est2genome

 

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Function

Align EST sequences to genomic DNA sequence

Description

est2genome aids the prediction of genes by sequence homology. It aligns a set of spliced nucleotide sequences (ESTs cDNAs or mRNAs) to an unspliced genomic DNA sequence, inserting introns of arbitrary length when needed. Where feasible introns start and stop at the splice consensus dinucleotides GT and AG.

By default, est2genome makes three alignments: First it compares both strands of the spliced sequence against the forward strand of the genomic sequence, assuming the splice consensus GT/AG (ie in the forward gene direction). The maximum-scoring orientation is then realigned assuming the splice consensus CT/AC (ie in the reversed gene direction). By default, only the overall maximum-scoring alignment is reported, and then if it scores higher than a specific minimum threshold score. Optionally, all comparisons may be reported.

The program outputs a list of the exons and introns it has found. The format is like that of MSPcrunch, ie a list of matching segments. This format is easy to parse into other software. The program also indicates, based on the splice site information, the gene's predicted direction of transcription. Optionally the full sequence alignment is printed as well.

Algorithm

The program uses a linear-space divide-and-conquer strategy (Myers and Miller, 1988; Huang, 1994) to limit memory use: 1. A first pass Smith-Waterman local alignment scan is done to find the start, end and score of the maximally scoring segments (including introns of course). No other alignment information is retained. 2. Subsequences corresponding to these segments are extracted 3a. If the product of the subsequences' lengths is less than a user-defined threshold (-space parameter), i.e. they will fit in memory, the segments are realigned using the Needleman-Wunsch global alignment algorithm, which will give the same result as the Smith-Waterman since the subsequences are guaranteed to align end-to-end. 3b. If the product of the lengths exceeds the threshold (a full alignment will not fit in memory) the alignment is made recursively by splitting the spliced (EST) sequence in half and finding the genome sequence position which aligns with the EST mid-point. The process is repeated until the product of the lengths is less than the threshold. The problem reduces to aligning the left-hand and right-hand portions of the sequences separately and merging the result. 4. The genome sequence is searched against the forward and reverse strands of the spliced (EST) sequence, assuming a forward gene splicing direction (i.e. GT/AG consensus). 5. Then the best-scoring orientation is realigned assuming reverse splicing (CT/AC consensus). The overall best alignment is reported. The worst-case run-time for the algorithm is about 3 times as long as would be taken to align using a quadratic-space program. In practice the maximal-scoring segment is often much shorter than the full genome length so the program runs only about 1.5 times slower.

The algorithm has the following steps:

  1. A first-pass Smith-Waterman scan is done to locate the score, start and end of the maximal scoring segment (including introns of course). No other alignment information is retained.
  2. Subsequences corresponding to the maximal-scoring segments are extracted. If the product of these subsequences' lengths is less than the area parameter then the segments are re-aligned using the Needleman-Wunsch algorithm, which in this instance will give the same result as the Smith-Waterman since they are guaranteed to align end-to-end.
  3. If the product of lengths exceeds the area threshold then the alignment is recursively broken down by splitting the EST in half and finding the genome position which aligns with the EST mid-point. The problem then reduces to aligning the left-hand and right-hand portions of the sequences separately and merging the result.
The worst-case run-time for the algorithm is about 3 times as long as would be taken to align using a quadratic-space program. In practice the maximal-scoring segment is often much shorter than the full genome length so the program runs only about 1.5 times slower.

Usage

Here is a sample session with est2genome


% est2genome 
Align EST sequences to genomic DNA sequence
Spliced EST nucleotide sequence(s): tembl:h45989
Unspliced genomic nucleotide sequence: tembl:z69719
Output file [h45989.est2genome]: 

Go to the input files for this example
Go to the output files for this example

Command line arguments

   Standard (Mandatory) qualifiers:
  [-estsequence]       seqall     Spliced EST nucleotide sequence(s)
  [-genomesequence]    sequence   Unspliced genomic nucleotide sequence
  [-outfile]           outfile    [*.est2genome] Output file name

   Additional (Optional) qualifiers:
   -match              integer    [1] Score for matching two bases (Any
                                  integer value)
   -mismatch           integer    [1] Cost for mismatching two bases (Any
                                  integer value)
   -gappenalty         integer    [2] Cost for deleting a single base in
                                  either sequence, excluding introns (Any
                                  integer value)
   -intronpenalty      integer    [40] Cost for an intron, independent of
                                  length. (Any integer value)
   -splicepenalty      integer    [20] Cost for an intron, independent of
                                  length and starting/ending on donor-acceptor
                                  sites (Any integer value)
   -minscore           integer    [30] Exclude alignments with scores below
                                  this threshold score. (Any integer value)

   Advanced (Unprompted) qualifiers:
   -reverse            boolean    Reverse the orientation of the EST sequence
   -[no]usesplice      boolean    [Y] Use donor and acceptor splice sites. If
                                  you want to ignore donor-acceptor sites then
                                  set this to be false.
   -mode               menu       [both] This determines the comparion mode.
                                  The default value is 'both', in which case
                                  both strands of the est are compared
                                  assuming a forward gene direction (ie GT/AG
                                  splice sites), and the best comparsion
                                  redone assuming a reversed (CT/AC) gene
                                  splicing direction. The other allowed modes
                                  are 'forward', when just the forward strand
                                  is searched, and 'reverse', ditto for the
                                  reverse strand. (Values: both (Both
                                  strands); forward (Forward strand only);
                                  reverse (Reverse strand only))
   -[no]best           boolean    [Y] You can print out all comparisons
                                  instead of just the best one by setting this
                                  to be false.
   -space              float      [10.0] For linear-space recursion. If
                                  product of sequence lengths divided by 4
                                  exceeds this then a divide-and-conquer
                                  strategy is used to control the memory
                                  requirements. In this way very long
                                  sequences can be aligned.
                                  If you have a machine with plenty of memory
                                  you can raise this parameter (but do not
                                  exceed the machine's physical RAM) (Any
                                  numeric value)
   -shuffle            integer    [0] Shuffle (Any integer value)
   -seed               integer    [20825] Random number seed (Any integer
                                  value)
   -align              boolean    Show the alignment. The alignment includes
                                  the first and last 5 bases of each intron,
                                  together with the intron width. The
                                  direction of splicing is indicated by angle
                                  brackets (forward or reverse) or ????
                                  (unknown).
   -width              integer    [50] Alignment width (Any integer value)

   Associated qualifiers:

   "-estsequence" associated qualifiers
   -sbegin1            integer    Start of each sequence to be used
   -send1              integer    End of each sequence to be used
   -sreverse1          boolean    Reverse (if DNA)
   -sask1              boolean    Ask for begin/end/reverse
   -snucleotide1       boolean    Sequence is nucleotide
   -sprotein1          boolean    Sequence is protein
   -slower1            boolean    Make lower case
   -supper1            boolean    Make upper case
   -sformat1           string     Input sequence format
   -sdbname1           string     Database name
   -sid1               string     Entryname
   -ufo1               string     UFO features
   -fformat1           string     Features format
   -fopenfile1         string     Features file name

   "-genomesequence" associated qualifiers
   -sbegin2            integer    Start of the sequence to be used
   -send2              integer    End of the sequence to be used
   -sreverse2          boolean    Reverse (if DNA)
   -sask2              boolean    Ask for begin/end/reverse
   -snucleotide2       boolean    Sequence is nucleotide
   -sprotein2          boolean    Sequence is protein
   -slower2            boolean    Make lower case
   -supper2            boolean    Make upper case
   -sformat2           string     Input sequence format
   -sdbname2           string     Database name
   -sid2               string     Entryname
   -ufo2               string     UFO features
   -fformat2           string     Features format
   -fopenfile2         string     Features file name

   "-outfile" associated qualifiers
   -odirectory3        string     Output directory

   General qualifiers:
   -auto               boolean    Turn off prompts
   -stdout             boolean    Write first file to standard output
   -filter             boolean    Read first file from standard input, write
                                  first file to standard output
   -options            boolean    Prompt for standard and additional values
   -debug              boolean    Write debug output to program.dbg
   -verbose            boolean    Report some/full command line options
   -help               boolean    Report command line options. More
                                  information on associated and general
                                  qualifiers can be found with -help -verbose
   -warning            boolean    Report warnings
   -error              boolean    Report errors
   -fatal              boolean    Report fatal errors
   -die                boolean    Report dying program messages

Standard (Mandatory) qualifiers Allowed values Default
[-estsequence]
(Parameter 1)
Spliced EST nucleotide sequence(s) Readable sequence(s) Required
[-genomesequence]
(Parameter 2)
Unspliced genomic nucleotide sequence Readable sequence Required
[-outfile]
(Parameter 3)
Output file name Output file <*>.est2genome
Additional (Optional) qualifiers Allowed values Default
-match Score for matching two bases Any integer value 1
-mismatch Cost for mismatching two bases Any integer value 1
-gappenalty Cost for deleting a single base in either sequence, excluding introns Any integer value 2
-intronpenalty Cost for an intron, independent of length. Any integer value 40
-splicepenalty Cost for an intron, independent of length and starting/ending on donor-acceptor sites Any integer value 20
-minscore Exclude alignments with scores below this threshold score. Any integer value 30
Advanced (Unprompted) qualifiers Allowed values Default
-reverse Reverse the orientation of the EST sequence Boolean value Yes/No No
-[no]usesplice Use donor and acceptor splice sites. If you want to ignore donor-acceptor sites then set this to be false. Boolean value Yes/No Yes
-mode This determines the comparion mode. The default value is 'both', in which case both strands of the est are compared assuming a forward gene direction (ie GT/AG splice sites), and the best comparsion redone assuming a reversed (CT/AC) gene splicing direction. The other allowed modes are 'forward', when just the forward strand is searched, and 'reverse', ditto for the reverse strand.
both (Both strands)
forward (Forward strand only)
reverse (Reverse strand only)
both
-[no]best You can print out all comparisons instead of just the best one by setting this to be false. Boolean value Yes/No Yes
-space For linear-space recursion. If product of sequence lengths divided by 4 exceeds this then a divide-and-conquer strategy is used to control the memory requirements. In this way very long sequences can be aligned. If you have a machine with plenty of memory you can raise this parameter (but do not exceed the machine's physical RAM) Any numeric value 10.0
-shuffle Shuffle Any integer value 0
-seed Random number seed Any integer value 20825
-align Show the alignment. The alignment includes the first and last 5 bases of each intron, together with the intron width. The direction of splicing is indicated by angle brackets (forward or reverse) or ???? (unknown). Boolean value Yes/No No
-width Alignment width Any integer value 50

Input file format

est2genome reads two nucleotide sequences. The first is an EST sequence (a single read or a finished cDNA). The second is a genomic finished sequence.

Input files for usage example

'tembl:h45989' is a sequence entry in the example nucleic acid database 'tembl'

Database entry: tembl:h45989

ID   H45989; SV 1; linear; mRNA; EST; HUM; 495 BP.
XX
AC   H45989;
XX
DT   18-NOV-1995 (Rel. 45, Created)
DT   04-MAR-2000 (Rel. 63, Last updated, Version 2)
XX
DE   yo13c02.s1 Soares adult brain N2b5HB55Y Homo sapiens cDNA clone
DE   IMAGE:177794 3', mRNA sequence.
XX
KW   EST.
XX
OS   Homo sapiens (human)
OC   Eukaryota; Metazoa; Chordata; Craniata; Vertebrata; Euteleostomi; Mammalia;
OC   Eutheria; Euarchontoglires; Primates; Haplorrhini; Catarrhini; Hominidae;
OC   Homo.
XX
RN   [1]
RP   1-495
RA   Hillier L., Clark N., Dubuque T., Elliston K., Hawkins M., Holman M.,
RA   Hultman M., Kucaba T., Le M., Lennon G., Marra M., Parsons J., Rifkin L.,
RA   Rohlfing T., Soares M., Tan F., Trevaskis E., Waterston R., Williamson A.,
RA   Wohldmann P., Wilson R.;
RT   "The WashU-Merck EST Project";
RL   Unpublished.
XX
DR   GDB; 3839990.
DR   GDB; 4193257.
DR   ImaGenes; ENSEp780A0214D.
DR   ImaGenes; ENSEp780A044Q.
DR   ImaGenes; HU3_p972A0639D.
DR   ImaGenes; HU3_p972B1110Q.
DR   ImaGenes; HU3_p983A0639D.
DR   ImaGenes; HU4_p940A0622D.
DR   ImaGenes; IMAGp956A0431Q.
DR   ImaGenes; IMAGp998F03326Q.
DR   ImaGenes; RZPDp1096A101D.
DR   ImaGenes; RZPDp1096A191Q.
DR   ImaGenes; RZPDp200A0214D.
DR   UNILIB; 555; 300.
XX
CC   On May 8, 1995 this sequence version replaced gi:800819.
CC   Contact: Wilson RK
CC   Washington University School of Medicine
CC   4444 Forest Park Parkway, Box 8501, St. Louis, MO 63108
CC   Tel: 314 286 1800
CC   Fax: 314 286 1810
CC   Email: est@watson.wustl.edu
CC   Insert Size: 544
CC   High quality sequence stops: 265
CC   Source: IMAGE Consortium, LLNL
CC   This clone is available royalty-free through LLNL ; contact the
CC   IMAGE Consortium (info@image.llnl.gov) for further information.
CC   Possible reversed clone: polyT not found
CC   Insert Length: 544   Std Error: 0.00
CC   Seq primer: SP6
CC   High quality sequence stop: 265.
XX
FH   Key             Location/Qualifiers
FH
FT   source          1..495
FT                   /organism="Homo sapiens"
FT                   /lab_host="DH10B (ampicillin resistant)"
FT                   /mol_type="mRNA"
FT                   /sex="Male"
FT                   /dev_stage="55-year old"
FT                   /clone_lib="Soares adult brain N2b5HB55Y"
FT                   /clone="IMAGE:177794"
FT                   /note="Organ: brain; Vector: pT7T3D (Pharmacia) with a
FT                   modified polylinker; Site_1: Not I; Site_2: Eco RI; 1st
FT                   strand cDNA was primed with a Not I - oligo(dT) primer [5'
FT                   TGTTACCAATCTGAAGTGGGAGCGGCCGCGCTTTTTTTTTTTTTTTTTTT 3'],
FT                   double-stranded cDNA was size selected, ligated to Eco RI
FT                   adapters (Pharmacia), digested with Not I and cloned into
FT                   the Not I and Eco RI sites of a modified pT7T3 vector
FT                   (Pharmacia). Library went through one round of
FT                   normalization to a Cot = 53. Library constructed by Bento
FT                   Soares and M.Fatima Bonaldo. The adult brain RNA was
FT                   provided by Dr. Donald H. Gilden. Tissue was acquired 17-18
FT                   hours after death which occurred in consequence of a
FT                   ruptured aortic aneurysm. RNA was prepared from a pool of
FT                   tissues representing the following areas of the brain:
FT                   frontal, parietal, temporal and occipital cortex from the
FT                   left and right hemispheres, subcortical white matter, basal
FT                   ganglia, thalamus, cerebellum, midbrain, pons and medulla."
FT                   /db_xref="taxon:9606"
FT                   /db_xref="UNILIB:555"
XX
SQ   Sequence 495 BP; 73 A; 135 C; 169 G; 104 T; 14 other;
     ccggnaagct cancttggac caccgactct cgantgnntc gccgcgggag ccggntggan        60
     aacctgagcg ggactggnag aaggagcaga gggaggcagc acccggcgtg acggnagtgt       120
     gtggggcact caggccttcc gcagtgtcat ctgccacacg gaaggcacgg ccacgggcag       180
     gggggtctat gatcttctgc atgcccagct ggcatggccc cacgtagagt ggnntggcgt       240
     ctcggtgctg gtcagcgaca cgttgtcctg gctgggcagg tccagctccc ggaggacctg       300
     gggcttcagc ttcccgtagc gctggctgca gtgacggatg ctcttgcgct gccatttctg       360
     ggtgctgtca ctgtccttgc tcactccaaa ccagttcggc ggtccccctg cggatggtct       420
     gtgttgatgg acgtttgggc tttgcagcac cggccgccga gttcatggtn gggtnaagag       480
     atttgggttt tttcn                                                        495
//

Database entry: tembl:z69719

ID   Z69719; SV 1; linear; genomic DNA; STD; HUM; 33760 BP.
XX
AC   Z69719;
XX
DT   26-FEB-1996 (Rel. 46, Created)
DT   13-JAN-2009 (Rel. 99, Last updated, Version 7)
XX
DE   Human DNA sequence from clone XX-CNFG9 on chromosome 16
XX
KW   C16orf33; HTG; POLR3K; RHBDF1.
XX
OS   Homo sapiens (human)
OC   Eukaryota; Metazoa; Chordata; Craniata; Vertebrata; Euteleostomi; Mammalia;
OC   Eutheria; Euarchontoglires; Primates; Haplorrhini; Catarrhini; Hominidae;
OC   Homo.
XX
RN   [1]
RP   1-33760
RA   Kershaw J.;
RT   ;
RL   Submitted (09-JAN-2009) to the EMBL/GenBank/DDBJ databases.
RL   Wellcome Trust Sanger Institute, Hinxton, Cambridgeshire, CB10 1SA, UK.
RL   E-mail enquiries: vega@sanger.ac.uk Clone requests: Geneservice
RL   (http://www.geneservice.co.uk/) and BACPAC Resources
RL   (http://bacpac.chori.org/)
XX
DR   EMBL-CON; GL000124.
DR   EMBL-JOIN; Z69720.
DR   GDB; 11502921.
XX
CC   -------------- Genome Center
CC   Center: Wellcome Trust Sanger Institute
CC   Center code: SC
CC   Web site: http://www.sanger.ac.uk
CC   Contact: vega@sanger.ac.uk
CC   --------------
CC   
CC   This sequence was finished as follows unless otherwise noted: all regions
CC   were either double-stranded or sequenced with an alternate chemistry or
CC   covered by high quality data (i.e., phred quality >= 30); an attempt was
CC   made to resolve all sequencing problems, such as compressions and repeats;
CC   all regions were covered by at least one subclone; and the assembly was
CC   confirmed by restriction digest, except on the rare occasion of the clone
CC   being a YAC.
CC   
CC   The following abbreviations are used to associate primary accession
CC   numbers given in the feature table with their source databases:
CC   Em:, EMBL; Sw:, SWISSPROT; Tr:, TREMBL; Wp:, WORMPEP;
CC   Information on the WORMPEP database can be found at
CC   http://www.sanger.ac.uk/Projects/C_elegans/wormpep


  [Part of this file has been deleted for brevity]

     gagacagcag agtgctcagc tcatgaagga ggcaccagcc gccatgcctc tacatccagg     30840
     tctcctgggg ttcccacctc cacaaaaacc cccactgcta ggagtgcagg caggagggga     30900
     cctgagaacc gacagttata ggtcctgcgg gtgggcagtg ctgggtgttc tggtctgccc     30960
     cacccctgtg tgcctagatc cccatctggg cctcaagtgg gtgggattcc aaaggaagag     31020
     ccggagtagg cgtggggagg ggcaggccca ggctggacaa agagtctggc cagggagcgg     31080
     cacattgccc tcccagagac agtggctcag tgtccaggcc ttccccaggc gcacagtggg     31140
     ctcttgttcc cagaaagccc ctcgggggga tccaaacagt gtctccccca ccccgctgac     31200
     ccctcagtgt atggggaaac cgtggcccac ggaaggcctc actgcctggg gtcacacagc     31260
     atctgagtca ctgcagcagc ctcacagctg ccagcccagg cccagcccca tcaggagaca     31320
     cccaaagcca cagtgcatcc caggaccagc tgggggggct gcgggcagga ctctcgatga     31380
     ggctgaggga cgaggagggt caagggagcc actggcgcca tgcatgctga cgtcccctct     31440
     ggctgcctgc agagcctggt gtggaagggc tgagtggggg atggtggaga gtcctgttaa     31500
     ctcaggtttc tgctctgggg atgtctgggc acccatcaag ctggccgcgt gcacaggtgc     31560
     agggagagcc agaaagcagg agccgatgca gggaggccac tggggacagc ccaggctgat     31620
     gcttgggccc catgtgtctc caccacctac aaccctaagc aagcctcagc tttcccatct     31680
     ggaaatcagg ggtcacagca gtgcctggca cagtagcagc ggctgactcc atcacagggt     31740
     ggtgtagcct gtgggtactt ggcactctct gaggggcagg agctgggggg tgaaaggacc     31800
     ctagagcata tgcaacaaga gggcagccct ggggacacct ggggacagaa ccctccaaag     31860
     gtgtcgagtt tgggaagaga ctagagagaa gctctggcca gtccaggcat agacagtggc     31920
     cacagccagt ggagagctgc atcctcaggt gtgagcagca accacctctg tactcaggcc     31980
     tgccctgcac actcacagga ccatgctggc agggacaact ggcggcggag ttgactgcca     32040
     accccggggc cagaaccatc aagcctgggc tctgctccgc ccaaggaact gcctgctgcc     32100
     gaggtcagct ggagcaaggg gcctcacccc gggacacctt cccagacgtg tcctcagctc     32160
     acatgagcct catcccaggg ggatgtggct cctccagcat ccccacccac acgctgctct     32220
     ctgaccctca gtcttctgtt tgactcctaa tctgaagctc aatcctagat ctcccttgag     32280
     aagggggtca ccagctgtct ggcagcccag cctccaggtc ttctggatta atgaagggaa     32340
     agtcacctgg cctctctgcc ttgtctatta atggcatcat gctgagaatg atatttgcta     32400
     ggccctttgc aaaccccaaa gtgctcttca accctcccag tgaagcctct tcttttctgt     32460
     ggaagaaatg aggttcaggg tggagcaggg caggcctgag acctttgcag ggttctctcc     32520
     aggtccccag caggacagac tggcaccctg cctcccctca tcaccctaga caaggagaca     32580
     gaacaagagg ttccctgcta caggccatct gtgagggaag ccgccctagg gcctgtagac     32640
     acaggaatcc ctgaggacct gacctgtgag ggtagtgcac aaaggggcca gcacttggca     32700
     ggaggggggg gggcactgcc ccaaggctca gctagcaaat gtggcacagg ggtcaccaga     32760
     gctaaacccc tgactcagtt gggtctgaca ggggctgaca tggcagacac acccaggaat     32820
     caggggacac caagtgcagc tcagggcacc tgtccaggcc acacagtcag aaaggggatg     32880
     gcagcaagga cttagctaca ctagattctg ggggtaaact gcctggtatg ctggtcactg     32940
     ctagtcccca gtctggagtc tagctgggtc tcaggagtta ggcgaaaaca ccctccccag     33000
     gctgcaggtg ggagaggccc acatcccctg cacacgtctg gccagaggac agatgggcag     33060
     cccagtcacc agtcagagcc ctccagaggt gtccctgact gaccctacac acatgcaccc     33120
     aggtgcccag gcacccttgg gctcagcaac cctgcaaccc cctcccagga cccaccagaa     33180
     gcaggatagg actagagagg ccacaggagg gaaaccaagt cagagcagaa atggcttcgg     33240
     tcctcagcag cctggctcag cttcctcaaa ccagatcctg actgatcaca ctggtctgtc     33300
     taacccctgg gaggggtcct ctgtatccat cttacagata aggaaactga ggctcagaga     33360
     agcccatcac tgcctaaggt cccagggcct ataagggagc tcaaagcctt gggccaggtc     33420
     tgcccaggag ctgcagtgga agggaccctg tctgcagacc cccagaagac aaggcagacc     33480
     acctgggttc ttcagccttg tggctgtgga cggctgtcag acccttctaa gaccccttgc     33540
     cacctgctcc atcaggggca tctcagttga agaaggaagg actcaccccc aaaatcgtcc     33600
     aactcagaaa aaaaggcaga agccaaggaa tccaatcact gggcaaaatg tgatcctggc     33660
     acagacactg aggtggggga actggagccg gtgtggcgga ggccctcaca gccaagagca     33720
     actgggggtg ccctgggcag ggactgtagc tgggaagatc                           33760
//

Output file format

Output files for usage example

File: h45989.est2genome

Note Best alignment is between forward est and forward genome, but splice sites imply REVERSED GENE
Exon       163  91.8 25685 25874 Z69719           1   193 H45989        yo13c02.s1 Soares adult brain N2b5HB55Y Homo sapiens cDNA clone IMAGE:177794 3', mRNA sequence.
-Intron    -20   0.0 25875 26278 Z69719      
Exon       207  98.1 26279 26492 Z69719         194   407 H45989        yo13c02.s1 Soares adult brain N2b5HB55Y Homo sapiens cDNA clone IMAGE:177794 3', mRNA sequence.
-Intron    -20   0.0 26493 27390 Z69719      
Exon        63  86.4 27391 27476 Z69719         408   494 H45989        yo13c02.s1 Soares adult brain N2b5HB55Y Homo sapiens cDNA clone IMAGE:177794 3', mRNA sequence.

Span       393  93.6 25685 27476 Z69719           1   494 H45989        yo13c02.s1 Soares adult brain N2b5HB55Y Homo sapiens cDNA clone IMAGE:177794 3', mRNA sequence.

Segment     14  83.3 25685 25702 Z69719           1    18 H45989        yo13c02.s1 Soares adult brain N2b5HB55Y Homo sapiens cDNA clone IMAGE:177794 3', mRNA sequence.
Segment     28  85.7 25703 25737 Z69719          20    54 H45989        yo13c02.s1 Soares adult brain N2b5HB55Y Homo sapiens cDNA clone IMAGE:177794 3', mRNA sequence.
Segment      4 100.0 25738 25741 Z69719          56    59 H45989        yo13c02.s1 Soares adult brain N2b5HB55Y Homo sapiens cDNA clone IMAGE:177794 3', mRNA sequence.
Segment     13 100.0 25742 25754 Z69719          61    73 H45989        yo13c02.s1 Soares adult brain N2b5HB55Y Homo sapiens cDNA clone IMAGE:177794 3', mRNA sequence.
Segment      4 100.0 25756 25759 Z69719          74    77 H45989        yo13c02.s1 Soares adult brain N2b5HB55Y Homo sapiens cDNA clone IMAGE:177794 3', mRNA sequence.
Segment    110  97.4 25760 25874 Z69719          79   193 H45989        yo13c02.s1 Soares adult brain N2b5HB55Y Homo sapiens cDNA clone IMAGE:177794 3', mRNA sequence.
Segment     37 100.0 26279 26315 Z69719         194   230 H45989        yo13c02.s1 Soares adult brain N2b5HB55Y Homo sapiens cDNA clone IMAGE:177794 3', mRNA sequence.
Segment    162  98.8 26317 26480 Z69719         231   394 H45989        yo13c02.s1 Soares adult brain N2b5HB55Y Homo sapiens cDNA clone IMAGE:177794 3', mRNA sequence.
Segment     12 100.0 26481 26492 Z69719         396   407 H45989        yo13c02.s1 Soares adult brain N2b5HB55Y Homo sapiens cDNA clone IMAGE:177794 3', mRNA sequence.
Segment     16 100.0 27391 27406 Z69719         408   423 H45989        yo13c02.s1 Soares adult brain N2b5HB55Y Homo sapiens cDNA clone IMAGE:177794 3', mRNA sequence.
Segment     10  91.7 27407 27418 Z69719         425   436 H45989        yo13c02.s1 Soares adult brain N2b5HB55Y Homo sapiens cDNA clone IMAGE:177794 3', mRNA sequence.
Segment     19  95.2 27419 27439 Z69719         438   458 H45989        yo13c02.s1 Soares adult brain N2b5HB55Y Homo sapiens cDNA clone IMAGE:177794 3', mRNA sequence.
Segment     24  80.6 27441 27476 Z69719         459   494 H45989        yo13c02.s1 Soares adult brain N2b5HB55Y Homo sapiens cDNA clone IMAGE:177794 3', mRNA sequence.

MSP type segments

There are four types of segment,
  1. each gapped Exon
  2. each Intron (marked with a ? if it does not start GT and end AG)
  3. the complete alignment Span
  4. individual ungapped matching Segments.

The score for Exon segments is the alignment score excluding flanking intron penalties. The Span score is the total including the intron costs.

The coordinates of the genomic sequence always refer to the positive strand, but are swapped if the est has been reversed. The splice direction of Introns are indicated as +Intron (forward, splice sites GT/AG) or -Intron (reverse, splice sites CT/AC), or ?Intron (unknown direction). Segment entries give the alignment as a series of ungapped matching segments.

Full alignment

You get the alignment if the -align switch is set. The alignment includes the first and last 5 bases of each intron, together with the intron width. The direction of splicing is indicated by >>>> (forward) or <<<< (reverse) or ???? (unknown)

Data files

None

Notes

est2genome uses a linear-space dynamic-programming algorithm. It has the following parameters:
parameter               default         description

match                   1               score for matching two bases
mismatch                1               cost for mismatching two bases
gap_penalty             2               cost for deleting a single base in
                                        either sequence, 
                                        excluding introns
intron_penalty          40              cost for an intron, independent of
                                        length.
splice_penalty          20              cost for an intron, independent of
                                        length and starting/ending on
                                        donor-acceptor sites.

space                   10              Space threshold (in  megabytes) 
                                        for linear-space recursion. If the
                                        product of the two sequence 
                                        lengths divided by 4 exceeds this then
                                        a divide-and-conquer strategy is used 
                                        to control the memory requirements. 
                                        In this way very long sequences can
                                        be aligned. 
                                        If you have a machine with plenty of
                                        memory you can raise this parameter
                                        (but do not exceed the machine's
                                        physical RAM)
                                        However, normally you should not need
                                        to change this parameter.
There is no gap initiation cost for short gaps, just a penalty proportional to the length of the gap. Thus the cost of inserting a gap of length L in the EST is
 L*gap_penalty 
and the cost in the genome is
 
min { L*gap_penalty, intron_penalty } or
min { L*gap_penalty, splice_penalty } if the gap starts with GT and ends with AG
                                     (or CT/AC if splice direction reversed)
Introns are not allowed in the EST. The difference between the intron_penalty and splice_penalty allows for some slack in marking the intron end-points. It is often the case that the best intron boundaries, from the point of view of minimising mismatches, will not coincide exactly with the splice consensus, so provided the difference between the intron/splice penalties outweighs the extra mismatch/indel costs the alignment will respect the proper boundaries. If the alignment still prefers boundaries which don't start and end with the splice consensus then this may indicate errors in the sequences.

The default parameters work well, except for very short exons (length less than the splice_penalty, approx) which may be skipped. The intron penalties should not be set to less that the maximum expected random match between the sequences (typically 10-15 bp) in order to avoid spurious matches.

References

  1. Mott R. (1997) EST_GENOME: a program to align spliced DNA sequences to unspliced genomic DNA. Comput. Applic. 13:477-478
  2. Huang X (1994) On global sequence alignment. Comput. Applic. Biosci. 10:227-235.
  3. Myers, EW and Miller, W (1988) Optimal alignments in linear space. Comput. Applic. Biosci. 4:11-17
  4. Smith, TE and Waterman, MS (1981) Identification of common molecular subsequences. J. Mol. Biol. 147:195-197

Warnings

None.

Diagnostic Error Messages

None.

Exit status

It returns 0 unless an error occurs.

Known bugs

None.

See also

Program name Description
needle Needleman-Wunsch global alignment of two sequences
stretcher Needleman-Wunsch rapid global alignment of two sequences

Author(s)

This application was modified for inclusion in EMBOSS by Peter Rice (pmr © ebi.ac.uk)
European Bioinformatics Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge CB10 1SD, UK

The original program was est_genome, written by Richard Mott at the Sanger Centre. The original version is available from ftp://ftp.sanger.ac.uk/pub/pmr/est_genome.4.tar.Z

History

Target users

This program is intended to be used by everyone and everything, from naive users to embedded scripts.

Comments

Thu, 29 Mar 2001

I found est2genome having problems finding very short exons with the default parameters.

With the folowing changes it detects also a 14bp exon correctly:

mismatch 1 -> 3
intronpenalty 40 -> 20
splicepenalty 20 -> 10
minscore 30 -> 10
Dr. David Bauer
GenProfile AG, Max-Delbrueck-Center, Erwin-Negelein-Haus 
Robert-Roessle-Str. 10, D-13125 Berlin, Germany
bauer@genprofile.com, Tel:49-30-94892165, FAX:49-30-94892151