Glucocorticoid-induced leucine zipper (GILZ)/NF-κB interaction: role of GILZ homo-dimerization and C-terminal domain

Glucocorticoid-induced leucine zipper (GILZ) is a 137 amino acid protein, rapidly induced by treatment with glucocorticoids (GC), characterized by a leucine zipper (LZ) domain (76–97 amino acids), an N-terminal domain (1–75 amino acids) and a C-terminal PER domain (98–137 amino acids) rich in proline and glutamic acid residues. We have previously shown that GILZ binds to and inhibits NF-κB activity. In the present study we used a number of mutants with the aim of defining the GILZ molecular domains responsible for GILZ/p65NF-κB interaction. Results, obtained by in vitro and in vivo co-immunoprecipitation (Co-IP) and by transcriptional activity experiments, indicate that GILZ homo-dimerization, through the LZ domain, as well as the C-terminal PER domain, particularly the 121–123 amino acids, are both necessary for GILZ interaction with NF-κB, inhibition of transcriptional activity and of IL-2 synthesis.