Affinity purification and characterization of CIF, an insect immunoresponsive factor with NF-κ-B-like properties

1. 1. A rapid DNA affinity purification procedure was worked out for the purification of the Cecropia Immunoresponsive Factor (CIF) from the pupae of Hyalophora cecropia. 2. 2. CIF consists of a single polypeptide chain of 65 kDA and is present as a homodimer under native conditions. 3. 3. CIF binds to the κB-like sequences upstream of the H. cecropia immune genes with the following order of affinity: attacin κB > lysozyme κB > cecropin A κB > cecropin B κB. 4. 4. The purified CIF also strongly binds to the κB sequences from both the immunoglobulin kappa light chain gene and the MHC class I gene. 5. 5. The DNA binding of CIF can be inhibited by antisera directed against NF-κB-related proteins. 6. 6. The cytoplasmic factor C1, co-purified from the affinity column, contains two polypeptide chains, one of which has the same molecular weight as CIF.