An IL-1 family cytokine binds to an IL-1 receptor (IL-1R). The signal is transmitted via the TIR adaptor MyD88 which causes IL-1R associated kinases (IRAKs) to migrate towards the receptor. When activated, IRAKs prompt the protein TNFR-associated factor 6 (TRAF6) to be polyubiquitinated, that is, to cause many ubiquitins to bind to it. Polyubiquitinated TRAF6 interacts with the TAK1 unit of a TAK1-TAB1-TAB2 complex which causes the IκBα unit of NF-κB to become phosphorylated and dissociate from the rest of the subunits. The phosphorylated IκBα is eventually degraded, but the remaining two subunits of NF-κB can be phosphorylated and act as a transcription factor for pro-inflammatory genes. Besides prompting NF-κB dependent gene expression, the TAK1-TAB1-TAB2 complex can activate mitogen-activated protein kinases (MAPKs), JNK and p38 by phosphorylating them. Activated JNK and p38 can go on to activate transcription factors such as AP1, CHP, and ATF2 which can also promote the transcription of pro-inflammatory genes.