Transcriptional regulatory network topology from statistics of DNA binding sites

We show that the out-degree distribution of the gene regulation network of the budding yeast, Saccharomyces cerevisiae, can be reproduced to high accuracy from the statistics of TF binding sequences. Our observation suggests a particular microscopic mechanism for the observed universal global topology in these networks. The numerical data and analytical solution of our model disagree with a simple power-law for the experimentally obtained degree distribution in the case of yeast.