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Magasin J.D.,University of California at Santa Cruz | Gerloff D.L.,Foundation for Applied Molecular Evolution FfAME
Bioinformatics | Year: 2014

Motivation: Despite advances in high-throughput sequencing, marine metagenomic samples remain largely opaque. A typical sample contains billions of microbial organisms from thousands of genomes and quadrillions of DNA base pairs. Its derived metagenomic dataset underrepresents this complexity by orders of magnitude because of the sparseness and shortness of sequencing reads. Read shortness and sequencing errors pose a major challenge to accurate species and functional annotation. This includes distinguishing known from novel species. Often the majority of reads cannot be annotated and thus cannot help our interpretation of the sample. Results: Here, we demonstrate quantitatively how careful assembly of marine metagenomic reads within, but also across, datasets can alleviate this problem. For 10 simulated datasets, each with species complexity modeled on a real counterpart, chimerism remained within the same species for most contigs (97%). For 42 real pyrosequencing ('454') datasets, assembly increased the proportion of annotated reads, and even more so when datasets were pooled, by on average 1.6% (max 6.6%) for species, 9.0% (max 28.7%) for Pfam protein domains and 9.4% (max 22.9%) for PANTHER gene families. Our results outline exciting prospects for data sharing in the metagenomics community. While chimeric sequences should be avoided in other areas of metagenomics (e.g. biodiversity analyses), conservative pooled assembly is advantageous for annotation specificity and sensitivity. Intriguingly, our experiment also found potential prospects for (low-cost) discovery of new species in 'old' data. © The Author 2014. Published by Oxford University Press. All rights reserved.

Schein C.H.,Foundation for Applied Molecular Evolution FfAME | Ye M.,University of Texas Medical Branch | Paul A.V.,State University of New York at Stony Brook | Oberste M.S.,Centers for Disease Control and Prevention | And 4 more authors.
Virology | Year: 2015

Enteroviruses (EV) uridylylate a peptide, VPg, as the first step in their replication. VPgpUpU, found free in infected cells, serves as the primer for RNA elongation. The abilities of four polymerases (3Dpol), from EV-species A-C, to uridylylate VPgs that varied by up to 60% of their residues were compared. Each 3Dpol was able to uridylylate all five VPgs using polyA RNA as template, while showing specificity for its own genome encoded peptide. All 3Dpol uridylylated a consensus VPg representing the physical chemical properties of 31 different VPgs. Thus the residues required for uridylylation and the enzymatic mechanism must be similar in diverse EV. As VPg-binding sites differ in co-crystal structures, the reaction is probably done by a second 3Dpol molecule. The conservation of polymerase residues whose mutation reduces uridylylation but not RNA elongation is compared. © 2015 Elsevier Inc.

Kim H.-J.,Foundation for Applied Molecular Evolution FfAME | Kim H.-J.,Westheimer Institute for Science and Technology TWIST | Chen F.,Foundation for Applied Molecular Evolution FfAME | Chen F.,Westheimer Institute for Science and Technology TWIST | And 3 more authors.
Journal of Organic Chemistry | Year: 2012

6-Aminopyridin-2-ones form Watson-Crick pairs with complementary purine analogues to add a third nucleobase pair to DNA and RNA, if an electron-withdrawing group at position 5 slows oxidation and epimerization. In previous work with a nucleoside analogue trivially named dZ, the electron withdrawing unit was a nitro group. Here, we describe an analogue of dZ (cyano-dZ) having a cyano group instead of a nitro group, including its synthesis, pK a, rates of acid-catalyzed epimerization, and enzymatic incorporation. © 2012 American Chemical Society.

Kim H.-J.,Foundation for Applied Molecular Evolution FfAME | Kim H.-J.,Firebird Biomolecular Sciences, LLC | Leal N.A.,Foundation for Applied Molecular Evolution FfAME | Leal N.A.,Firebird Biomolecular Sciences, LLC | And 4 more authors.
Journal of Organic Chemistry | Year: 2014

Rearranging hydrogen bonding groups adds nucleobases to an artificially expanded genetic information system (AEGIS), pairing orthogonally to standard nucleotides. We report here a large-scale synthesis of the AEGIS nucleotide carrying 2-amino-3-nitropyridin-6-one (trivially Z) via Heck coupling and a hydroboration/oxidation sequence. RiboZ is more stable against epimerization than its 2′-deoxyribo analogue. Further, T7 RNA polymerase incorporates ZTP opposite its Watson-Crick complement, imidazo[1,2-a]-1,3,5-triazin-4(8H)one (trivially P), laying grounds for using this "second-generation" AEGIS Z:P pair to add amino acids encoded by mRNA. © 2014 American Chemical Society.

Yang Z.,Foundation for Applied Molecular Evolution FfAME | Durante M.,University of Miami | Glushakova L.G.,Foundation for Applied Molecular Evolution FfAME | Sharma N.,Foundation for Applied Molecular Evolution FfAME | And 5 more authors.
Analytical Chemistry | Year: 2013

Methods to detect DNA and RNA (collectively xNA) are easily plagued by noise, false positives, and false negatives, especially with increasing levels of multiplexing in complex assay mixtures. Here, we describe assay architectures that mitigate these problems by converting standard xNA analyte sequences into sequences that incorporate nonstandard nucleotides (Z and P). Z and P are extra DNA building blocks that form tight nonstandard base pairs without cross-binding to natural oligonucleotides containing G, A, C, and T (GACT). The resulting improvements are assessed in an assay that inverts the standard Luminex xTAG architecture, placing a biotin on a primer (rather than on a triphosphate). This primer is extended on the target to create a standard GACT extension product that is captured by a CTGA oligonucleotide attached to a Luminex bead. By using conversion, a polymerase incorporates dZTP opposite template dG in the absence of dCTP. This creates a Z-containing extension product that is captured by a bead-bound oligonucleotide containing P, which binds selectively to Z. The assay with conversion produces higher signals than the assay without conversion, possibly because the Z/P pair is stronger than the C/G pair. These architectures improve the ability of the Luminex instruments to detect xNA analytes, producing higher signals without the possibility of competition from any natural oligonucleotides, even in complex biological samples. © 2013 American Chemical Society.

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