title: Evolutionarily conserved elements in vertebrate, insect, worm, and yeast genomes.
abstract: We have conducted a comprehensive search for conserved elements in vertebrate genomes, using genome-wide multiple alignments of five vertebrate species (human, mouse, rat, chicken, and Fugu rubripes). Parallel searches have been performed with multiple alignments of four insect species (three species of Drosophila and Anopheles gambiae), two species of Caenorhabditis, and seven species of Saccharomyces. Conserved elements were identified with a computer program called phastCons, which is based on a two-state phylogenetic hidden Markov model (phylo-HMM). PhastCons works by fitting a phylo-HMM to the data by maximum likelihood, subject to constraints designed to calibrate the model across species groups, and then predicting conserved elements based on this model. The predicted elements cover roughly 3%-8% of the human genome (depending on the details of the calibration procedure) and substantially higher fractions of the more compact Drosophila melanogaster (37%-53%), Caenorhabditis elegans (18%-37%), and Saccharaomyces cerevisiae (47%-68%) genomes. From yeasts to vertebrates, in order of increasing genome size and general biological complexity, increasing fractions of conserved bases are found to lie outside of the exons of known protein-coding genes. In all groups, the most highly conserved elements (HCEs), by log-odds score, are hundreds or thousands of bases long. These elements share certain properties with ultraconserved elements, but they tend to be longer and less perfectly conserved, and they overlap genes of somewhat different functional categories. In vertebrates, HCEs are associated with the 3' UTRs of regulatory genes, stable gene deserts, and megabase-sized regions rich in moderately conserved noncoding sequences. Noncoding HCEs also show strong statistical evidence of an enrichment for RNA secondary structure.
authors: Center for Biomolecular Science and Engineering, University of California, Santa Cruz, Santa Cruz, California 95064, USA. acs@soe.ucsc.edu
authors: Adam
authors: A
authors: Siepel
authors: Gill
authors: G
authors: Bejerano
authors: Jakob S
authors: JS
authors: Pedersen
authors: Angie S
authors: AS
authors: Hinrichs
authors: Minmei
authors: M
authors: Hou
authors: Kate
authors: K
authors: Rosenbloom
authors: Hiram
authors: H
authors: Clawson
authors: John
authors: J
authors: Spieth
authors: Ladeana W
authors: LW
authors: Hillier
authors: Stephen
authors: S
authors: Richards
authors: George M
authors: GM
authors: Weinstock
authors: Richard K
authors: RK
authors: Wilson
authors: Richard A
authors: RA
authors: Gibbs
authors: W James
authors: WJ
authors: Kent
authors: Webb
authors: W
authors: Miller
authors: David
authors: D
authors: Haussler
mesh_terms: D020413:3' Untranslated Regions; D000818:Animals; D020029:Base Pairing / Q000235:genetics; D001483:Base Sequence; D017173:Caenorhabditis elegans / Q000235:genetics; D017124:Conserved Sequence; D021901:DNA, Intergenic; D019143:Evolution, Molecular; D016678:Genome; D006801:Humans; D007313:Insecta / Q000235:genetics*; D008969:Molecular Sequence Data; D012440:Saccharomyces / Q000235:genetics; D014714:Vertebrates / Q000235:genetics*; D015003:Yeasts / Q000235:genetics*
chemical_list: D020413:3' Untranslated Regions; D021901:DNA, Intergenic