Overcoming resistance to rapalogs in gliomas by combinatory therapies

Glioblastoma is the most common and aggressive brain tumor type, with a mean patient survival of approximately 1 year. Many previous analyses of the glioma kinome have identified key deregulated pathways that converge and activate mammalian target of rapamycin (mTOR). Following the identification and characterization of mTOR-promoting activity in gliomagenesis, data from preclinical studies suggested the targeting of mTOR by rapamycin or its analogs (rapalogs) as a promising therapeutic approach. However, clinical trials with rapalogs have shown very limited efficacy on glioma due to the development of resistance mechanisms. Analysis of rapalog-insensitive glioma cells has revealed increased activity of growth and survival pathways compensating for mTOR inhibition by rapalogs that are suitable for therapeutic intervention. In addition, recently developed mTOR inhibitors show high anti-glioma activity. In this review, we recapitulate the regulation of mTOR signaling and its involvement in gliomagenesis, discuss mechanisms resulting in resistance to rapalogs, and speculate on strategies to overcome resistance. This article is part of a Special Issue entitled: Inhibitors of Protein Kinases (2012).     

暴发脑膜脑炎流行的新型毒株的全基因序列

吉林省延边地区１９９６年６月发生无菌性脑膜脑炎流行,从病人脑脊液和粪便标本中分离到多株病毒,血清学实验证明所分离的病毒为此次无菌性脑膜脑炎流行的病因。对其中的２株病毒（Ｙａｎｂｉａｎ９６－８３ｃｓｆ和Ｙａｎｂｉａｎ９６－８５ｃｓｆ）测定了全基因核酸序列并帮了比较分析。结果所测２株病毒核酸长度均为７４５６ｂｐ〔包括３端ｐｏｌｙ（Ａ）尾〕,两者间仅有１３个位点不同,同源性达９９．８％,在进化树上位于同     

Designing repeat proteins: modular leucine-rich repeat protein libraries based on the mammalian ribonuclease inhibitor family

We present a novel approach to design repeat proteins of the leucine-rich repeat (LRR) family for the generation of libraries of intracellular binding molecules. From an analysis of naturally occurring LRR proteins, we derived the concept to assemble repeat proteins with randomized surface positions from libraries of consensus repeat modules. As a guiding principle, we used the mammalian ribonuclease inhibitor (RI) family, which comprises cytosolic LRR proteins known for their extraordinary affinities to many RNases. By aligning the amino acid sequences of the internal repeats of human, pig, rat, and mouse RI, we derived a first consensus sequence for the characteristic alternating 28 and 29 amino acid residue A-type and B-type repeats. Structural considerations were used to replace all conserved cysteine residues, to define less conserved positions, and to decide where to introduce randomized amino acid residues. The so devised consensus RI repeat library was generated at the DNA level and assembled by stepwise ligation to give libraries of 2-12 repeats. Terminal capping repeats, known to shield the continuous hydrophobic core of the LRR domain from the surrounding solvent, were adapted from human RI. In this way, designed LRR protein libraries of 4-14 LRRs (equivalent to 130-415 amino acid residues) were obtained. The biophysical analysis of randomly chosen library members showed high levels of soluble expression in the Escherichia coli cytosol, monomeric behavior as characterized by gel-filtration, and alpha-helical CD spectra, confirming the success of our design approach.     

Characterization of VAMP-2 gene from marine teleostean, Lateolabrax japonicus

The whole length SPV2 gene of 715 bp, encoding VAMP-2 protein of 110 amino acids from Japanese sea perch, Lateolabrax japonicus, was obtained by using both RT-PCR and anchored PCR strategies while we initiated the structural and functional study on SNARE proteins in marine teleostean. Analysis of the deduced amino acid sequence indicated that SPV2 has its core arginine residue, a potential N-linked glycosylation site near its N-terminal, and one transmembrane domain in its C-terminal. Advanced structural analysis of bioinformatics approach predicts a coiled-coil α-helix backbone as the characteristic of SPV2 main conformational structure, identical to the structure of rat VAMP-2 obtained by crystallography. Semi-quantitative RT-PCR revealed that SPV2 was generally expressed in 10 neural and non-neural tissues, with the highest concentration in brain and the least in muscle.     

A rapid PCR-based method for genetically mapping ESTs

A simple, semi-automatable procedure was developed for converting expressed sequence tags (ESTs) into mappable genetic markers. The polymerase chain reaction is used to amplify regions immediately 5′ or 3′ to the coding regions of genes in order to maximise sequence variability between alleles. Fragment length and nucleotide substitution polymorphisms among amplified alleles can be detected using either ethidium bromide staining or automated laser-based fluorescence. A 6% non-denaturing acrylamide gel, analysed with an ABI 377 DNA sequencer, proved capable of resolving homoduplexes and heteroduplexes formed between amplified alleles containing nucleotide substitutions as well as resolving allelic length differences. With this approach 75% of 60 ESTs from a range of Pinus species could be genetically mapped in each of three pedigrees from P. radiata and P. taeda. Furthermore, three or four alleles were detected in each pedigree for 42% of the EST markers. Received: 4 January 2000 / Accepted: 26 May 2000     

Discovery of genes for ginsenoside biosynthesis by analysis of ginseng expressed sequence tags

Expressed sequence tags (ESTs) provide a valuable tool that can be used to identify genes in secondary metabolite biosynthesis. Ginseng (Panax ginseng C.A Meyer) is a medicinal plant that accumulates ginsenosides in roots. We sequenced 11,636 ESTs from five ginseng libraries in order to create a gene resource for biosynthesis of ginsenosides, which are thought to be the major active component in roots. Only 59% of the ginseng ESTs exhibited significant homology to previously known polypeptide sequences. Stress- and pathogen-response proteins were most abundant in 4-year-old ginseng roots. ESTs involved in ginsenoside biosynthesis were identified by a keyword search of BLASTX results and a domain search of ginseng ESTs. We identified 4 oxidosqualene cyclase candidates involved in the cyclization reaction of 2,3-oxidosqualene, 9 nine cytochrome P450 and 12 glycosyltransferse candidates, which may be involved in modification of the triterpene backbone.Abbreviations cDNA Complementary DNA - ESTs Expressed sequence tagsCommunicated by I.S. Chung     

Phylogeny of Allium L. subg. Melanocrommyum (Webb et Berth.) Rouy based on DNA sequence analysis of the internal transcribed spacer region of nrDNA

 Sequence analysis of the ITS region of nuclear ribosomal DNA from subgeneric representatives of Allium L. produced phylogenetic trees which concurred with previous conclusions based on classical taxonomy. Phylogenetic analysis revealed a closer relationship between Nectaroscordum siculum and Allium cernuum (representing Amerallium) than between A. cernuum and the rest of the Allium species employed in this study. The phylogeny of subg. Melanocrommyum based on ITS sequences largely agreed with inferences made by previous researchers based on morphology or a restriction analysis of chloroplast DNA. However, the phylogenetic positions of Allium protensum and Allium macleanii based on ITS sequences did not correspond to their morphological similarity with Allium schubertii and Allium giganteum, respectively. Received: 15 February 1998 / Accepted: 12 March 1998     

Archiascomycetes: detection of a major new lineage within the Ascomycota

For phylogenetic analysis of the higher fungi, we sequenced the nuclear small subunit rRNA (18S rRNA) gene fromTaphrina populina, the type species of the genusTaphrina, andProtomyces lactucae-debilis. The molecular phylogeny inferred from these 2 sequences and 75 sequences from the DNA data bank divided the Ascomycota into three major lineages: the hemiascomycetes, the euascomycetes, and the archiascomycetes, newly described herein. The former two lineages are monophyletic, whereas the archiascomycetes, which originated first and are comprised ofTaphrina, Protomyces, Saitoella, Schizosaccharomyces, andPneumocystis, may not be monophyletic. Among the archiascomycetes, theTaphrina/Protomyces branch is monophyletic. Confirmation of the archiascomycetes as a monophyletic taxonomic class will require comparison of additional genetically defined characters.This work was supported in part by grants 05454030 from the Ministry of Education, Science, and Culture of Japan (to J. S.) and 4369 from the Japan Society for the Promotion of Science Fellowship Programs (to H. N.).     

Survey of simple sequence repeats in completed fungal genomes

The use of simple sequence repeats or microsatellites as genetic markers has become very popular because of their abundance and length variation between different individuals. SSRs are tandem repeat units of 1 to 6 base pairs that are found abundantly in many prokaryotic and eukaryotic genomes. This is the first study examining and comparing SSRs in completely sequenced fungal genomes. We analyzed and compared the occurrences, relative abundance, relative density, most common, and longest SSRs in nine taxonomically different fungal species: Aspergillus nidulans, Cryptococcus neoformans, Encephalitozoon cuniculi, Fusarium graminearum, Magnaporthe grisea, Neurospora crassa, Saccharomyces cerevisiae, Schizosaccharomyces pombe, and Ustilago maydis. Our analysis revealed that, in all of the genomes studied, the occurrence, abundance, and relative density of SSRs varied and was not influenced by the genome sizes. No correlation between relative abundance and the genome sizes was observed, but it was shown that N. crassa, the largest genome analyzed had the highest relative abundance of SSRs. In most genomes, mononucleotide, dinucleotide, and trinucleotide repeats were more abundant than the longer repeated SSRs. Generally, in each organism, the occurrence, relative abundance, and relative density of SSRs decreased as the repeat unit increased. Furthermore, each organism had its own common and longest SSRs. Our analysis showed that the relative abundance of SSRs in fungi is low compared with the human genome and that longer SSRs in fungi are rare. In addition to providing new information concerning the abundance of SSRs for each of these fungi, the results provide a general source of molecular markers that could be useful for a variety of applications such as population genetics and strain identification of fungal organisms.