[Bioperl-l] GN line parsing from Uniprot/Swiss-Prot

[Heikki Lehvaslaiho]

There has been an longstanding problem with GN (gene name) line parsing in 
SwissProt format. It has solved in a way that deals with all the complexity 
in that line but unfortunately is not backward compatible. You have to 
upgrade your scripts if you use bioperl-live.

This documentation is now part of Bio::SeqIO::swiss.pm:



=head2 GN (Gene name) line management details

A Uniprot/Swiss-Prot entry holds information on one protein
sequence. If that sequence is identical across genes and species, they
are all merged into one entry. This creates complex needs for several
annotation fields in swiss-prot format.

The latest syntax for GN line is described in the user manual:

  http://www.expasy.ch/sprot/userman.html#GN_line

Each of the possibly multiple genes in an entry can have Name,
Synonyms (only if there is a name), OrderedLocusNames (names from
genomic sequences) and ORFNames (temporary or cosmid names). "Name"
here really means "symbol". This complexity is now dealth with the
following way:

Each gene is an Bio::Annotation::Collection object that is accessed
like all other annotations. The tag name is 'gene_name':

   my @genes = $seq->annotation->get_Annotations('gene_name');

Note that if you are not interested in the complexity of multiple
genes, you can easily just take the first value:

   my ($gene) = $seq->annotation->get_Annotations('gene_name');

None of the four categories for gene_names are obligatory, so you have
to test returned objects for existence before using them:

   my ($name) = $gene->get_Annotations('name');
   if ($name) {
       print "The official gene symbol is: ". $name->value. "\n";
   }

The can be only one name, so $name is a Bio::Annotation::SimpleValue object.

In other categories (tags: synonyms, orderedlocusnames, orfnames; all
lower case) there can be more than one value, so they are stored in
Bio::Annotation::StructuredValue objects. There can be only one object
with a given tag within a given gene. All values for that category are
stored in an ordered list within the StructureValue object. e.g:

   if ( my ($synonyms) = $gene->get_Annotations('synonyms') ) {
       print "Synonyms: ". join(', ', $synonyms->get_all_values). "\n";
   }

Since Uniprot/Swiss-Prot format have been around for quite some time, the
parser is also able to read in the older GN line syntax where genes
are separated by AND and various symbols by OR. The first symbol is
taken to be the name and the remaining ones are stored as synonyms.


Thanks for Chris Fields for helping out,

Enjoy,

	-Heikki


-- 
______ _/      _/_____________________________________________________
      _/      _/
     _/  _/  _/  Heikki Lehvaslaiho    heikki at_sanbi _ac _za
    _/_/_/_/_/  Senior Scientist    skype: heikki_lehvaslaiho
   _/  _/  _/  SANBI, South African National Bioinformatics Institute
  _/  _/  _/  University of Western Cape, South Africa
     _/      Phone: +27 21 959 2096   FAX: +27 21 959 2512
___ _/_/_/_/_/________________________________________________________