With the ConSite suite of tools assembled, Lenhard et al. [1] conducted several tests to demonstrate the utility of their approach. They analyzed a number of well-characterized human gene promoter regions, comparing sequences with mouse and cow orthologs. They showed that adding the phylogenetic footprinting step improved the selectivity of TFBS prediction by 85% without a great loss of sensitivity. "Phylogenetic footprinting had already been postulated as a means to improve the characterization of the promoter regions of the genes in higher eukaryotic genomes, but the Wasserman article shows that the idea really works," says Guigó. Stormo comments that such programs cannot claim to be fully comprehensive; they will miss some sites, "but the sites that it does identify have a much greater probability of being important. So the reported sites will have a low false-positive rate, in contrast to some of the previous approaches".
The ConSite platform is likely to undergo many modifications and updates as bioinformaticians add new features and capabilities. The ability to align multiple sequences should further improve the phylogenetic footprinting selectivity. "[The authors] don't try to discover new types of sites, just to reliably identify the occurrences of sites for known transcription factors. But the approach can be extended to identifying new sites," says Stormo.
In the future, information from bioinformatic analyses might be combined with experimental datasets to construct models for complex transcriptional regulatory networks. Stormo envisages incorporating data from experiments using microarray analysis, ChIP-on-chip and mutant phenotyping to get a more complete picture of network connections. A recent study from Richard Young and colleagues [10] demonstrated how these approaches can be applied on a genome-wide scale in yeast.
Understanding the genetic networks regulated by transcription-factor activity will not only provide molecular insights into fundamental biological processes: it is also relevant to many disease pathologies and may perhaps indicate novel therapeutic strategies. Computational approaches such as ConSite will prove invaluable in this endeavor. Hunters of the past and present have always begun by tracking down the footprints. Now, genetic hunters have a powerful set of tools to help with their task.