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How do I extract ORFs from a fasta file into a new fasta file

by Wasp_Guy (Initiate)
on Jul 07, 2013 at 03:47 UTC ( #1042964=perlquestion: print w/replies, xml ) Need Help??

Wasp_Guy has asked for the wisdom of the Perl Monks concerning the following question:

Hi Pearl Monks. In short: I am a Biochemistry Ph.D. student working on a proteomics project. I am new to programming and Perl. I have an assembled RNA-seq fasta file and I need to extract all of the ORFs into a new fasta file that I can use to blast proteome data against. Any advice on how I can proceed would be very appreciated.

The long story: The RNA-seq data I have is a de-novo assembly of illumina data without a reference genome. This file is far to long to open it on my computer let alone go through it by hand. I also have some mass spec data that returned tryptic peptide sequences from the same tissue. I would like to pull out all of the full length CDS with some 5' and 3' UTR info for the proteins I have found in the tissue by mass spec. I have tried simply blasting the peptides against the assembly but I get hits that are not in open reading frames. It is my hope that if I have a database of only ORFs that identification of my peptides transcripts would be easier. I have read Borisz answer to a similar question in node id=473744 back in 2005. I have copied his code below. I believe this is a good place to start, but I would suppose the major difference is that I need to return all the ORFs from tens of thousands of entries as a new fasta file. Thank you for your consideration.
local $_ = $your_input_string; while ( /ATG/g ) { my $start = pos() - 3; if ( /T(?:AA|AG|GA)/g ) { my $stop = pos; print $start, " ", $stop, " ", $stop - $start, " ", substr ($_, $start, $stop - $start), $/; } }

Replies are listed 'Best First'.
Re: How do I extract ORFs from a fasta file into a new fasta file
by Anonymous Monk on Jul 07, 2013 at 04:02 UTC
Re: How do I extract ORFs from a fasta file into a new fasta file
by zork42 (Monk) on Jul 08, 2013 at 01:40 UTC
Re: How do I extract ORFs from a fasta file into a new fasta file
by biohisham (Priest) on Jul 08, 2013 at 08:29 UTC

    "I would like to pull out all of the full length CDS with some 5' and 3' UTR info for the proteins I have found in the tissue by mass spec"

    If I understand you correctly, I will look at the gff/gtf coordinates for the CDs feature and try to obtain that for the specific protein annotation in the gff file, A fastA file may not have these features handy so it maybe not the way to go unless you have an annotated genome somewhere for you to extract this stuff from.

    "I have tried simply blasting the peptides against the assembly but I get hits that are not in open reading frames"

    Maybe because BLAST is a local alignment and search tool, that behavior is totally expected.

    " I would suppose the major difference is that I need to return all the ORFs from tens of thousands of entries as a new fasta file."

    Read the file one line at a time. Maybe something like what follows ?... If you don't have BioPerl installed then certainly there are many other examples on reading fastA file that don't use BioPerl around here

    #UNTESTED CODE TO DEMONSTRATE A WAY AROUND use strict; use warnings; use Bio::SeqIO; my $in = Bio::SeqIO->new(-file =>"FastA.fa", format = "FASTA"); while(my $seq = $in->next_seq){ my $sequence = $seq->seq; #Do something with $sequence my $ORFpattern = "foo"; if($sequence =~ /$ORFpattern/){ #report or anything } }

    "Hi Pearl Monks"

    we are Perl Monks and not Pearl Monks...

    Welcome to the Monastery and good luck....


    David R. Gergen said "We know that second terms have historically been marred by hubris and by scandal." and I am a two y.o. monk today :D, June,12th, 2011...
Re: How do I extract ORFs from a fasta file into a new fasta file
by Anonymous Monk on Jul 07, 2013 at 16:41 UTC

    Forgive me for replying to a question i know nothing about. But you say you are new to programming, and perl, and you found this code somewhere on the internet. I doubt very much that that would be a good place to start. Best regards.

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