HTLV-1 Tax binds to DNA-PKcs. The fusion proteins S-Tax and S-GFP were isolated from 293T cells as described and analyzed for co-precipitation with DNA-PKcs. Shown is the pre-isolated total cell extract (input) for S-GFP (lane 1) and S-Tax (lane 3). Also shown is the affinity purified protein complexes for S-GFP (lane 2) and S-Tax (lane 4). Experimental normalization was achieved by using equal amounts of purified protein.