A Ubiquitin-Proteasome Pathway Represses the Drosophila Immune Deficiency Signaling Cascade

Background: The inducible production of antimicrobial peptides is a major immune response in Drosophila. The genes encoding these peptides are activated by NF-κB transcription factors that are controlled by two independent signaling cascades: the Toll pathway that regulates the NF-κB homologs, Dorsal and DIF; and the IMD pathway that regulates the compound NF-κB-like protein, Relish. Although numerous components of each pathway that are required to induce antimicrobial gene expression have been identified, less is known about the mechanisms that either repress antimicrobial genes in the absence of infection or that downregulate these genes after infection.