Autoregulation of IκBα activity

Transcription factor NF-κB regulates the expression of a plethora of genes. The activity of NF-κB proteins is regulated by IκB proteins. We report that induction of IκBα, a member of the IκB family of proteins, is preceded by activation of NF-κB complex. The promoter of the IκBα gene contains a κB site that is directly involved in its induction by the NF-κB complex. Degradation of IκBα protein precedes activation of NF-κB DNA binding activity, whereas newly synthesized IκBα protein inhibits NF-κB activity. If the degradation of IκBα is prevented, the induction of DNA binding activity of NF-κB complex is severely curtailed. These data suggest the existence of an autoregulatory loop whereby IκBα regulates the activity of transcription factor NF-κB, which in turn regulates the IκBα activity.