<p>Oligonucleotides used in this study.</p>

This maintains elevated levels of total and phosphorylated p65 (p-p65), facilitating p65 nuclear translocation and enhancing its transcriptional activity. EseJ also interacts with TAK1 and TRAF6 (both are upstream of the NF-κB signaling pathway) via its central domain (aa 243–532), thereby promoting the formation of a stable TRAF6-TAK1 complex. This interaction increases the TRAF6-dependent K27-linked polyubiquitination of TAK1, driving TAK1 phosphorylation and the subsequent activation of the IKK-IκB-NF-κB cascade.

Inhibiting TAK1 abrogates this signaling, confirming the essential role of TAK1 in EseJ-induced NF-κB activation. <i>In vivo</i> studies using zebrafish larvae also demonstrated that EseJ is required for <i>E. piscicida</i> to induce the production of pro-inflammatory cytokines. Together, we provide evidence that EseJ targets both TAK1 and p65 to promote NF-κB-dependent inflammatory responses. Given the similarities among EseJ homologues in other bacteria, our finding may reveal a conserved effector-mediated immune signaling across diverse Gram-negative pathogens.</p></div>