Related bifunctional restriction endonuclease-methyltransferase triplets: TspDTI, Tth111II/TthHB27I and TsoI with distinct specificities

<p>Abstract</p> <p>Background</p> <p>We previously defined a family of restriction endonucleases (REases) from <it>Thermus </it>sp., which share common biochemical and biophysical features, such as the fusion of both the nuclease and methyltransferase (MTase) activities in a single polypeptide, cleavage at a distance from the recognition site, large molecular size, modulation of activity by S-adenosylmethionine (SAM), and incomplete cleavage of the substrate DNA. Members include related thermophilic REases with five distinct specificities: TspGWI, TaqII, Tth111II/TthHB27I, TspDTI and TsoI.</p> <p>Results</p> <p>TspDTI, TsoI and isoschizomers Tth111II/TthHB27I recognize different, but related sequences: 5'-ATGAA-3', 5'-TARCCA-3' and 5'-CAARCA-3' respectively. Their amino acid sequences are similar, which is unusual among REases of different specificity. To gain insight into this group of REases, TspDTI, the prototype member of the <it>Thermus </it>sp. enzyme family, was cloned and characterized using a recently developed method for partially cleaving REases.</p> <p>Conclusions</p> <p>TspDTI, TsoI and isoschizomers Tth111II/TthHB27I are closely related bifunctional enzymes. They comprise a tandem arrangement of Type I-like domains, like other Type IIC enzymes (those with a fusion of a REase and MTase domains), e.g. TspGWI, TaqII and MmeI, but their sequences are only remotely similar to these previously characterized enzymes. The characterization of TspDTI, a prototype member of this group, extends our understanding of sequence-function relationships among multifunctional restriction-modification enzymes.</p

Sensitive and accurate analysis of gene expression signatures enabled by oligonucleotide-labelled cDNA

High-throughput RNA sequencing offers a comprehensive analysis of transcriptome complexity origi-nated from regulatory events, such as differential gene expression, alternative polyadenylation and others, and allows the increase in diagnostic capacity and precision. For gene expression profiling applications that do not specifically require information on alternative splicing events, the mRNA 3′ termini counting approach is a cost-effective alternative to whole transcriptome sequencing. Here, we report MTAS-seq (mRNA sequencing via terminator-assisted synthesis) – a novel RNA-seq library pre-paration method directed towards mRNA 3′ termini. We demonstrate the specific enrichment for 3′- terminal regions by simple and quick single-tube protocol with built-in molecular barcoding to enable accurate estimation of transcript abundance. To achieve that, we synthesized oligonucleotide-modified dideoxynucleotides which enable the generation of cDNA libraries at the reverse transcription step. We validated the performance of MTAS-seq on well-characterized reference bulk RNA and further tested it with eukaryotic cell lysates

Advanced preparation of fragment libraries enabled by oligonucleotide-modified 2 ',3 '-dideoxynucleotides

The ever-growing demand for inexpensive, rapid, and accurate exploration of genomes calls for refinement of existing sequencing techniques. The development of next-generation sequencing (NGS) was a revolutionary milestone in genome analysis. While modified nucleotides already were inherent tools in sequencing and imaging, further modification of nucleotides enabled the expansion into even more diverse applications. Herein we describe the design and synthesis of oligonucleotide-tethered 2′,3′-dideoxynucleotide (ddONNTP) terminators bearing universal priming sites attached to the nucleobase, as well as their enzymatic incorporation and performance in read-through assays. In the context of NGS library preparation, the incorporation of ddONNTP fulfills two requirements at once: the fragmentation step is integrated into the workflow and the obtained fragments are readily labeled by platform-specific adapters. DNA polymerases can incorporate ddONNTP nucleotides, as shown by primer extension assays. More importantly, reading through the unnatural linkage during DNA synthesis was demonstrated, with 25-30% efficiency in single-cycle extension

Fusion sequencing via terminator‐assisted synthesis (FTAS‐seq) identifies TMPRSS2 fusion partners in prostate cancer

Genetic rearrangements that fuse an androgen‐regulated promoter area with a protein‐coding portion of an originally androgen‐unaffected gene are frequent in prostate cancer, with the fusion between transmembrane serine protease 2 (TMPRSS2) and ETS transcription factor ERG (ERG) (TMPRSS2‐ERG fusion) being the most prevalent. Conventional hybridization‐ or amplification‐based methods can test for the presence of expected gene fusions, but the exploratory analysis of currently unknown fusion partners is often cost‐prohibitive. Here, we developed an innovative next‐generation sequencing (NGS)‐based approach for gene fusion analysis termed fusion sequencing via terminator‐assisted synthesis (FTAS‐seq). FTAS‐seq can be used to enrich the gene of interest while simultaneously profiling the whole spectrum of its 3′‐terminal fusion partners. Using this novel semi‐targeted RNA‐sequencing technique, we were able to identify 11 previously uncharacterized TMPRSS2 fusion partners and capture a range of TMPRSS2‐ERG isoforms. We tested the performance of FTAS‐seq with well‐characterized prostate cancer cell lines and utilized the technique for the analysis of patient RNA samples. FTAS‐seq chemistry combined with appropriate primer panels holds great potential as a tool for biomarker discovery that can support the development of personalized cancer therapies

Draft genome sequence of the cyanobacterium Aphanizomenon flos-aquae Strain 2012/KM1/D3, isolated from the Curonian Lagoon (Baltic Sea)

We report here the de novo genome assembly of a cyanobacterium, Aphanizomenon flos-aquae strain 2012/KM1/D3, a harmful bloom-forming species in temperate aquatic ecosystems. The genome is 5.7 Mb with a G C content of 38.2%, and it is enriched mostly with genes involved in amino acid and carbohydrate metabolism

UbaLAI is a monomeric Type IIE restriction enzyme

Type II restriction endonucleases (REases) form a large and highly diverse group of enzymes. Even REases specific for a common recognition site often vary in their oligomeric structure, domain organization and DNA cleavage mechanisms. Here we report biochemical and structural characterization of the monomeric restriction endonuclease UbaLAI, specific for the pseudosymmetric DNA sequence 5'-CC/WGG-3' (where W = A/T, and ‘/’ marks the cleavage position). We present a 1.6 Å co-crystal structure of UbaLAI N-terminal domain (UbaLAI-N) and show that it resembles the B3-family domain of EcoRII specific for the 5'-CCWGG-3' sequence. We also find that UbaLAI C-terminal domain (UbaLAI-C) is closely related to the monomeric REase MvaI, another enzyme specific for the 5'-CCWGG-3' sequence. Kinetic studies of UbaLAI revealed that it requires two recognition sites for optimal activity, and, like other type IIE enzymes, uses one copy of a recognition site to stimulate cleavage of a second copy. We propose that during the reaction UbaLAI-N acts as a handle that tethers the monomeric UbaLAI-C domain to the DNA, thereby helping UbaLAI-C to perform two sequential DNA nicking reactions on the second recognition site during a single DNA-binding event. A similar reaction mechanism may be characteristic to other monomeric two-domain REases