How transcription factors (TFs), the ultimate targets and executors of cellular signalling pathways, are regulated via protein-protein interactions remains elusive. To systematically investigate the regulations and functions of human transcription factors, we performed proteomics studies of soluble and chromatin-associated complexes of 56 TFs in HEK293T cells, using tandem-affinity-purification followed by mass spectrometry (TAP/MS). We performed 214 purifications and identified 2,156 high-confident protein-protein interactions.