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What's the best way to find all the possible cutting sites of an sequence-specific enzyme?
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5.2 years ago
zhuxun2 • 20
United States

I have an sequence-specific enzyme for cutting the DNA. The enzyme recognize a fixed 6bps sequence (e.g. ACTAGT) and cut both strands of the DNA at a specific location (e.g. A|CTAGT).

I was wondering if there is a way I can find out all the locations of possible cutting sites in the genome. That is, I'm looking for the location of all the sequence "ACTAGT" (perfect match only) along the entire genome.

I have the FASTA files from each of the chromosome (chr1.fa, chr2.fa, etc.), from hg19 database.

I considered using Bowtie2, with "-a" option, but after reading the manual I think the program was not designed for this purpose and they warned that "it could be extremely slow". I was thinking if there is a (possibly lightweight) program that was designed specifically for this.

Thank you.

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A RegEx in Perl/Python should work fine, BioPerl/BioPython included functions for this.

Something like this:

#!/usr/bin/perl
# restriction.pl
my $site = "ACTAGT"; # This is palindromic, no rev-comp sequence needed

$/ = "\n>"; # Fasta slurp-mode
while (<>) {
    s/>//g;
    my ($id, @seq) = split (/\n/, $_);
    my $seq = join "", @seq;
    while ($seq =~ m/$site/g) {
        print "$id -> $-[0]\n";
    }
}

and run: perl restriction.pl < FASTA > SITES

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In case this is a homework question, for extra marks, you might want to consider how polymorphisms could affect the result.

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Even more embarrassingly, it is not. :D

By polymorphism you mean SNPs on the genome? Or on the enzyme?

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Don't forget to ask how do position and GC-content mutation frequency affects the sites too.

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2.2 years ago
Neilfws 48k
Sydney, Australia

EMBOSS. Lots and lots of useful, small command-line utilities including several for nucleic acid restriction.

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Re-reading the question, a string/regex search as suggested by JC is a good solution. However, the EMBOSS tools certainly fit the description "a (possibly lightweight) program that was designed specifically for this."

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You right, you can use Emboss::restrict to get the RE mapping, but could be faster a little script rather than install Emboss ;)

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20 months ago
Gary • 450
Taiwan/Taichung/China Medical Universit…

Hi,

A|CTAGT is the SpeI cutting site. You can use UCSC Genome Browser to show SpeI cutting on the whole genome level as the fig1. On the UCSC Genome Browser, please press Restr_Enzymes track and key in SpeI under the Filter display by enzyme as the fig2.

In addition, the free version of SnapGene also can do the same thing (http://www.snapgene.com/). SnapGene is user-friendly and its results are very beautiful, since it is commercial software.

fig1

fig2

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