Activates the JUN N-terminal pathway through activation of the MAP kinase kinase MAP2K7. Acts synergistically with PRDX3 to regulate the activation of NF-kappa-B in the cytosol. This activation is kinase-dependent and involves activating the IKK complex, the IKBKB-containing complex that phosphorylates inhibitors of NF-kappa-B. ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Activated by autophosphorylation and homodimerization. Homodimer; forms dimers through the leucine-zipper motif. Interacts with the C-terminus of MAPK8IP1 through the kinase catalytic domain. Binds PRDX3. Associates with the IKK complex through the kinase domain. Expressed in the adult brain, liver, placenta and pancreas, with expression strongest in the pancreas. Autophosphorylated on serine and threonine residues. May be produced at very low levels due to a premature stop codon in the mRNA, leading to nonsense-mediated mRNA decay. Belongs to the protein kinase superfamily. STE Ser/Thr protein kinase family. MAP kinase kinase kinase subfamily. Wrong choice of CDS. Truncated C-terminus.