DNA sequencing by synthesis (SBS) on a solid surface during polymerase reaction can decipher many sequences in parallel. We report here a DNA sequencing method that is a hybrid between the Sanger dideoxynucleotide terminating reaction and SBS. In this approach, four nucleotides, modified as reversible terminators by capping the 3-OH with a small reversible moiety so that they are still recognized by DNA polymerase as substrates, are combined with four cleavable fluorescent dideoxynucleotides to perform SBS. The ratio of the two sets of nucleotides is adjusted as the extension cycles proceed. Sequences are determined by the unique fluorescence emission of each fluorophore on the DNA products terminated by ddNTPs. On removing the 3-OH capping group from the DNA products generated by incorporating the 3-O-modified dNTPs and the fluorophore from the DNA products terminated with the ddNTPs, the polymerase reaction reinitiates to continue the sequence determination. By using an azidomethyl group as a chemically reversible capping moiety in the 3-O-modified dNTPs, and an azido-based cleavable linker to attach the fluorophores to the ddNTPs, we synthesized four 3-O-azidomethyl-dNTPs and four ddNTP-azidolinker-fluorophores for the hybrid SBS. After sequence determination by fluorescence imaging, the 3-O-azidomethyl group and the fluorophore attached to the DNA extension product via the azidolinker are efficiently removed by using Tris(2-carboxyethyl)phosphine in aqueous solution that is compatible with DNA. Various DNA templates, including those with homopolymer regions, were accurately sequenced with a read length of >30 bases by using this hybrid SBS method on a chip and a four-color fluorescence scanner.sequencing by synthesis ͉ DNA chip T he completion of the Human Genome Project (1) was a monumental achievement in biological science. The engine behind this project was the Sanger sequencing method (2), which is still the gold standard in genome research. The prolonged success of the Sanger sequencing method is because of its efficiency and fidelity in producing dideoxy-terminated DNA products that can be separated electrophoretically and detected by fluorescence (3-5). However, a challenge in the use of electrophoresis for DNA separation is the difficulty in achieving high throughput and the complexity involved in the automation, although some level of increased parallelization may be achieved by using miniaturization (6).To overcome the limitations of the Sanger sequencing technology, a variety of new methods have been investigated. Such approaches include sequencing by hybridization (7), mass spectrometry sequencing (8, 9), sequencing by nanopores (10), and sequencing by ligation (11). More recently, DNA sequencing by synthesis (SBS) approaches such as pyrosequencing (12), sequencing of single DNA molecules (13,14), and polymerase colonies (15) have been widely explored. Previously, we reported the development of a general strategy to rationally design cleavable fluorescent nucleotide reversible terminators (NRTs) ...

Background/Aims: Circular RNAs (circRNAs) act as microRNA (miRNA) sponges that regulate gene expression and are involved in physiological and pathological processes. In this study, we evaluated the roles of circRNAs in the chemoresistance of non-small cell lung cancer (NSCLC) to taxol. Methods: High-throughput circRNA microarrays were employed to investigate the circRNA profiles of parental A549 and taxol-resistant A549/Taxol cells. We predicted the miRNA targets of differentially expressed circRNAs via miRNA prediction software and then constructed a circRNA/miRNA network using Cytoscape. Bioinformatics analyses were performed to annotate dysregulated circRNAs in detail. Results: We detected 2909 significantly upregulated and 8372 downregulated circRNAs in A549/Taxol cells compared with A549 cells. The circRNA/miRNA network displayed their interactions, suggesting that circRNAs exert biological effects by absorbing and sequestering miRNA molecules. Computational Gene Ontology and pathway analyses were used to determine the biological function and signaling pathways of host genes of dysregulated circRNAs and to identify potential molecular mechanisms prompting the resistance of NSCLC to taxol. Conclusion: This study focusing on circRNAs related to taxol resistance provides a basis for clarifying the development and progression of drug resistance and for identifying therapeutic targets in NSCLC.

We use methods from Data Mining and Knowledge Discovery to design an algorithm for detecting motifs in protein sequences. The algorithm assumes that a motif is constituted by the presence of a "good" combination of residues in appropriate locations of the motif. The algorithm attempts to compile such good combinations into a "pattern dictionary" by processing an aligned training set of protein sequences. The dictionary is subsequently used to detect motifs in new protein sequences. Statistical significance of the detection results are ensured by statistically determining the various parameters of the algorithm. Based on this approach, we have implemented a program called GYM. The Helix-Turn-Helix motif was used as a model system on which to test our program. The program was also extended to detect Homeodomain motifs. The detection results for the two motifs compare favorably with existing programs. In addition, the GYM program provides a lot of useful information about a given protein sequence.

Study Objective To determine if mutations in NELF, a gene isolated from migratory GnRH neurons, cause normosmic idiopathic hypogonadotropic hypogonadism (IHH) and Kallmann syndrome (KS) Design Molecular analysis correlated with phenotype Setting Academic medical center Patients 168 IHH/KS patients along with unrelated controls were studied for NELF mutations. Intervention NELF coding regions/splice junctions were subjected to PCR-based DNA sequencing, Eleven additional IHH/KS genes were sequenced in three patients with NELF mutations. Main Outcome Measure Mutations were confirmed by SIFT, RT-PCR, and western blot analysis. Results Three novel NELF mutations absent in 372-ethnically matched controls were identified in 3/168(1.8%) IHH/KS patients. One IHH patient had compound heterozygous NELF mutations (c.629-21C>G and c.629-23G>C); and he did not have mutations in 11 other known IHH/KS genes. Two unrelated KS patients had heterozygous NELF mutations and mutation in a second gene: NELF/KAL1 (c.757G>A; p.Ala253Thr of NELF and c.488_490delGTT; p.Cys163del of KAL1) and NELF/TACR3 (c. 1160-13C>T of NELF and c.824G>A; p.Trp275X of TACR3). In vitro evidence of these NELF mutations included reduced protein expression and splicing defects. Conclusions Our findings suggest that NELF is associated with normosmic IHH and KS, either singly or in combination with a mutation in another gene.