Trypanosomal histone γH2A and the DNA damage response

DNA damage and repair in trypanosomatids impacts virulence, drug resistance and antigenic variation but, currently, little is known about DNA damage responses or cell cycle checkpoints in these divergent protozoa. One of the earliest markers of DNA damage in eukaryotes is γH2A(X), a serine phosphorylated histone H2A (variant). Here, we report the identification and initial characterization of γH2A in Trypanosoma brucei. We identified Thr(130) within the replication-dependent histone H2A as a candidate phosphorylation site and found that the abundance of this trypanosomal γH2A increased in vivo in response to DNA damage. Nuclear γH2A foci mark the sites of putative natural replication fork stalling, sites of meganuclease-induced DNA double strand breaks and sites of methyl methanesulphonate-induced DNA damage. Naturally occurring and meganuclease-induced γH2A and RAD51 double-positive repair foci are typically found in S-phase or G(2) nuclei. The results link trypanosomal γH2A, with an unusual histone modification motif, to DNA damage sensing and mitotic checkpoint signaling.     

1例滤泡型淋巴瘤患者BCL2区域多重DNA重排

滤泡型非何杰金氏淋巴瘤t(14:18)易位常见,其18号染色体的BCLZ基因易位到14号染色体免疫球蛋白重链座位的J区,在少数具t(14;18)易位的病例18号染色体BCL2基因3至少20kb处已识别出另一断裂点。本文描述1例滤泡型淋巴瘤患者BCL2基因的重排及后来的演变情况。男性患者,年龄39岁,1984年5月就诊时颈、锁骨上双侧淋巴结和腋淋巴结肿大,经颈淋巴结切除分析表明为B-K型CB/CC淋巴瘤,S期细胞呈低百分率(1.6%)。1985年3月该患者出现疲劳和盗汗症状,若干颈淋巴结肿大,取其中之一经检测表明为     

XRCC1与DNA修复

XRCC1是影响细胞对电离辐射的敏感性的第一个哺乳类动物基因。XRCC1通过与PARP、DNA连接酶Ⅲ和DNA多聚酶β等作用,在DNA损伤时单链断裂修复中起重要作用。现就XRCC1的分子生物学特性及XRCC1在DNA修复可能机制进行综述。     

XRCC1与DNA修复

XRCC1是影响细胞对电离辐射的敏感性的第一个哺乳类动物基因。XRCC1通过PARP、DNA连接酶Ⅲ和DNA多聚酶β等作用，在DNA损伤时单链断裂修复中起重要作用。现就XRCC1的分子生物学特性及XRCC1在DNA修复可能机制进行综述。     

Serum α1-antitrypsin and α2-macroglobulin in Alzheimer's and Binswanger's disease

The deposition of _A4-amyloid in senile plaques and small cerebral vessels is one of the pathological hallmarks of Alzheimer's disease. Recent data suggest that protease inhibitors such as ₂-macroglobulin may be involved in the process of forming _A4 amyloid deposits. Compared to 34 persons without neurological diseases, the serum content of al-antitrypsin was increased in 16 patients with Alzheimer's disease and 15 with Binswanger's disease. In the latter a2 macroglobulin was also elevated in serum. Our results show no evidence of a blood-borne origin of the protein or peptid deposited in the walls of small vessels in Alzheimer's or Binswanger's disease. Nevertheless, the elevated proteinase inhibitor concentrations may play a role in the pathogenesis of these diseases.Abbreviations AD Alzheimer's disease - APP -amyloid peptide precursor peptide - BD Binswanger's disease - IMCT Information-Memory-Concentration Test - MID multi-infarct dementia - MMSE Mini-Mental State Examination Correspondence to: T. Wetterling     

Axenfeld�CRieger syndrome and spectrum of PITX2 and FOXC1 mutations

Axenfeld–Rieger syndrome (ARS) is a rare autosomal dominant disorder, which encompasses a range of congential malformations affecting the anterior segment of the eye. ARS shows genetic heterogeneity and mutations of the two genes, PITX2 and FOXC1, are known to be associated with the pathogenesis. There are several excellent reviews dealing with the complexity of the phenotype and genotype of ARS. In this study, we will attempt to give a brief review of the clinical features and the relevant diagnostic approaches, together with a detailed review of published PITX2 and FOXC1 mutations.     

Study of DNA damage induction and repair capacity of fresh and cryopreserved lymphocytes exposed to H2O2 and γ-irradiation with the alkaline comet assay

The alkaline SCGE assay was evaluated for use with cryopreserved lymphocytes in order to obtain results similar to the freshly isolated ones. The induction of DNA damage as well as the repair capacity of γ-rays and H₂O₂ exposed cryopreserved human lymphocytes was found to be the same to that of the freshly isolated. Human lymphocytes (fresh or cryopreserved) responded differently to the effects of γ-irradiation if compared to the H₂O₂ treatment. The distribution of DNA damage among γ-irradiated lymphocytes was more homogeneous compared to H₂O₂, both in freshly isolated and in cryopreserved cells. 2.4 μg/ml phytohemagglutinin at the start of a 2-h incubation in RPMI of cryopreserved samples gave similar DNA repair and distribution patterns to the 2-h post-exposure incubation of freshly isolated lymphocytes. H₂O₂-induced DNA damage was not repaired completely. However, the repair of γ-rays-induced DNA damage was more efficient. These findings confirm the different mode of action of the two agents on the induction of DNA damage, as well as, the different response of the lymphocytes' DNA repair system.     

Distribution pattern of matrix metalloproteinases 1, 2, 3, and 9, tissue inhibitors of matrix metalloproteinases 1 and 2, and α2-macroglobulin in cases of generalized AA- and AL amyloidosis

Matrix metalloproteinases (MMPs) degrade basement membranes and connective tissue and play an essential role in the homeostasis of the extracellular matrix which is disrupted by the deposition of amyloid. This immunohistochemical study investigated the distribution pattern of matrix metalloproteinases (MMP-1, -2, -3, and -9) and their inhibitors [alpha 2-macroglobulin (alpha 2-M), tissue inhibitors of MMPs (TIMP)-1, and TIMP-2] in human AA- and AL amyloid deposits. Specimens of liver, kidney, and spleen from 22 autopsy cases were investigated. Nine patients had suffered from generalized AA amyloidosis, eight from generalized AL amyloidosis, and five from rheumatoid arthritis or tuberculosis with no histological evidence of amyloid. In all amyloidotic and non-amyloidotic patients, each protease and protease inhibitor was detected in almost every organ investigated. In the amyloidotic cases, there was no indication that a specific protease or protease inhibitor was absent or expressed, but a difference was observed in their spatial distribution patterns. The most noticeable difference was found in immunostaining of amyloid. Only MMP-1, -2, and -3, and alpha 2-M were present in AA amyloid deposits, and only TIMP-1 and TIMP-2 were found in deposits of AL amyloid. This is the first study to show that MMP-1, -2, and -3 are present in AA amyloid deposits. They may be involved in tissue remodeling or in proteolysis of the precursor and fibril proteins.     

The expression patterns and correlations of chibby, β-catenin, and DNA methyltransferase-1 and their clinicopathological significance in lung cancers

Xu H‐T, Li Q‐C, Dai S‐D, Xie X‐M, Liu D, Wang E‐H. The expression patterns and correlations of chibby, β‐catenin, and DNA methyltransferase‐1 and their clinicopathological significance in lung cancers. APMIS 2011; 119: 750–8. Chibby is an inhibitor of the Wnt pathway. The expression and correlation of chibby in lung cancers is unclear. We considered that the expression pattern of chibby might be related to the expression of β‐catenin and DNA methyltransferase‐1 (DNMT1). We examined the expressions of chibby, β‐catenin, and DNMT1 in 85 lung cancer tissues and corresponding normal lung tissues using immunohistochemistry. The nuclear expression rate of chibby was reduced in lung cancers (p < 0.001). Increased expression of DNMT1 was correlated with the differentiation (p = 0.034) and TNM stage (p = 0.048). The cytoplasmic expression of β‐catenin was correlated with poor differentiation of lung cancers (p = 0.016). The cytoplasmic and membrane expression of chibby was positively correlated with the cytoplasmic (p = 0.025) and membrane (p = 0.029) expressions of β‐catenin. The membrane expression of chibby was negatively correlated with the expression of DNMT1 (p = 0.006). Moreover, the expression of DNMT1 was correlated with the cytoplasmic expression of β‐catenin (p < 0.001). The nuclear expression of chibby is reduced in lung cancers. Chibby may colocalize with β‐catenin. β‐Catenin and DNMT1 may be concurrently expressed and thereby promote the development of lung cancers.     

Tel2: a common partner of PIK-related kinases and a link between DNA checkpoint and nutritional response?

A recent paper (Hayashi et al. 2007) in this issue of Genes to Cells shows that the fission yeast Schizosaccharomyces pombe Tel2, a homologue of mammalian/worm CLK2/Clk-2/Rad-5, physically interacts with all the phosphoinositide 3-kinase-related kinases (PIKKs) that include Rad3/Tel1 (ATR/ATM homologues), Tor1/Tor2 (TOR kinases) and Tra1/Tra2 (TRRAP homologues), raising the possibility that Tel2 family proteins link various PIKK-related cellular processes by interacting with PIKK family proteins. In this minireview, implications and impact of the findings, and a possibility that PIKKs are functionally related through Tel2, are discussed.     

IRAK-2 and PI 3-Kinase Synergistically Activate NF-κB and AP-1

Antisense interleukin-1 (IL-1) receptor associated kinase-2 (IRAK-2) oligonucleotide (ODN) and antisense p110 PI 3-kinase ODN blocked IRAK-2 and p110 PI 3-kinase expression, respectively. As a result, antisense IRAK-2 ODN or antisense p110 PI 3-kinase ODN inhibited IL-1-induced NF-B and AP-1 activation in HepG2 cells. The inhibition of NF-B activation by antisense IRAK-2 ODN or antisense p110 PI 3-kinase ODN and the inhibition of AP-1 activation by antisense IRAK-2 ODN were incomplete, whereas AP-1 activation could be inhibited by antisense p110 PI 3-kinase ODN completely. These results indicate that IRAK-2 is necessary but insufficient to activate NF-B and AP-1 completely and that although PI 3-kinase is not sufficient for NF-B full activation, it is sufficient to activate AP-1 completely. The effects of IRAK-2 or PI 3-kinase on NF-B and AP-1 activation were confirmed by the results that overexpression of IRAK-2 failed to fully activate NF-B and AP-1 and that overexpression of p110 PI 3-kinase is insufficient for NF-B full activation but sufficient for AP-1 activation. Cotransfection experiments showed that the combination of antisense IRAK-2 ODN and antisense p110 PI 3-kinase ODN resulted in additive inhibition of NF-B as well as AP-1 activation. On the other hand, coexpression of IRAK-2 with p110 PI 3-kinase led to a synergistic activation of NF-B and AP-1. These data suggest that IRAK-2 and PI 3-kinase cooperate to activate NF-B and AP-1.     

Th1 and Th2 subsets: paradigms lost?

The T helper 1 (Th1)/Th2 model has provided a valuable framework to investigate and explain many immune reactions and now pervades current thinking on the regulatory role of T cells. However, individual T cells and clones display remarkable diversity in their cytokine profiles, collectively forming a continuous spectrum in which Th1 and Th2 cells may be only two of the possible extreme phenotypes. For these reasons, Anne Kelso argues that cytokine-producing T cells cannot be classified into discrete subsets.     

Subgroups A1 and A2: Qualitative and/or Quantitative Distinctions?

In this editorial that was published in Immunological Communications, Special Issue on Immunohematology, volume 9, number 2, 1980, the authors unintentionally overlooked an important paper, which provides strong independent support for the interpretation of a structural, hence, qualitative, difference between subgroups A₁ and A₂. It is as follows:     

DNA修复基因XRCC 1研究进展

X线修复交叉互补基因1(XRCC 1)是一种重要的DNA修复基因,参与DNA单链断裂和碱基损伤修复,位于人染色体19q13.2,编码区单核苷酸多态位点导致相应的氨基酸改变.对其生物学特性、结构功能、基因多态与疾病易感性等方面的研究,可深入理解XRCC 1基因多态与环境交互作用对个体易感性的重要影响,其可能是某些疾病如癌症发生中潜在的易感标志物,对特定亚人群的筛检、预防和指导临床用药有深远意义.     

How does suppression of IGF-1 signaling by DNA damage affect aging and longevity?

Long-lived animals have evolved a robust set of defenses to maintain genomic integrity over their entire lifespan. The DNA damage response and DNA repair pathways are critical pillars of organismal defenses, minimizing somatic mutations in both post-mitotic and mitotic cells. These genomic maintenance systems not only prevent the premature emergence of cancers but may also maintain normal tissue function and organismal longevity. Genetic defects in a number of DNA repair and DNA damage response genes often leads to a dramatic increase in cancer incidence; in other cases, premature aging or progeroid syndromes may be induced. In this review, we discuss two recent reports of two nucleotide excision repair-deficient models that exhibit dramatic premature aging and shortened longevity. The DNA repair defects were also associated with a significant inhibition of the growth hormone/insulin-like growth factor 1 (GH/IGF-1) axis, an endocrine signaling pathway shown to influence aging and longevity in both vertebrates and invertebrates. Potential mechanisms of how DNA damage might affect IGF-1 signaling and aging are discussed, with a particular emphasis on the role of such signaling alterations in the adult tissue stem cell compartments.     

Anti-β2-glycoprotein I antibody with DNA binding activity enters living monocytes via cell surface DNA and induces tissue factor expression

Autoantibodies characteristic for anti-phospholipid syndrome (APS) and systemic lupus erythematosus (SLE) are anti-β₂-glycoprotein I (β₂GPI) antibodies and anti-DNA antibodies, respectively, and almost half of APS cases occur in SLE. Anti-β₂GPI antibodies are recognized to play a pivotal role in inducing a prothrombotic state, but the precise mechanism has not been fully elucidated. In a widely accepted view, binding of anti-β₂GPI antibodies to cell surface β₂GPI in monocytes and endothelial cells triggers the Toll-like receptor 4-myeloid differentiation primary response 88 (TLR)-4-MyD88) signaling pathway which leads to activation of p38 mitogen-activated protein kinase (MAPK), mitogen-activated protein kinase kinase 1/extracellular signal-regulated kinases (MEK-1/ERK) and/or nuclear factor kappa B (NF-κB) and expression of tissue factor (TF). However, resting cells do not express substantial amounts of TLR-4. Previously, we generated a mouse monoclonal anti-β₂GPI antibody WB-6 and showed that it induced a prothrombotic state – including TF expression on circulating monocytes – in normal mice. In the current study, we aimed to clarify the mechanism of interaction between WB-6 and resting monocytes, and found that WB-6 exhibits binding activity to DNA and enters living monocytes or a monocytic cell line and, to a lesser extent, vascular endothelial cells. Treatment of the cells with DNase I reduced the internalization, suggesting the involvement of cell surface DNA in this phenomenon. Monocytes harboring internalized WB-6 expressed TF and tumor necrosis factor (TNF)-α which, in turn, stimulated endothelial cells to express intercellular adhesion molecule 1 (ICAM-I) and vascular cell adhesion molecule 1 (VCAM-I). These results suggest the possibility that a subset of anti-β₂GPI antibodies with dual reactivity to DNA possesses ability to stimulate DNA sensors in the cytoplasm, in addition to the cell surface receptor-mediated pathways, leading to produce proinflammatory and prothrombotic states.     

登革病毒2型NS1蛋白DNA疫苗的构建及其免疫效果观察

目的　以登革病毒 2型 (denguevirus2 ,DV2 )非结构蛋白 (non structrulprotein 1,NS1)为靶基因 ,构建DV2 NS1的候选DNA疫苗 ;并探讨其在小鼠体内诱导特异性体液免疫和细胞免疫的作用。方法　将登革病毒 2型NS1 NS2a基因片段克隆至含AG强启动子的真核表达载体pCXN2上 ,构建成重组体pCXN2 NS1 NS2a。在体外将重组质粒转染Cos 7细胞 ,间接免疫荧光检测其在真核细胞中的表达。大量提取空质粒和重组质粒 ,进行动物免疫实验。结果　重组质粒可在真核细胞中有效地表达NS1蛋白。免疫接种小鼠后可诱发机体产生针对NS1蛋白的特异性体液免疫和细胞免疫。末次免疫前已有抗体产生 ,4周后达高峰。抗体依赖补体介导的溶细胞作用 (antibody dependentcomple ment mediatedcytolysis,ADCC)试验结果显示产生的抗体在体外具有特异的杀细胞作用。淋巴细胞增殖实验结果显示 ,实验组小鼠的淋巴细胞增殖能力与对照组比较差异有显著性。流式细胞计数仪(FACS)检测DNA免疫鼠CD4 + 、CD8+ T淋巴细胞变化情况 ,与注射空载体pCXN2的阴性鼠相比 ,CD4 + 、CD8+ 细胞水平有较大升高 (P <0 .0 1)。动物保护性实验结果显示 ,当用致死剂量登革病毒攻击免疫鼠时 ,有 6 6 .6 %的免疫鼠受到保护。结论　NS1 NS2a基因重组质粒免疫小鼠可以诱