仅接受CXL(n=43),两者都遵循SCHWINDAmaris激光平台(SCHWINDeye-tech-solutions)上没有MMC的相同加速CXL协议。基线和术后评估(1、3、6和12个月)包括未矫正(UDVA)和矫正(CDVA)远距视力,明显的折射,断层摄影术,角膜HOAs,和光学相干断层扫描(OCT)扫描。专利的机器学习算法以灰度单位客观地检测和量化OCT扫描上的基质雾度。
    在两组中,角膜前雾霾反射率和上皮下雾霾在术后3个月达到峰值,然后在6个月和12个月时逐渐下降。在任何时间点,组之间的雾度没有差异。到12个月,CDVA在CXL+PRK组增加2.5行(P<.001),在CXL组增加0.7行(P=.10),最大角膜曲率从51.70±5.10降至47.90±7.90屈光度(D)(CXLPRK组)(P<.001),从51.20±5.10降至50.30±4.60D(CXL组)(P=.004)。两组角膜HOA均下降,但CXLPRK组下降更多。
    与单独的A-CXL相比,在没有MMC的情况下将CXL与WG-tranPRK组合不会导致雾度增加。这种组合方法在视觉上实现了更大的改进,地形,和像差参数。[JRefractSurg.2024;40(9):e583-e594。].
    UNASSIGNED: To compare haze and refractive outcomes in patients undergoing combined accelerated corneal cross-linking (A-CXL) and selective wavefront-guided transepithelial photorefractive keratectomy (WG-transPRK) without mitomycin C (MMC) versus those undergoing A-CXL.
    UNASSIGNED: This prospective study analyzed 95 eyes (86 patients) with progressive keratoconus from October 2018 to October 2022. The first group underwent CXL combined with corneal or ocular WG-transPRK (CXL+PRK, n = 52), targeting higher order aberrations (HOAs). The second underwent CXL only (n = 43), both following the same accelerated CXL protocol without MMC on the SCHWIND Amaris laser platform (SCHWIND eye-tech-solutions). Baseline and postoperative evaluations (1, 3, 6, and 12 months) included uncorrected (UDVA) and corrected (CDVA) distance visual acuity, manifest refraction, tomography, corneal HOAs, and optical coherence tomography (OCT) scans. A patented machine learning algorithm objectively detected and quantified stromal haze on OCT scans in grayscale units.
    UNASSIGNED: In both groups, anterior corneal haze reflectivity and subepithelial haze peaked at 3 months postoperatively, then progressively decreased at 6 and 12 months. Haze did not differ between groups at any time point. By 12 months, CDVA increased by 2.5 lines in the CXL+PRK group (P < .001) and by 0.7 lines in the CXL group (P = .10), and maximum keratometry decreased from 51.70 ± 5.10 to 47.90 ± 7.90 diopters (D) (CXL+PRK group) (P < .001) and from 51.20 ± 5.10 to 50.30 ± 4.60 D (CXL group) (P = .004). Corneal HOAs decreased in both groups but more in the CXL+PRK group.
    UNASSIGNED: Combining CXL with WG-transPRK without MMC does not result in increased haze when compared to A-CXL alone. This combined approach achieves greater improvements in visual, topographic, and aberrometric parameters. [J Refract Surg. 2024;40(9):e583-e594.].
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  • 文章类型: Journal Article
    目的:小梁切除术,青光眼的初级手术治疗,通常使用丝裂霉素C(MMC)来减少瘢痕形成并改善手术效果。然而,MMC的最优应用方法,无论是注射还是海绵,仍然是一个辩论的主题。这项荟萃分析旨在比较可注射和海绵基MMC在疗效和安全性方面的应用。关注青光眼患者的各种临床结果。
    方法:Scopus的全面文献检索,MEDLINE,EMBASE,奥维德,中国生物医学文献数据库,中国国家知识基础设施,和Cochrane图书馆是针对符合条件的研究进行的,这些研究报告了青光眼患者在小梁切除术期间通过注射或海绵应用MMC的数据.感兴趣的结果包括眼内压(IOP)降低,气泡外观分级(高度,范围,血管分布),使用抗青光眼药物,和完全成功率,合格的成功,和失败。数据报告为加权平均差(WMD)或比值比(OR)和置信区间(CI)。采用Tau2的DerSimonian-Laird估计的随机效应逆方差模型,在必要时应用连续性校正。
    结果:共纳入15项研究,1276名参与者。荟萃分析显示,通过MMC注射和海绵应用治疗的患者在降低IOP方面没有显着差异(WMD=-0.434)。在高度(WMD=-0.170)和程度(WMD=0.174)的气泡外观评分方面观察到显着差异,具有很大的异质性。注射组抗青光眼药物的使用明显较低(WMD=-0.274)。然而,完全成功率没有显着差异,合格的成功,和失败。该研究显示了各种结果的中度到高度异质性。
    结论:这项荟萃分析表明,虽然在小梁切除术期间注射和海绵方法应用MMC对降低眼压同样有效,它们对气泡形态和术后药物需求的影响不同。研究结果强调了青光眼手术中个性化治疗方法的必要性,考虑到每个患者的具体需求和特征。
    OBJECTIVE: Trabeculectomy, a primary surgical treatment for glaucoma, often employs mitomycin C (MMC) to reduce scar formation and improve surgical outcomes. However, the optimal application method of MMC, whether by injection or sponge, remains a subject of debate. This meta-analysis aims to compare injectable and sponge-based MMC application in terms of efficacy and safety, focusing on various clinical outcomes in glaucoma patients.
    METHODS: A comprehensive literature search of Scopus, MEDLINE, EMBASE, Ovid, Chinese biomedical literature database, China National Knowledge Infrastructure, and Cochrane Library was done for eligible studies that report data of glaucoma patients who were administered MMC by injection or sponge application during trabeculectomy. Outcomes of interest included intraocular pressure (IOP) reduction, bleb appearance grading (height, extent, vascularity), use of anti-glaucoma medications, and rates of complete success, qualified success, and failure. Data were reported as weighted mean differences (WMD) or odds ratios (OR) with confidence intervals (CI). The random-effects inverse-variance model with DerSimonian-Laird estimate of tau2 was employed, with continuity correction applied where necessary.
    RESULTS: A total of 15 studies with 1276 participants were included. The meta-analysis revealed no significant difference in IOP reduction between patients treated by MMC injection and sponge application (WMD = - 0.434). Significant differences were observed in bleb appearance grading scores for height (WMD = - 0.170) and extent (WMD = 0.174), with substantial heterogeneity. The use of anti-glaucoma medications was significantly lower in the injection group (WMD = - 0.274). However, there were no significant differences in the rates of complete success, qualified success, and failure. The study demonstrated moderate to high heterogeneity across various outcomes.
    CONCLUSIONS: This meta-analysis indicated that while both injection and sponge methods of MMC application during trabeculectomy were equally effective for IOP reduction, they differ in their impact on bleb morphology and postoperative medication requirement. The findings highlight the need for individualized treatment approaches in glaucoma surgery, taking into account the specific needs and characteristics of each patient.
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  • 文章类型: Journal Article
    毛乳头细胞(DPC)表现出自我恢复能力,这可能与头发生长有关。因此,我们测试了DPC是否受到暂时的生长抑制压力(睾酮,17β-雌二醇,丝裂霉素C,或营养不良)治疗表现出自我恢复行为,可以激活毛囊生长,并检查了细胞增殖能力和基因表达的变化。鉴定相关蛋白,并使用小鼠模型检查其与毛发周期的关系。恢复期DPC(即,从加载后第3天开始)进行微阵列分析,以检测每种应激治疗常见的遗传变异。恢复期DPCs与外根鞘细胞(ORSCs)共培养证实促进ORSC增殖,提示毛囊生长的激活是通过信号转导促进的。几丁质酶3样1(CHI3L1)和C-X-C基序趋化因子5(CXCL5)显示出促进ORSC增殖的作用。在小鼠毛发周期的每个阶段测量皮肤中的蛋白质含量表明,CHI3L1和CXCL5的分泌在生长期过渡后立即增加。在用睾酮或17β-雌二醇治疗的脱发小鼠模型中,CHI3L1和CXCL5的分泌在处理过的皮肤中低于未处理的皮肤。我们的结果表明,恢复状态DPC分泌的CHI3L1和CXCL5促进头发生长。
    Dermal papilla cells (DPCs) exhibit self-recovery ability, which may be involved in hair growth. Therefore, we tested whether DPCs subjected to temporary growth-inhibiting stress (testosterone, 17β-estradiol, mitomycin C, or undernutrition) treatments exhibit self-recovery behavior that can activate hair follicle growth, and examined the changes in cell proliferation capacity and gene expression. Related proteins were identified and their relationships with the hair cycle was examined using a mouse model. Recovery-period DPCs (i.e., from day 3 after loading) were subjected to microarray analysis to detect genetic variations common to each stress treatment. Co-culture of recovery-period DPCs and outer root sheath cells (ORSCs) confirmed the promotion of ORSC proliferation, suggesting that the activation of hair follicle growth is promoted via signal transduction. Chitinase 3-like 1 (CHI3L1) and C-X-C motif chemokine 5 (CXCL5) exhibited ORSC proliferation-promoting effects. Measurement of protein content in the skin during each phase of the hair cycle in mice revealed that CHI3L1 and CXCL5 secretion increased immediately after anagen transition. In a hair-loss mouse model treated with testosterone or 17β-estradiol, CHI3L1 and CXCL5 secretion was lower in treated telogen skin than in untreated skin. Our results suggest that CHI3L1 and CXCL5 secreted by recovery-state DPCs promote hair growth.
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  • 文章类型: Journal Article
    丝裂霉素是链霉菌产生的一类天然分子,具有很强的抗菌和抗肿瘤活性。MitM是一种关键的后mitosane修饰酶,参与丝裂霉素的生物合成。先前建议该蛋白质催化丝裂霉素A和丝裂霉素中间体9a-去甲基-丝裂霉素A的氮丙啶甲基化作为N-甲基转移酶。MitM识别辅因子S-腺苷-1-甲硫氨酸(SAM)和底物丝裂霉素A的结构基础未知。这里,我们确定了apo-MitM和MitM-丝裂霉素A-S-腺苷同型半胱氨酸(SAH)三元配合物的晶体结构,分辨率分别为2.23和2.80。分别。我们发现MitM采用I类SAM依赖性甲基转移酶折叠并在溶液中形成同源二聚体。参与形成活性口袋的一系列残基的构象变化有助于MitM结合SAH和丝裂霉素A。28ALGAASLGE36循环变化最显著。当丝裂霉素A结合时,这个环的弯曲方向是相反的,将活动站点的入口从开放更改为关闭。这项研究提供了有关MitM参与丝裂霉素生物合成的后mitosane阶段的结构见解,并为甲基转移酶的工程提供了模板。
    Mitomycins make up a class of natural molecules produced by Streptomyces with strong antibacterial and antitumor activities. MitM is a key postmitosane modification enzyme involved in mitomycin biosynthesis in Streptomyces caespitosus. This protein was previously suggested to catalyze the aziridinium methylation of mitomycin A and the mitomycin intermediate 9a-demethyl-mitomycin A as an N-methyltransferase. The structural basis for MitM to recognize cofactor S-adenosyl-l-methionine (SAM) and substrate mitomycin A is unknown. Here, we determined the crystal structures of apo-MitM and MitM-mitomycin A-S-adenosylhomocysteine (SAH) ternary complexes with resolutions of 2.23 and 2.80 Å, respectively. We found that MitM adopts a class I SAM-dependent methyltransferase fold and forms a homodimer in solution. Conformational changes in a series of residues involved in the formation of active pockets assist MitM in binding SAH and mitomycin A. In particular, the 28ALGAASLGE36 loop changes most significantly. When mitomycin A binds, the bending direction of this loop is reversed, changing the entrance of the active site from open to closed. This study provides structural insights into MitM\'s involvement in the postmitosane stage of mitomycin biosynthesis and provides a template for the engineering of methyltransferases.
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  • 文章类型: Case Reports
    一名患者在用丝裂霉素C和干扰素治疗可疑的眼鳞状表面瘤形成五个月后出现角膜巩膜变薄。出于构造和美学目的,我们决定进行板层角膜巩膜移植。使用的方法建立了新的构造支持和角膜稳态。这种技术在类似情况下可能是一种选择。
    A patient presented with corneoscleral thinning five months after the treatment of suspected ocular squamous surface neoplasia with mitomycin-C and interferon. For tectonic and aesthetic purposes, we decided to perform lamellar corneoscleral transplantation. The approach used established new tectonic support and corneal homeostasis. This technique might be an option in similar cases.
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  • 文章类型: Journal Article
    在暴露于500ng/ml烷基化诱变剂丝裂霉素C(MMC)和5μM阿托伐他汀的人冠状动脉(HCAEC)和胸廓内动脉(HITAEC)内皮细胞中测量细胞因子表达水平。发现用阿托伐他汀治疗MMC暴露的HCAEC可减少巨噬细胞移动抑制因子(MIF)的分泌,IL-8和IL8基因表达,但增加了编码PAI-1蛋白的SERPINE1基因的表达。在阿托伐他汀治疗的HITAEC中,MIF蛋白浓度降低,IL8和SERPINE1基因表达降低。我们可以得出结论,阿托伐他汀可以防止在基因毒性负荷条件下培养的内皮细胞的促炎激活。然而,这种效应的分子机制需要进一步研究。
    The level of cytokine expression was measured in human coronary artery (HCAEC) and internal thoracic artery (HITAEC) endothelial cells exposed to 500 ng/ml alkylating mutagen mitomycin C (MMC) and 5 μM atorvastatin. It was found that treatment of MMC-exposed HCAEC with atorvastatin decreased secretion of macrophage migration inhibitory factor (MIF), IL-8, and IL8 gene expression, but increased the expression of SERPINE1 gene encoding the PAI-1 protein. In atorvastatin-treated HITAEC, the concentration of MIF protein and the expression of the IL8 and SERPINE1 genes were reduced. We can conclude that atorvastatin prevents proinflammatory activation of endothelial cells cultured under conditions of genotoxic load. However, the molecular mechanisms of this effect require further research.
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  • 文章类型: Journal Article
    伴有腹膜转移的结直肠癌(CRC)是一种复杂的疾病,其治疗提出了重大的临床挑战。在经验丰富的中心精心挑选的患者中,CRS/高温腹膜内化疗(HIPEC)可以以可接受的发病率进行,并与延长的生存期相关。根据近期随机对照试验的结果,不再建议在CRS后使用奥沙利铂的HIPEC,灌注期缩短(30分钟)。有一种趋势是利用丝裂霉素C作为延长灌注时间(90-120分钟)的一线腹膜内药物;然而,目前几乎没有潜在证据支持其广泛使用。
    Colorectal cancer (CRC) with peritoneal metastases is a complex disease and its management presents significant clinical challenges. In well-selected patients at experienced centers, CRS/hyperthermic intraperitoneal chemotherapy (HIPEC) can be performed with acceptable morbidity and is associated with prolonged survival. Based on the results of recent randomized controlled trials, HIPEC using oxaliplatin after CRS with shortened perfusion periods (30 minutes) is no longer recommended. There is a movement toward utilizing mitomycin C as a first-line intraperitoneal agent with extended perfusion times (90-120 minutes); however, there is currently little prospective evidence to support its widespread use.
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  • 文章类型: Journal Article
    背景:中危(IR)非肌肉浸润性膀胱癌(NMIBC)与高肿瘤复发率相关。为了改善患者的预后,建议使用辅助膀胱内治疗,丝裂霉素C(MMC)或卡介苗(BCG)。吉西他滨(GMC)是用于尿路上皮癌的已知分子。我们旨在研究吉西他滨溶液的疗效和安全性,与丝裂霉素C相比,在IRNMIBC的治疗中。
    方法:在这项回顾性研究中,我们从两个参与中心选择了2016-2020年间治疗的IRNMIBC患者,这些患者使用吉西他滨(中心A)作为膀胱内化疗方案或丝裂霉素C(中心B).主要终点是复发率,次要终点是治疗中断及其原因。
    结果:在我们102名IRNMIBC患者的队列中,49例患者接受了GMC和53MMC,中位随访时间为30个月。总复发率为42.1%,GMC组为22.4%,MMC组为60.3%(p<0.01)。在多因素分析中也发现了这种差异。所有患者中有14.7%出现病程中断,主要归因于不良事件(46.6%),组间无差异。
    结论:与MMC相比,在IRNMIBC患者中,辅助吉西他滨膀胱内治疗似乎是一种有趣的选择,与较低的肿瘤复发率和良好的耐受性有关。需要更大规模的前瞻性随机试验来验证我们的发现。
    BACKGROUND: Intermediate-risk (IR) Non-Muscle Invasive Bladder Cancer (NMIBC) is associated with a high rate of tumor recurrence. To improve patient outcomes, it is recommended to use adjuvant intravesical therapy, by mitomycin C (MMC) or Bacillus Calmette Guerin (BCG). Gemcitabine (GMC) is a known molecule used in urothelial cancer. We aimed to study the efficacy and safety profile of a gemcitabine solution, compared to mitomycin C, in the treatment of IR NMIBC.
    METHODS: In this retrospective study, patients with IR NMIBC treated between 2016 and 2020 were selected from two participating centers using either gemcitabine (center A) as the intravesical chemotherapy regimen or mitomycin C (center B). The primary endpoint was recurrence rate and secondary end points were treatment interruption and its causes.
    RESULTS: In our cohort of 102 IR NMIBC patients, 49 patients received GMC and 53 MMC with a median follow-up of 30 months. Overall recurrence rate was 42.1% with 22.4% in the GMC group and 60.3% in the MMC group (P<0.01). This difference was also found in the multifactorial analysis. Course interruption was observed in 14.7% of all patients, primarily attributed to adverse events (46.6%), without difference between groups.
    CONCLUSIONS: Adjuvant intravesical gemcitabine in patients with IR NMIBC seems to be an interesting option associated with a lower tumor recurrence rate and a favorable tolerance profile when compared to MMC. Larger scale prospective randomized trials are needed to validate our findings.
    METHODS: III.
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  • 文章类型: Journal Article
    背景:作为肺动脉高压(PH)的一种亚型,肺静脉闭塞性疾病(PVOD)是一种破坏性和危及生命的疾病,没有有效的治疗。据报道,在PH野百合碱诱导的大鼠模型中,氢具有抗氧化和抗炎作用。在这项研究中,我们研究了吸入氢气对丝裂霉素C(MMC)诱导的大鼠PVOD的预防和治疗作用。
    方法:雌性Sprague-Dawley大鼠腹腔注射3mg·kg-1·wk-1的MMC,连续2周诱导PVOD。同时或在MMC施用后两周通过设计的大鼠笼施用氢气(H2)的吸入。通过血液动力学测量和组织学分析评估PVOD的严重程度。一般对照非抑制型2(GCN2)的表达水平,核因子红系2相关因子2(Nrf2),测定肺组织中血红素加氧酶-1(HO-1)和内皮-间质转化(EndoMT)相关蛋白。测定血清中脂质过氧化促炎细胞因子的水平。
    结果:吸入H2改善了血流动力学和右心功能,右心室肥厚逆转,并在预防和治疗方法上防止肺血管重建。它降低了血清中丙二醛(MDA)水平和肺组织中NADPH氧化酶1(NOX-1)的表达。调节肺组织Nrf2/HO-1信号通路和抗炎因子GCN2,伴随着巨噬细胞和促炎细胞因子的减少。我们的数据表明,H2吸入有效对抗MMC诱导的EndoMT,通过检测内皮标志物(例如,VE-钙黏着蛋白和CD31)和间充质标志物(例如,波形蛋白和纤连蛋白)。进一步的研究表明,H2保留了p-Smad3并诱导了p-Smad1/5/9。
    结论:吸入H2可有效抑制MMC诱导的大鼠PVOD的发病机制。这种抑制作用可归因于H2的抗氧化和抗炎性质。
    BACKGROUND: As a subtype of pulmonary hypertension (PH), pulmonary veno-occlusive disease (PVOD) is devastating and life-threatening disease without effective therapy. Hydrogen has been reported to exhibits antioxidant and anti-inflammatory effects in a rat model induced by monocrotaline of PH. In this study, we investigated the effects of inhaled hydrogen gas on the prevention and treatment of PVOD induced by mitomycin C (MMC) in rats.
    METHODS: PVOD was induced in female Sprague-Dawley rats through intraperitoneal injection of MMC at a concentration of 3 mg·kg- 1·wk- 1 for 2 weeks. Inhalation of hydrogen gas (H2) was administered through a designed rat cage concurrently or two weeks after MMC administration. The severity of PVOD was assessed by using hemodynamic measurements and histological analysis. The expression levels of general control nonderepressible 2 (GCN2), nuclear factor erythroid 2-related factor-2 (Nrf2), heme oxygenase-1 (HO-1) and endothelial-to-mesenchymal transition (EndoMT) related proteins in lung tissue were measured. Levels of lipid peroxidation pro-inflammatory cytokines in serum were determined.
    RESULTS: Inhaled H2 improved hemodynamics and right heart function, reversed right ventricular hypertrophy, and prevented pulmonary vessel reconstitution in both prevention and treatment approaches. It decreased malondialdehyde (MDA) levels in the serum and the expression of NADPH oxidase 1 (NOX-1) in lung tissue. It regulated Nrf2/HO-1 signaling pathway and anti-inflammatory factor GCN2 in lung tissue, accompanied by a decrease in macrophages and pro-inflammatory cytokines. Our data suggested that H2 inhalation effectively countered EndoMT induced by MMC, as evidenced by the detection of endothelial markers (e.g., VE-cadherin and CD31) and mesenchymal markers (e.g., vimentin and fibronectin). Further research revealed that H2 preserved p-Smad3 and induced p-Smad1/5/9.
    CONCLUSIONS: Inhalation of H2 effectively inhibits the pathogenesis of PVOD induced by MMC in rats. This inhibitory effect may be attributed to the antioxidant and anti-inflammatory properties of H2.
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  • 文章类型: Journal Article
    耻垢分枝杆菌Nei2是一种单体酶,对单链DNA具有APβ-裂解酶活性。Nei2及其操纵子邻居Lhr(四聚体3'至5'解旋酶)的表达,在暴露于DNA损伤剂的分枝杆菌中诱导。这里,我们发现,nei2缺失使耻垢分枝杆菌对DNA链间交联剂三甲基补骨脂素的杀伤敏感,但对交联剂丝裂霉素C和顺铂的杀伤不敏感。相比之下,lhr的缺失对所有三种交联剂的杀伤敏感。我们报告了重组Nei2的1.45µ晶体结构,该结构由位于适合DNA结合的中央凹槽两侧的N和C末端叶组成。C叶包括四半胱氨酸锌络合物。突变分析鉴定了N末端脯氨酸残基(ORF的Pro2)和Lys51,但不是Glu3,是AP裂解酶活性所必需的。我们发现Nei2在单链DNA上具有5-羟基尿嘧啶糖基化酶活性,该活性被Glu3和Lys51的丙氨酸突变而不是Pro2的丙氨酸突变所消除。通过κnei2细胞中野生型和突变型nei2等位基因的表达来测试补骨脂素敏感性,确定AP裂解酶活性对于交联修复既不足够也不重要。相比之下,突变型lhr等位基因对Δlhr细胞补骨脂素敏感性的补充取决于Lhr的ATP酶/解旋酶活性及其四聚体四级结构。lhr-nei2操纵子包含独特的细菌系统以纠正链间交联。重要DNA链间交联剂丝裂霉素C,顺铂,补骨脂素-UVA在临床上用于治疗癌症和皮肤病;它们在阐明真核系统中链间交联修复的途径方面具有非常重要的价值。尽管已知DNA交联剂会引发细菌中的DNA损伤反应,细菌交联修复因子的花名册是不完整的,并且可能在分类单元之间有所不同。这项研究暗示DNA损伤可诱导的分枝杆菌lhr-nei2基因操纵子可以保护耻垢分枝杆菌免受链间交联剂的杀死。尽管阻断Lhr解旋酶的活性会使分枝杆菌对丝裂霉素C敏感,顺铂,和补骨脂素-UVA,Nei2糖基化酶在避免补骨脂素-UVA引起的损伤中起独特的作用。
    Mycobacterium smegmatis Nei2 is a monomeric enzyme with AP β-lyase activity on single-stranded DNA. Expression of Nei2, and its operonic neighbor Lhr (a tetrameric 3\'-to-5\' helicase), is induced in mycobacteria exposed to DNA damaging agents. Here, we find that nei2 deletion sensitizes M. smegmatis to killing by DNA inter-strand crosslinker trimethylpsoralen but not to crosslinkers mitomycin C and cisplatin. By contrast, deletion of lhr sensitizes to killing by all three crosslinking agents. We report a 1.45 Å crystal structure of recombinant Nei2, which is composed of N and C terminal lobes flanking a central groove suitable for DNA binding. The C lobe includes a tetracysteine zinc complex. Mutational analysis identifies the N-terminal proline residue (Pro2 of the ORF) and Lys51, but not Glu3, as essential for AP lyase activity. We find that Nei2 has 5-hydroxyuracil glycosylase activity on single-stranded DNA that is effaced by alanine mutations of Glu3 and Lys51 but not Pro2. Testing complementation of psoralen sensitivity by expression of wild-type and mutant nei2 alleles in ∆nei2 cells established that AP lyase activity is neither sufficient nor essential for crosslink repair. By contrast, complementation of psoralen sensitivity of ∆lhr cells by mutant lhr alleles depended on Lhr\'s ATPase/helicase activities and its tetrameric quaternary structure. The lhr-nei2 operon comprises a unique bacterial system to rectify inter-strand crosslinks.IMPORTANCEThe DNA inter-strand crosslinking agents mitomycin C, cisplatin, and psoralen-UVA are used clinically for the treatment of cancers and skin diseases; they have been invaluable in elucidating the pathways of inter-strand crosslink repair in eukaryal systems. Whereas DNA crosslinkers are known to trigger a DNA damage response in bacteria, the roster of bacterial crosslink repair factors is incomplete and likely to vary among taxa. This study implicates the DNA damage-inducible mycobacterial lhr-nei2 gene operon in protecting Mycobacterium smegmatis from killing by inter-strand crosslinkers. Whereas interdicting the activity of the Lhr helicase sensitizes mycobacteria to mitomycin C, cisplatin, and psoralen-UVA, the Nei2 glycosylase functions uniquely in evasion of damage caused by psoralen-UVA.
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