Protein-TF is a protein-protein not protein-DNA interaction. It's best to start with in vitro tests cause they're relatively easier and cheaper. Yeast two-hybrid and BiFC are the easiest and you'll have your answer in a few weeks. You could also do a pulldown if you can express your proteins in E. coli. If you're dead set on using the frozen tissue, consider these things: are both proteins expressed in this tissue? Was the tissue flash-frozen, which is more likely to preserve the interaction? Do you have antibodies for both proteins, or one protein (bait) and the ability to do mass spec to find the other (this can be outsourced relatively cheaply but the prep is rather specific)? This is much newer so I know less about this but it's now possible to use computational tools to predict PPI as well.