The NF-kB/Rel family of transcription factors is comprised of several structurally-related proteins that form homodimers and heterodimers and include p50/p105, p52/p100, RelA (p65), and c-Rel/NF-kB. Acting as dimers, these transcription factors bind to kB sites on DNA, thereby regulating expression of target genes. The most common Rel/NF-kB dimer in mammals contains p50-RelA (p50/p65) heterodimers and is an attractive target for potential therapeutics in human inflammation and certain other diseases. Cayman's NF-kB (human p50/p65) Combo Transcription Factor Assay is a non-radioactive, sensitive method for detecting p50 and p65 transcription factor DNA binding activity in nuclear extracts.