Acts as a CD40 functional homolog to prevent apoptosis of infected B-lymphocytes and drive their proliferation. Functions as a constitutively active tumor necrosis factor receptor that induces the activation of several signaling pathways, including those of the NF-kappa-B family. LMP1 signaling leads to up-regulation of antiapoptotic proteins and provide growth signals in latently infected cells. Interacts with host UBE2I and subsequently affects the sumoylation state of several cellular proteins. For example, induces the sumoylation of host IRF7 thereby limiting its transcriptional activity and modulating the activation of innate immune responses. Interacts (via PXQXT motif) with host tumor necrosis factor receptor-associated factor (TRAF) proteins TRAF1, TRAF2, TRAF3 and TRAF5. Interacts with human protein ZMYND11; leading to negatively regulate NF-kappa-B activation. Interacts with host UBE2I; this interaction induces the sumoylation of various cellular proteins. Interacts with host IRF7. Two regions, C-terminal-activating region 1 (CTAR1) and CTAR2, have been identified within the cytoplasmic carboxy terminal domain that activates NF-kappa-B. Ubiquitinated on the N-terminus. Belongs to the herpesviridae LMP-1 family.