Presentation on theme: "Gene Prediction Preliminary Results Computational Genomics February 20, 2012."— Presentation transcript:
Gene Prediction Preliminary Results Computational Genomics February 20, 2012
ab initio Gene Prediction Using Glimmer3, RAST, Prodigal and GenemarkS
Prodigal lack of complexity(no Hidden Markov Model, no Interpolated Markov Model). based on dynamic programming. remains accuracy in high GC content genomes. tends to predict longer genes rather than more genes.
Command line version Syntax: runGeneMarkS The Output folder contains 3 types of files:.out file: contains the default output.faa file: contains the amino acid sequence of the corresponding ORFs in FASTA format.fnn file: contains the nucleotide sequence of the corresponding ORFs in FASTA format
Strand +:normal strand, -:reverse strand Left end: Begin position, Right end: End position Screenshot of the.out file
Glimmer3 A system for finding genes in microbial DNA Works by creating a variable-length Markov model from a training set of genes Using the model to identify all genes in a DNA sequence
Running Glimmer3 2 step progress 1. A probability model of coding sequences must be built called an interpolated context model. – a set of training sequences – 1. genes identified by homology or known genes – 2. from long, overlapping orfs – 3. genes from a highly similar species 2. program is run to analyze the sequences and make gene predictions – Best results require longest possible training set of genes
Glimmer3 programs Long-orfs uses an amino-acid distribution model to filter the set of orfs Extract builds training set from long, nonoverlapping orfs Build-icm build interpolated context model from training sequences Glimmer3 analyze sequences and make predictions
RAST RAST (Rapid Annotation using Subsystem Technology) is a system for annotating bacterial and archaeal genomes. Pipelines- tRNAScan-SE, Glimmer2, and comparing against other prokaryote genes that are universal across species.
First pass filters identify "candidate" tRNA regions of the sequence. tRNAscan and EufindtRNA Further analysis to confirm the initial tRNAprediction. Cove
tRNAscan-SE –B -o -f -m -B : search for bacterial tRNAs This option selects the bacterial covariace model for tRNA analysis, and loosens the search parameters for EufindtRNA to improve detection o f bacterial tRNAs. -o : save final results in Specifiy this option to write results to. -f : save results and tRNA secondary structures to. -m : save statistics summary for run contains the run options selected as well as statistics on the number of tRNAs detected at each phase of the search, search speed, and other statistics.
Output using “–o” parameter Output using “–f” parameter
Working It works using two level of Hidden markov models. The spotter model is constructed from highly conserved loci within a structural alignment of known rRNA sequences. Once the spotter model detects an approximate position of a gene, flanking regions are extracted and parsed to the full model which matches the entire gene. By enabling a two-level approach it is avoided to run a full model through an entire genome sequence allowing faster predictions.
Command line options Rnammer -S (species) –m (molecules) –xml (xml file) –gff (gff file) –h (hmm report file) –f (fasta file) -S : specify the species to use. In out case, it will be bacterial -m : molecules to search for. (ie. Large subunit or small subunit)
Rfam Database Homology Search A collection of RNA families – Non-coding RNA genes – Structured cis-regulatory elements – Self-splicing RNAs WU-BLAST search, and keeps hits with E-value < 1e-5
Rfam Preliminary Results Accession # Total ncRNA # of rRNA # of tRNA / tmRNA # of sRNA Others (RNasep) Sequencing Coverage M1910765104311112 X M1950185145317153 X M211277995217120 X M2162181105416125 X M2163995125329178 X M2170992165421134 X The output format is: Results: 84 Rfam similarity 25970 27512 1477.28 +. evalue=2.08e-50;gc- content=52;id=SSU_rRNA_bacteria.1;model_end=1518;model_start=1;rfam-acc=RF00177;rfam- id=SSU_rRNA_bacteria
Things to be done Get Geneprimp to work since we are having some problems with the installation and the web server takes a long time to process. Get further information required to run other RNA prediction softwares. Compare specific RNA prediction softwares with Rfam predictions.
Leading Biocomputational Tools eQRNA (Rivas and Eddy 2001) RNAz (Washietl et al. 2005; Gruber etal. 2010) sRNAPredict3/SIPHT (Livny et al. 2006, 2008) NAPP (Marchais et al. 2009) Lu, X., H. Goodrich-Blair, et al. (2011). "Assessing computational tools for the discovery of small RNA genes in bacteria." RNA 17(9): 1635-1647 All four approaches use comparative genomics!!