EMBOSS: dreg


Program dreg

Function

regular expression search of a nucleotide sequence

Description

This searches for matches of a regular expression to a nucleic acid sequence.

A regular expression is a way of specifying an ambiguous pattern to search for. Regular expressions are commonly used in some computer programming languages and may be more familiar to some users than to others.

The following is a short guide to regular expressions in EMBOSS:

^
use this at the start of a pattern to insist that the pattern can only match at the start of a sequence. (eg. '^AUG' matches a start codon at the start of the sequence)
$
use this at the end of a pattern to insist that the pattern can only match at the end of a sequence (eg. 'A+$' matches a poly-A sequence at the end of the sequence)
()
groups a pattern. This is commonly used with '|' (eg. '(AUG)|(ATG)' matches either the DNA or RNA form of the initiation codon )
|
This is the OR operator to enable a match to be made to either one pattern OR another. There is no AND operator in this version of regular expressions.

The following quantifier characters specify the number of time that the character before (in this case 'x') matches:

x?
matches 0 or 1 times (ie, '' or 'x')
x*
matches 0 or more times (ie, '' or 'x' or 'xx' or 'xxx', etc)
x+
matches 1 or more times (ie, 'x' or 'xx' or 'xxx', etc)

Quantifiers can follow any of the following types of character specification:

x
any character (ie 'A')
\x
the character after the backslash is used instead of its normal regular expression meaning. This is commonly used to turn off the special meaning of the characters '^$()|?*+[]-.'. It may be especially useful when searching for gap characters in a sequence (eg '\.' matches only a dot character '.')
[xy]
match one of the characters 'x' or 'y'. You may have one or more characters in this set.
[x-z]
match any one of the set of characters starting with 'x' and ending in 'y' in ASCII order (eg '[A-G]' matches any one of: 'A', 'B', 'C', 'D', 'E', 'F', 'G')
[^x-z]
matches anything except any one of the group of characters in ASCII order (eg '[^A-G]' matches anything EXCEPT any one of: 'A', 'B', 'C', 'D', 'E', 'F', 'G')
.
the dot character matches any other character (eg: 'A.G' matches 'AAG', 'AaG', 'AZG', 'A-G' 'A G', etc.)
Combining some of these features gives the example:
'([AGC]+GGG)|(TTTGGG)'
which matches one or more of any one of 'A' or 'G' or 'C' followed by three 'G's or it matches just 'TTTGGG'.

Regular expressions are case-sensitive. The pattern 'AAAA' will not match the sequence 'aaaa'.

Usage

Here is a sample session with dreg.

% dreg
Input sequence: embl:paamir
Output file [paamir.dreg]: 
Regular expression pattern: ggtacc

Command line arguments

   Mandatory qualifiers:
  [-sequence]          seqall     Sequence database USA
  [-outfile]           outfile    Output file name
  [-pattern]           regexp     Regular expression pattern

   Optional qualifiers: (none)
   Advanced qualifiers: (none)

Mandatory qualifiers Allowed values Default
[-sequence]
(Parameter 1)
Sequence database USA Readable sequence(s) Required
[-outfile]
(Parameter 2)
Output file name Output file <sequence>.dreg
[-pattern]
(Parameter 3)
Regular expression pattern Any regular epression pattern is accepted Required
Optional qualifiers Allowed values Default
(none)
Advanced qualifiers Allowed values Default
(none)

Input file format

Any sequence.

Output file format

This is the output from the example run. Sequence embl:paamir begins at a restriction site with the sequence pattern GGTACC.

dreg search of embl:paamir with pattern GGTACC
Matches in PAAMIR
         PAAMIR     1 GGTACC

Data files

Notes

References

Warnings

Regular expressions are case-sensitive. The pattern 'AAAA' will not match the sequence 'aaaa'.

Diagnostic Error Messages

Exit status

Always returns 0.

Known bugs

See also

Program nameDescription
fuzznucNucleic acid pattern search
fuzzproProtein pattern search
fuzztranProtein pattern search after translation
patmatdbSearch a protein sequence with a motif
patmatmotifsSearch a PROSITE motif database with a protein sequence
pregregular expression search of a protein sequence
pscanScans proteins using PRINTS
tfscanScans DNA sequences for transcription factors

Other EMBOSS programs allow you to search for simple patterns and may be easier for the user who has never used regular expressions before:

Author(s)

This application was written by Peter Rice (pmr@sanger.ac.uk) Informatics Division, The Sanger Centre, Wellcome Trust Genome Campus, Hinxton, Cambridge, CB10 1SA, UK.

History

Target users

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

Comments