use warnings;
use strict;

my $sentence = "Furthermore , expression of <GENE> Vpu </GENE> in Jurkat T cells rendered them more susceptible to <GENE> Fas </GENE> - induced death ";
$sentence =~ s/<GENE>\s*(((?!<GENE>|<\/GENE>).)+)\s*<\/GENE>//gi;
print "$sentence\n";

__END__

Furthermore , expression of  in Jurkat T cells rendered them more susceptible to  - induced death