I highly recommend you to visit [Pathguide][1]Pathguide to get a sense of how vast is the catalog of Pathway Databases. Looking into the category [Pathway Diagrams][2]Pathway Diagrams or in Transcription Factors / Gene Regulatory Networks should help in your task.
I would start by looking at these DataBases:
- GeneMania
- BioCarta
- WikiPathways
- Reactome
If you are working with a species other than human, perhaps you'll find a more suitable database in PathGuide.
Good luck!
PS: Sorry New user limitations impede me to post more than two links :/ [1]: http://pathguide.org/ [2]: http://pathguide.org/#4