IκBζ expression is regulated by miR-124a

I kappa B zeta belongs to the nuclear members of the I kappa B protein family. Its function in regulating the activity of the transcription factor NF kappa B is poorly understood. Here, we demonstrate that human I kappa B zeta is posttranscriptionally regulated by microRNA (miR)-124a. In HepG2 cells miR-124a was not endogenously expressed, but upon enforced expression dramatically inhibited the interleukin-1 beta-induced protein expression of I kappa B zeta. The predicted binding site for miR-124a in the 3'UTR of the I kappa B zeta mRNA revealed an imperfect match resulting in miR-124a-mediated suppression of I kappa B zeta expression through translational repression. Reporter gene analyses revealed that miR-124a targets I kappa B zeta mRNA through base pairing to the partially complementary sequence in the 3'UTR that was predicted as a binding site by in silico analysis. Furthermore, we demonstrate that the 7mer seed match is sufficient for recognition of the I kappa B zeta mRNA. Together, our data identify I kappa B zeta as a target of miR-124a that might be involved in the fine-tuning of NF kappa B-mediated gene expression.