Table 1.

Number of transcription regulators in different organisms

Organism	number of genes	number of transcription regulators
yeast	6682	312 (4.7%)
fly	13525	492 (3.6%)
human	22287	1034 (4.6%)

The number of genes and transcriptional regulators (genes annotated with GO term GO:0030528 "transcription regulator activity" for yeast (Saccharomyces cerevisiae) was taken from SGD http://db.yeastgenome.org/cgi-bin/SGD/search/featureSearch and for fly (Drosophila melanogaster, DROM3) and human (Homo sapiens, NCBI 34 dbSNP120) was taken from ENSEMBL http://www.ensembl.org/Multi/martview