Potent in vitro Interference of Fleroxacin in DNA-binding, Unwinding and ATPase Activities of Bloom Helicase

Objective To study the effect of fleroxacin(FLRX) on biological properties of Bloom(BLM) helicase catalytic core(BLM 642-1290 helicase) in vitro and the molecular mechanism of interaction between the two molecules.Methods DNA-binding and unwinding activities of BLM 642-1290 helicase were assayed by fluorescence polarization and gel retardation assay under conditions that the helicase was subjected to different concentrations of FLRX.Effect of FLRX on helicase ATPase activity was analyzed by phosphorus-free assay based on a colorimetric estimation of ATP hydrolysis-produced inorganic phosphate.Molecular mechanism ofinteractionbetween thetwomoleculeswasassayedbyultraviolet andfluorescence spectra.Results The DNA unwinding and ATPase activities of BLM 642-1290 helicase were inhibited whereas the DNA-binding activity was promoted in vitro.A BLM-FLRX complex was formed through one binding site,electrostatic and hydrophobic interaction force.Moreover,the intrinsic fluorescence of the helicase was quenched by FLRX as a result of non-radioactive energy transfer.The biological activity of helicase was affected by FLRX,which may be through an allosteric mechanism and stabilization of enzyme conformation in low helicase activity state,disruption of the coupling of ATP hydrolysis to unwinding,and blocking helicase translocation on DNA strands.Conclusion FLRX may affect the biological activities and conformation of BLM 642-1290 helicase,and DNA helicase may be used as a promising drug target for some diseases.     

Similar roles for yeast Dbp2 and Arabidopsis RH20 DEAD-box RNA helicases to Ded1 helicase in tombusvirus plus-strand synthesis

Recruited host factors aid replication of plus-strand RNA viruses. In this paper, we show that Dbp2 DEAD-box helicase of yeast, which is a homolog of human p68 DEAD-box helicase, directly affects replication of Tomato bushy stunt virus (TBSV). We demonstrate that Dbp2 binds to the 3′-end of the viral minus-stranded RNA and enhances plus-strand synthesis by the viral replicase in a yeast-based cell-free TBSV replication assay. In vitro data with wt and an ATPase-deficient Dbp2 mutant indicate that Dbp2 unwinds local secondary structures at the 3′-end of the TBSV (−)RNA. We also show that Dbp2 complements the replication deficiency of TBSV in yeast containing reduced amount of Ded1 DEAD-box helicase, another host factor involved in TBSV replication, suggesting that Dbp2 and Ded1 helicases play redundant roles in TBSV replication. We also show that the orthologous AtRH20 DEAD-box helicase from Arabidopsis can increase tombusvirus replication in vitro and in yeast.     

Multiplicity of DNA end resection machineries in chromosome break repair

DNA end resection is critical for chromosome break repair by homologous recombination and influences the efficiency of repair by nonhomologous DNA end joining. An elegant study by Sinha and colleagues (pp. 1423–1437) published in the June 15, 2009, issue of Genes & Development identified a novel mycobacterial DNA end resection protein complex, AdnAB, that harbors dual DNA motor and dual nuclease functions. Sinha and colleagues also demonstrated that the DNA end-binding protein complex Ku regulates the activity of AdnAB.     

沉默CHD1L对前列腺癌PC3细胞恶性生物学行为的影响及其可能机制

目的:探讨染色质解旋酶DNA结合蛋白1样基因(chromodomain helicase/ATPase DNA binding protein 1-like gene,CHD1L)对前列腺癌细胞侵袭、迁移能力的影响及其可能的作用机制.方法:采用实时荧光定量PCR技术检测前列腺癌细胞株LNCAP、PC3、DU145以及前列腺上皮细胞株RWPE-1中CHD1L mRNA表达水平;转染siRNA干扰前列腺癌PC3细胞CHD1L的表达,并用Transwell侵袭实验和划痕实验分析沉默CHD1L对前列腺癌细胞侵袭和迁移能力的影响;Western blotting 检测PC3细胞MMP-9、N-钙黏蛋白和E-钙黏蛋白的表达水平.结果:CHD1L mRNA在前列腺癌细胞中的表达水平明显高于前列腺上皮细胞(P＜0.01),其中以前列腺癌PC3细胞的表达水平最高.侵袭实验中,干扰组的穿膜细胞数明显低于阴性对照组和空白对照组[(49.67 ±6.67)vs(113.67 ±5.69)和(112.00±12.49)个,P＜0.05).划痕实验中,干扰组48 h伤口愈合率也低于阴性对照组和空白对照组[(21.27 ±3.27)％ vs(48.47±5.72)％和(49.93±3.35)％,P＜0.05].干扰组细胞MMP-9和N-钙黏蛋白表达下调,E-钙黏蛋白表达上调.结论:沉默CHD1L可降低前列腺癌PC3细胞的侵袭迁移能力,该作用可能是通过调控MMP-9和EMT相关蛋白表达实现的.     

Peripheral nerve pathology at fixed stage in spinal muscular atrophy with respiratory distress type 1

Spinal muscular atrophy with respiratory distress type 1 (SMARD1) is characterized by severe respiratory failure due to diaphragmatic paralysis and distal muscular weakness in early infancy. After an initial decline in respiratory state and motor function until 1–2 years of age, residual capabilities reach a plateau.We report the peripheral neuropathological findings of a patient with SMARD1 at 1 year and 1 month of age, when his muscle strength and respiratory symptoms had deteriorated and then stabilized for several months. Peripheral nerve biopsy revealed severely progressed axonal degeneration. This finding suggests the rapid progression of peripheral axonal neuropathy in SMARD1 that leads to its characteristic clinical course of respiratory failure and paralysis in the early infantile period.     

Small fibre neuropathy in mitochondrial diseases explored with sudoscan

Objective

Polyneuropathy in mitochondrial diseases (MDs) is relatively common and widely investigated, but few data are instead reported about small fibres involvement.

The Tolypocladium inflatum CPA element encodes a RecQ helicase-like gene

Previously, a repetitive CPA element was discovered in the genome of the filamentous fungus Tolypocladium inflatum; however, no further characterization was technically possible at that time. In this study, PCR amplification was used to detect a 4 kb conserved portion of the CPA element that appeared to be present in most, if not all, genomic CPA elements. The amplicons included a large open reading frame that was most similar to a RecQ helicase-like gene from Metarhizium anisopliae. The repetitive nature of the CPA element suggests that it is related to the eukaryotic Helitron class of transposable elements.     

Interferon antagonist function of Japanese encephalitis virus NS4A and its interaction with DEAD-box RNA helicase DDX42

The interferon (IFN) antagonists of Japanese encephalitis virus (JEV) proteins contribute to the JE pathogenesis. Most flavivirus non-structural (NS) proteins correlate with virus-induced inflammation and immune escape. NS4A proteins of West Nile virus and dengue type 2 virus have been demonstrated to inhibit IFN signaling. In this study, JEV NS4A without the C-terminal 2K domain has been demonstrated to partially block activation of an IFN-stimulated response element (ISRE)-based cis-reporter by IFN-α/β. In addition, JEV NS4A significantly inhibited the phosphorylation levels of STAT1 and STAT2, but not TYK2 in the IFN-treated cells. Moreover, the N-terminus of a RNA helicase DDX42 protein identified using a phage display human brain cDNA library have been demonstrated to specifically bind to JEV NS4A in vitro using a co-immunoprecipitation assay. The interaction between JEV NS4A and RNA helicase DDX42 showed partial co-localization in human medulloblastoma TE-671 cells by confocal microscopy. Importantly, the expression of N-terminal DDX42 is able to overcome JEV-induced antagonism of IFN responses. Therefore, these results show that JEV NS4A without the C-terminal 2K domain is associated with modulation of the IFN response and the interaction of JEV NS4A with RNA helicase DDX42 could be important for JE pathogenesis.     

Identification of putative functional motifs in viral proteins essential for human cytomegalovirus DNA replication

Six of the eleven genes essential for Human cytomegalovirus (HCMV) DNA synthesis have been analyzed for putative structural motifs that may have a significant functional role in DNA replication. The genes studied encode for the DNA polymerase accessory protein (UL44), single-stranded DNA binding protein (UL57), primase-helicase complex (UL70, UL102, and UL105), and the putative initiator protein (UL84). The full-length open reading frames of these genes were highly conserved between ten isolates with amino acid sequence identity of >97% for all genes. Using ScanProsite software from the Expert Protein Analysis System (ExPASy) proteomics server, we have mapped putative motifs throughout these HCMV replication genes. Interesting motifs identified include casein kinase-2 (CKII) phosphorylation sites, a microbodies signal motif in UL57, and an ATP binding site in the putative UL105 helicase. Our investigations have also elucidated motif-rich regions of the UL44 DNA polymerase accessory protein and identified cysteine motifs that have potential implications for UL57 and UL70 primase. Taken together, these findings provide insights to regions of these HCMV replication proteins that are important for post-translation modification, activation, and overall function, and this information can be utilized to target further research into these proteins and advance the development of novel antiviral agents that target these processes.