Showing papers on "genomic DNA published in 2010"

Detection of inherited mutations for breast and ovarian cancer using genomic capture and massively parallel sequencing

Abstract: Inherited loss-of-function mutations in the tumor suppressor genes BRCA1, BRCA2, and multiple other genes predispose to high risks of breast and/or ovarian cancer. Cancer-associated inherited mutations in these genes are collectively quite common, but individually rare or even private. Genetic testing for BRCA1 and BRCA2 mutations has become an integral part of clinical practice, but testing is generally limited to these two genes and to women with severe family histories of breast or ovarian cancer. To determine whether massively parallel, “next-generation” sequencing would enable accurate, thorough, and cost-effective identification of inherited mutations for breast and ovarian cancer, we developed a genomic assay to capture, sequence, and detect all mutations in 21 genes, including BRCA1 and BRCA2, with inherited mutations that predispose to breast or ovarian cancer. Constitutional genomic DNA from subjects with known inherited mutations, ranging in size from 1 to >100,000 bp, was hybridized to custom oligonucleotides and then sequenced using a genome analyzer. Analysis was carried out blind to the mutation in each sample. Average coverage was >1200 reads per base pair. After filtering sequences for quality and number of reads, all single-nucleotide substitutions, small insertion and deletion mutations, and large genomic duplications and deletions were detected. There were zero false-positive calls of nonsense mutations, frameshift mutations, or genomic rearrangements for any gene in any of the test samples. This approach enables widespread genetic testing and personalized risk assessment for breast and ovarian cancer.

Sensitive enzymatic quantification of 5-hydroxymethylcytosine in genomic DNA

Abstract: The recent discovery of genomic 5-hydroxymethylcytosine (hmC) and mutations affecting the respective Tet hydroxylases in leukemia raises fundamental questions about this epigenetic modification. We present a sensitive method for fast quantification of genomic hmC based on specific transfer of radiolabeled glucose to hmC by a purified glucosyltransferase. We determined hmC levels in various adult tissues and differentiating embryonic stem cells and show a correlation with differential expression of tet genes.

Genome-wide characterization of simple sequence repeats in cucumber (Cucumis sativus L.)

Abstract: Cucumber, Cucumis sativus L. is an important vegetable crop worldwide. Until very recently, cucumber genetic and genomic resources, especially molecular markers, have been very limited, impeding progress of cucumber breeding efforts. Microsatellites are short tandemly repeated DNA sequences, which are frequently favored as genetic markers due to their high level of polymorphism and codominant inheritance. Data from previously characterized genomes has shown that these repeats vary in frequency, motif sequence, and genomic location across taxa. During the last year, the genomes of two cucumber genotypes were sequenced including the Chinese fresh market type inbred line '9930' and the North American pickling type inbred line 'Gy14'. These sequences provide a powerful tool for developing markers in a large scale. In this study, we surveyed and characterized the distribution and frequency of perfect microsatellites in 203 Mbp assembled Gy14 DNA sequences, representing 55% of its nuclear genome, and in cucumber EST sequences. Similar analyses were performed in genomic and EST data from seven other plant species, and the results were compared with those of cucumber. A total of 112,073 perfect repeats were detected in the Gy14 cucumber genome sequence, accounting for 0.9% of the assembled Gy14 genome, with an overall density of 551.9 SSRs/Mbp. While tetranucleotides were the most frequent microsatellites in genomic DNA sequence, dinucleotide repeats, which had more repeat units than any other SSR type, had the highest cumulative sequence length. Coding regions (ESTs) of the cucumber genome had fewer microsatellites compared to its genomic sequence, with trinucleotides predominating in EST sequences. AAG was the most frequent repeat in cucumber ESTs. Overall, AT-rich motifs prevailed in both genomic and EST data. Compared to the other species examined, cucumber genomic sequence had the highest density of SSRs (although comparable to the density of poplar, grapevine and rice), and was richest in AT dinucleotides. Using an electronic PCR strategy, we investigated the polymorphism between 9930 and Gy14 at 1,006 SSR loci, and found unexpectedly high degree of polymorphism (48.3%) between the two genotypes. The level of polymorphism seems to be positively associated with the number of repeat units in the microsatellite. The in silico PCR results were validated empirically in 660 of the 1,006 SSR loci. In addition, primer sequences for more than 83,000 newly-discovered cucumber microsatellites, and their exact positions in the Gy14 genome assembly were made publicly available. The cucumber genome is rich in microsatellites; AT and AAG are the most abundant repeat motifs in genomic and EST sequences of cucumber, respectively. Considering all the species investigated, some commonalities were noted, especially within the monocot and dicot groups, although the distribution of motifs and the frequency of certain repeats were characteristic of the species examined. The large number of SSR markers developed from this study should be a significant contribution to the cucurbit research community.

Targeted chromosomal deletions in human cells using zinc finger nucleases

Abstract: We present a novel approach for generating targeted deletions of genomic segments in human and other eukaryotic cells using engineered zinc finger nucleases (ZFNs). We found that ZFNs designed to target two different sites in a human chromosome could introduce two concurrent DNA double-strand breaks (DSBs) in the chromosome and give rise to targeted deletions of the genomic segment between the two sites. Using this method in human cells, we were able to delete predetermined genomic DNA segments in the range of several-hundred base pairs (bp) to 15 mega-bp at frequencies of 10−3 to 10−1. These high frequencies allowed us to isolate clonal populations of cells, in which the target chromosomal segments were deleted, by limiting dilution. Sequence analysis revealed that many of the deletion junctions contained small insertions or deletions and microhomologies, indicative of DNA repair via nonhomologous end-joining. Unlike other genome engineering tools such as recombinases and meganucleases, ZFNs do not require preinsertion of target sites into the genome and allow precise manipulation of endogenous genomic scripts in animal and plant cells. Thus, ZFN-induced genomic deletions should be broadly useful as a novel method in biomedical research, biotechnology, and gene therapy.

Role of Extracellular DNA during Biofilm Formation by Listeria monocytogenes

Abstract: Listeria monocytogenes is a food-borne pathogen that is capable of living in harsh environments. It is believed to do this by forming biofilms, which are surface-associated multicellular structures encased in a self-produced matrix. In this paper we show that in L. monocytogenes extracellular DNA (eDNA) may be the only central component of the biofilm matrix and that it is necessary for both initial attachment and early biofilm formation for 41 L. monocytogenes strains that were tested. DNase I treatment resulted in dispersal of biofilms, not only in microtiter tray assays but also in flow cell biofilm assays. However, it was also demonstrated that in a culture without eDNA, neither Listeria genomic DNA nor salmon sperm DNA by itself could restore the capacity to adhere. A search for additional necessary components revealed that peptidoglycan (PG), specifically N-acetylglucosamine (NAG), interacted with the DNA in a manner which restored adhesion. If a short DNA fragment (less than approximately 500 bp long) was added to an eDNA-free culture prior to addition of genomic or salmon sperm DNA, adhesion was prevented, indicating that high-molecular-weight DNA is required for adhesion and that the number of attachment sites on the cell surface can be saturated.

Array-based genomic resequencing of human leukemia

Abstract: To identify oncogenes in leukemias, we performed large-scale resequencing of the leukemia genome using DNA sequence arrays that determine approximately 9 Mbp of sequence corresponding to the exons or exon-intron boundaries of 5648 protein-coding genes. Hybridization of genomic DNA from CD34-positive blasts of acute myeloid leukemia (n=19) or myeloproliferative disorder (n=1) with the arrays identified 9148 nonsynonymous nucleotide changes. Subsequent analysis showed that most of these changes were also present in the genomic DNA of the paired controls, with 11 somatic changes identified only in the leukemic blasts. One of these latter changes results in a Met-to-Ile substitution at amino-acid position 511 of Janus kinase 3 (JAK3), and the JAK3(M511I) protein exhibited transforming potential both in vitro and in vivo. Further screening for JAK3 mutations showed novel and known transforming changes in a total of 9 out of 286 cases of leukemia. Our experiments also showed a somatic change responsible for an Arg-to-His substitution at amino-acid position 882 of DNA methyltransferase 3A, which resulted in a loss of DNA methylation activity of >50%. Our data have thus shown a unique profile of gene mutations in human leukemia.

Multiple displacement amplification compromises quantitative analysis of metagenomes

Abstract: significant (P ≤ 0.05), albeit unidirectional, skewing that would compromise quantitative comparisons (Supplementary Tables 2 and 4). This suggests that community composition itself is also a determinant of MDA-mediated representational bias. The observed bias in small-subunit rRNA-derived OTUs is highly likely to translate to bias in relative genome coverage of community members5. We therefore recommend that quantitative inferences6 should not be made from comparison of MDA-amplified environmental nucleic acids using the kits we tested until the source of the bias is understood and can be corrected, and that other MDA protocols should be rigorously validated before use in quantitative comparisons of environmental samples.

Small-molecule-mediated G-quadruplex isolation from human cells

Abstract: Nucleic acids containing stretches of tandem guanines can fold into four-stranded structures called G-quadruplexes. The existence of such sequences in genomic DNA suggests the occurrence of these motifs in cells, with potential implications in a number of biological processes relevant to cancer. Small molecules have proven to be valuable tools to dissect cell circuitry. Here, we describe a synthetic small molecule derived from an N,N'-bis(2-quinolinyl)pyridine-2,6-dicarboxamide, which is designed to mediate the selective isolation of G-quadruplex nucleic acids. The methodology was successfully applied to a range of DNA and RNA G-quadruplexes in vitro. We demonstrate the general applicability of the method by isolating telomeric DNA-containing G-quadruplex motifs from cells. We show that telomeres are targets for the probe, providing further evidence of the formation of G-quadruplexes in human cells.

Contamination of human DNA samples with mouse DNA can lead to false detection of XMRV-like sequences.

Abstract: In 2006, a novel gammaretrovirus, XMRV (xenotropic murine leukemia virus-related virus), was discovered in some prostate tumors. A more recent study indicated that this infectious retrovirus can be detected in 67% of patients suffering from chronic fatigue syndrome (CFS), but only very few healthy controls (4%). However, several groups have published to date that they could not identify XMRV RNA or DNA sequences in other cohorts of CFS patients, while another group detected murine leukemia virus (MLV)-like sequences in 87% of such patients, but only 7% of healthy controls. Since there is a high degree of similarity between XMRV and abundant endogenous MLV proviruses, it is important to distinguish contaminating mouse sequences from true infections. DNA from the peripheral blood of 112 CFS patients and 36 healthy controls was tested for XMRV with two different PCR assays. A TaqMan qPCR assay specific for XMRV pol sequences was able to detect viral DNA from 2 XMRV-infected cells (~ 10-12 pg DNA) in up to 5 μg of human genomic DNA, but yielded negative results in the test of 600 ng genomic DNA from 100,000 peripheral blood cells of all samples tested. However, positive results were obtained with some of these samples, using a less specific nested PCR assay for a different XMRV sequence. DNA sequencing of the PCR products revealed a wide variety of virus-related sequences, some identical to those found in prostate cancer and CFS patients, others more closely related to known endogenous MLVs. However, all samples that tested positive for XMRV and/or MLV DNA were also positive for the highly abundant intracisternal A-type particle (IAP) long terminal repeat and most were positive for murine mitochondrial cytochrome oxidase sequences. No contamination was observed in any of the negative control samples, containing those with no DNA template, which were included in each assay. Mouse cells contain upwards of 100 copies each of endogenous MLV DNA. Even much less than one cell's worth of DNA can yield a detectable product using highly sensitive PCR technology. It is, therefore, vital that contamination by mouse DNA be monitored with adequately sensitive assays in all samples tested.

The AlkB Domain of Mammalian ABH8 Catalyzes Hydroxylation of 5‐Methoxycarbonylmethyluridine at the Wobble Position of tRNA

Abstract: The ABH8 protein (also called ALKBH8) is a member of the AlkB (alkylated DNA repair protein) family of nonheme iron/ α-ketoglutarate (αKG)-dependent dioxygenases.[1] Other members of this protein family are known to catalyze oxidative demethylation to repair damaged DNA/RNA.[2] AlkB-like proteins exist in viruses, bacteria, and eukaryotic species.[3] Nine mammalian homologues of AlkB (ABH1-ABH8, and FTO, a protein associated with fat mass and obesity) have been identified through bioinformatics studies.[1b,4] Four of the homologues (ABH1, ABH2, ABH3, and FTO) show demethylation activity for N-methylated bases, in either DNA or RNA, through the hydroxylation of the N-methyl group and subsequent release of an aldehyde from the oxidized intermediate.[5] ABH2, which repairs m1A, m3C, and eA (1,N 6-ethenoadenine) in dsDNA, guards mammalian genomic DNA against methylation damage.[6] ABH3 appears to be involved in RNA repair.[7] FTO was first identified in a fused-toes malformation phenotype resulting from a mouse genome deletion,[8] and was later shown to significantly affect energy homeostasis and lead to obesity.[9] FTO has the highest activity in demethylating m3T in ssDNA and m3U in RNA;[4,10] however, the link between its biochemical activity and physiological phenotype is yet to be discovered. Aside from ABH1, ABH2, ABH3, and FTO, the biochemical activities of the other AlkB homologues are still unknown. Very recently Tet1, another iron(II)/αKG-dependent dioxygenase, has been shown to hydroxylate the 5-methyl group of m5C in dsDNA to form 5-hydroxymethylcytosine (hm5C) in certain neural and stem cells. This discovery has fueled speculation that this modification is important in epigenetics.[11]

Splinkerette PCR for Mapping Transposable Elements in Drosophila

Abstract: Transposable elements (such as the P-element and piggyBac) have been used to introduce thousands of transgenic constructs into the Drosophila genome. These transgenic constructs serve many roles, from assaying gene/cell function, to controlling chromosome arm rearrangement. Knowing the precise genomic insertion site for the transposable element is often desired. This enables identification of genomic enhancer regions trapped by an enhancer trap, identification of the gene mutated by a transposon insertion, or simplifying recombination experiments. The most commonly used transgene mapping method is inverse PCR (iPCR). Although usually effective, limitations with iPCR hinder its ability to isolate flanking genomic DNA in complex genomic loci, such as those that contain natural transposons. Here we report the adaptation of the splinkerette PCR (spPCR) method for the isolation of flanking genomic DNA of any P-element or piggyBac. We report a simple and detailed protocol for spPCR. We use spPCR to 1) map a GAL4 enhancer trap located inside a natural transposon, pinpointing a master regulatory region for olfactory neuron expression in the brain; and 2) map all commonly used centromeric FRT insertion sites. The ease, efficiency, and efficacy of spPCR could make it a favored choice for the mapping of transposable element in Drosophila.

A new protocol for extraction of C0t-1 DNA from rice

Abstract: C0t-1 DNA, enriched for repetitive DNA sequences, has been proved to be valuable in the studies of plant species differentiation and genome evolution. A new protocol to steadily obtain the aimed range of DNA fragments has been developed by shearing the genomic DNA with the digest system containing

Mercury-associated DNA hypomethylation in polar bear brains via the LUminometric Methylation Assay: a sensitive method to study epigenetics in wildlife

Abstract: In this paper we describe a novel approach that may shed light on the genomic DNA methylation of organisms with non-resolved genomes. The LUminometric Methylation Assay (LUMA) is permissive for genomic DNA methylation studies of any genome as it relies on the use of methyl-sensitive and -insensitive restriction enzymes followed by polymerase extension via Pyrosequencing technology. Here, LUMA was used to characterize genomic DNA methylation in the lower brain stem region from 47 polar bears subsistence hunted in central East Greenland between 1999 and 2001. In these samples, average genomic DNA methylation was 57.9% ± 6.69 (SD; range was 42.0 to 72.4%). When genomic DNA methylation was related to brain mercury (Hg) exposure levels, an inverse association was seen between these two variables for the entire study population (P for trend = 0.17). After dichotomizing animals by gender and controlling for age, a negative trend was seen amongst male animals (P for trend = 0.07) but no associations were found in female bears. Such sexually dimorphic responses have been found in other toxicological studies. Our results show that genomic DNA methylation can be quantitatively studied in a highly reproducible manner in tissue samples from a wild organism with a non-resolved genome. As such, LUMA holds great promise as a novel method to explore consequential questions across the ecological sciences that may require an epigenetic understanding.

Use of Splicing Reporter Minigene Assay to Evaluate the Effect on Splicing of Unclassified Genetic Variants

Abstract: The interpretation of the numerous sequence variants of unknown biological and clinical significance (UV for "unclassified variant") found in genetic screenings represents a major challenge in the molecular diagnosis of genetic disease, including cancer susceptibility. A fraction of UVs may be deleterious because they affect mRNA splicing. Here, we describe a functional splicing assay based on a minigene construct that assesses the impact of sequence variants on splicing. A genomic segment encompassing the variant sequence of interest along with flanking intronic sequences is PCR-amplified from patient genomic DNA and is cloned into a minigene vector. After transient transfection into cultured cells, the splicing patterns of the transcripts generated from the wild-type and from the variant constructs are compared by reverse transcription-PCR analysis and sequencing. This method represents a complementary approach to reverse transcription-PCR analyses of patient RNA, for the identification of pathogenic splicing mutations.

The C-terminal domain of the bacterial SSB protein acts as a DNA maintenance hub at active chromosome replication forks.

Abstract: We have investigated in vivo the role of the carboxy-terminal domain of the Bacillus subtilis Single-Stranded DNA Binding protein (SSBCter) as a recruitment platform at active chromosomal forks for many proteins of the genome maintenance machineries. We probed this SSBCter interactome using GFP fusions and by Tap-tag and biochemical analysis. It includes at least 12 proteins. The interactome was previously shown to include PriA, RecG, and RecQ and extended in this study by addition of DnaE, SbcC, RarA, RecJ, RecO, XseA, Ung, YpbB, and YrrC. Targeting of YpbB to active forks appears to depend on RecS, a RecQ paralogue, with which it forms a stable complex. Most of these SSB partners are conserved in bacteria, while others, such as the essential DNA polymerase DnaE, YrrC, and the YpbB/RecS complex, appear to be specific to B. subtilis. SSBCter deletion has a moderate impact on B. subtilis cell growth. However, it markedly affects the efficiency of repair of damaged genomic DNA and arrested replication forks. ssbΔCter mutant cells appear deficient in RecA loading on ssDNA, explaining their inefficiency in triggering the SOS response upon exposure to genotoxic agents. Together, our findings show that the bacterial SSBCter acts as a DNA maintenance hub at active chromosomal forks that secures their propagation along the genome.

Stress Sensors and Signal Transducers in Cyanobacteria

Abstract: In living cells, the perception of environmental stress and the subsequent transduction of stress signals are primary events in the acclimation to changes in the environment. Some molecular sensors and transducers of environmental stress cannot be identified by traditional and conventional methods. Based on genomic information, a systematic approach has been applied to the solution of this problem in cyanobacteria, involving mutagenesis of potential sensors and signal transducers in combination with DNA microarray analyses for the genome-wide expression of genes. Forty-five genes for the histidine kinases (Hiks), 12 genes for serine-threonine protein kinases (Spks), 42 genes for response regulators (Rres), seven genes for RNA polymerase sigma factors, and nearly 70 genes for transcription factors have been successfully inactivated by targeted mutagenesis in the unicellular cyanobacterium Synechocystis sp. PCC 6803. Screening of mutant libraries by genome-wide DNA microarray analysis under various stress and non-stress conditions has allowed identification of proteins that perceive and transduce signals of environmental stress. Here we summarize recent progress in the identification of sensory and regulatory systems, including Hiks, Rres, Spks, sigma factors, transcription factors, and the role of genomic DNA supercoiling in the regulation of the responses of cyanobacterial cells to various types of stress.

Methods and compositions for long fragment read sequencing

Abstract: The present invention is directed to methods and compositions for long fragment read sequencing. The present invention encompasses methods and compositions for preparing long fragments of genomic DNA, for processing genomic DNA for long fragment read sequencing methods, as well as software and algorithms for processing and analyzing sequence data.

Extrachromosomal circles of satellite repeats and 5S ribosomal DNA in human cells

Abstract: Extrachomosomal circular DNA (eccDNA) is ubiquitous in eukaryotic organisms and was detected in every organism tested, including in humans. A two-dimensional gel electrophoresis facilitates the detection of eccDNA in preparations of genomic DNA. Using this technique we have previously demonstrated that most of eccDNA consists of exact multiples of chromosomal tandemly repeated DNA, including both coding genes and satellite DNA. Here we report the occurrence of eccDNA in every tested human cell line. It has heterogeneous mass ranging from less than 2 kb to over 20 kb. We describe eccDNA homologous to human alpha satellite and the Sst I mega satellite. Moreover, we show, for the first time, circular multimers of the human 5S ribosomal DNA (rDNA), similar to previous findings in Drosophila and plants. We further demonstrate structures that correspond to intermediates of rolling circle replication, which emerge from the circular multimers of 5S rDNA and Sst I satellite. These findings, and previous reports, support the general notion that every chromosomal tandem repeat is prone to generate eccDNA in eukryoric organisms including humans. They suggest the possible involvement of eccDNA in the length variability observed in arrays of tandem repeats. The implications of eccDNA on genome biology may include mechanisms of centromere evolution, concerted evolution and homogenization of tandem repeats and genomic plasticity.

Scaffolding a Caenorhabditis nematode genome with RNA-seq.

Abstract: Efficient sequencing of animal and plant genomes by next-generation technology should allow many neglected organisms of biological and medical importance to be better understood. As a test case, we have assembled a draft genome of Caenorhabditis sp. 3 PS1010 through a combination of direct sequencing and scaffolding with RNA-seq. We first sequenced genomic DNA and mixed-stage cDNA using paired 75-nt reads from an Illumina GAII. A set of 230 million genomic reads yielded an 80-Mb assembly, with a supercontig N50 of 5.0 kb, covering 90% of 429 kb from previously published genomic contigs. Mixed-stage poly(A)+ cDNA gave 47.3 million mappable 75-mers (including 5.1 million spliced reads), which separately assembled into 17.8 Mb of cDNA, with an N50 of 1.06 kb. By further scaffolding our genomic supercontigs with cDNA, we increased their N50 to 9.4 kb, nearly double the average gene size in C. elegans. We predicted 22,851 protein-coding genes, and detected expression in 78% of them. Multigenome alignment and data filtering identified 2672 DNA elements conserved between PS1010 and C. elegans that are likely to encode regulatory sequences or previously unknown ncRNAs. Genomic and cDNA sequencing followed by joint assembly is a rapid and useful strategy for biological analysis.

Global analysis of trans-splicing in Drosophila

Abstract: Precursor mRNA (pre-mRNA) splicing can join exons contained on either a single pre-mRNA (cis) or on separate pre-mRNAs (trans). It is exceedingly rare to have trans-splicing between protein-coding exons and has been demonstrated for only two Drosophila genes: mod(mdg4) and lola. It has also been suggested that trans-splicing is a mechanism for the generation of chimeric RNA products containing sequence from multiple distant genomic sites. Because most high-throughput approaches cannot distinguish cis- and trans-splicing events, the extent to which trans-splicing occurs between protein-coding exons in any organism is unknown. Here, we used paired-end deep sequencing of mRNA to identify genes that undergo trans-splicing in Drosophila interspecies hybrids. We did not observe credible evidence for the existence of chimeric RNAs generated by trans-splicing of RNAs transcribed from distant genomic loci. Rather, our data suggest that experimental artifacts are the source of most, if not all, apparent chimeric RNA products. We did, however, identify 80 genes that appear to undergo trans-splicing between homologous alleles and can be classified into three categories based on their organization: (i) genes with multiple 3′ terminal exons, (ii) genes with multiple first exons, and (iii) genes with very large introns, often containing other genes. Our results suggest that trans-splicing between homologous alleles occurs more commonly in Drosophila than previously believed and may facilitate expression of architecturally complex genes.

Molecular diversification of peptide toxins from the tarantula Haplopelma hainanum (Ornithoctonus hainana) venom based on transcriptomic, peptidomic, and genomic analyses.

Abstract: The tarantula Haplopelma hainanum (Ornithoctonus hainana) is a very venomous spider found widely in the hilly areas of Hainan province in southern China. Its venom contains a variety of toxic components with different pharmacological properties. In the present study, we used a venomic strategy for high-throughput identification of tarantula-venom peptides from H. hainanum. This strategy includes three different approaches: (i) transcriptomics, that is, EST-based cloning and PCR-based cloning plus DNA sequencing; (ii) peptidomics, that is, off-line multiple dimensional liquid chromatography coupled with mass spectrometry (MDLC-MS) plus peptide sequencing (direct Edman sequencing and bottom-up mass spectrometric sequencing); (iii) genomics, that is, genomic DNA cloning plus DNA sequencing. About 420 peptide toxins were detected by mass spectrometry, and 272 peptide precursors were deduced from cDNA and genomic DNA sequences. After redundancy removal, 192 mature sequences were identified by three approaches. This is the largest number of peptide toxin sequences identified from a spider species so far. On the basis of precursor sequence identity, peptide toxins from the tarantula H. hainanum venom can be classified into 11 superfamilies (and related families). Our results revealed that gene duplication and focal hypermutation may be responsible for the enormous molecular diversity in spider peptide toxins. The current work is an initial overview for the study of tarantula-venom peptides in parallel transcriptomic, peptidomic, and genomic analyses. It is hoped that this work will also provide an effective guide for high-throughput identification of peptide toxins from other spider species, especially tarantula species.

Fluorescent conjugated polymer-based FRET technique for detection of DNA methylation of cancer cells.

Abstract: This protocol describes a homogeneous, convenient and sensitive DNA methylation detection method, using an optically amplifying cationic conjugated polymer (CCP, poly((1,4-phenylene)-2,7-[9,9-bis(6'-N,N,N-trimethyl ammonium)-hexyl fluorene] dibromide)). Genomic DNA from cancer cells is pretreated with a methylation-sensitive restriction endonuclease, followed by PCR amplification in the presence of fluorescein-labeled dNTP and Taq polymerase. The PCR only occurs for methylated DNA. DNA methylation of the gene sequence of interest is detected as a result of the fluorescence resonance energy transfer (FRET) between CCP and fluorescein that is incorporated into DNA. The methylated statuses of the p16, HPP1 and GALR2 promoters of five cancer cell lines (HT29, HepG2, A498, HL60 and M17) were assayed to provide an association study between the cancers and susceptibility genes, which shows great potential for early cancer diagnosis. This protocol simplifies previously available procedures by avoiding the need for primer labeling, isolation or purification steps, and sophisticated instruments. The assay takes about 20 h to obtain the methylated statuses of cancer cells.

A unique family of Mrr-like modification-dependent restriction endonucleases

Abstract: Mrr superfamily of homologous genes in microbial genomes restricts modified DNA in vivo. However, their biochemical properties in vitro have remained obscure. Here, we report the experimental characterization of MspJI, a remote homolog of Escherichia coli's Mrr and show it is a DNA modification-dependent restriction endonuclease. Our results suggest MspJI recognizes (m)CNNR (R = G/A) sites and cleaves DNA at fixed distances (N(12)/N(16)) away from the modified cytosine at the 3' side (or N(9)/N(13) from R). Besides 5-methylcytosine, MspJI also recognizes 5-hydroxymethylcytosine but is blocked by 5-glucosylhydroxymethylcytosine. Several other close homologs of MspJI show similar modification-dependent endonuclease activity and display substrate preferences different from MspJI. A unique feature of these modification-dependent enzymes is that they are able to extract small DNA fragments containing modified sites on genomic DNA, for example ∼32 bp around symmetrically methylated CG sites and ∼31 bp around methylated CNG sites. The digested fragments can be directly selected for high-throughput sequencing to map the location of the modification on the genomic DNA. The MspJI enzyme family, with their different recognition specificities and cleavage properties, provides a basis on which many future methods can build to decode the epigenomes of different organisms.

Extensive MHC class II B gene duplication in a passerine, the common Yellowthroat (Geothlypis trichas).

Abstract: The major histocompatibility complex (MHC) is characterized by a birth and death model of evolution involving gene duplication, diversification, loss of function, and deletion. As a result, gene number varies across taxa. Birds have between one and 7 confirmed MHC class II B genes, and the greatest diversity appears to occur in passerines. We used multiple primer sets on both genomic DNA (gDNA) and complementary DNA (cDNA) to characterize the range of class II B genes present in a passerine, the common yellowthroat (Geothlypis trichas). We confirmed 39 exon 2 sequences from gDNA in a single individual, indicating the presence of at least 20 class II B loci. From a second individual, we recovered 16 cDNA sequences belonging to at least 8 transcribed loci. Phylogenetic analysis showed that common yellowthroat sequences fell into subgroups consisting of classical loci, as well as at least 4 different clusters of sequences with reduced sequence variability that may represent pseudogenes or nonclassical loci. Data from 2 additional common yellowthroats demonstrated high interindividual variability. Our results reveal that some passerines possess an extraordinary diversity of MHC gene duplications, including both classical and nonclassical loci.