The seventh ring: exploring TRAF7 functions.

Tumor necrosis factor receptor-associated factors (TRAFs) have been discovered and characterized by their capacity to link tumor necrosis factor receptors (TNFR) family proteins to signaling pathways that transduce the cellular effects mediated by TNF family ligands. There are seven known mammalian TRAF proteins (TRAF1-7), that share a domain organization made of a modular structure, characteristic of adaptor proteins whose function is to link structurally dissimilar factors. Functionally, TRAF proteins mediate the assembly of cytoplasmic signal transducers and regulatory molecules downstream of receptors complexes. Despite the similarities in the signaling pathways activated by the different TRAF proteins, each appears to play distinct physiological roles. TRAF7 is the last member of the TRAF family that has been identified. Yet, the functional characterization of TRAF7 presents some aspects still obscure and poorly defined, making this protein arguably the most mysterious member of the family. In fact, recent data indicate that TRAF7 is involved in signal transduction pathways that lead either to activation or repression of NF-κB transcription factor. In addition, TRAF7 regulates activation of cellular stress pathways, as well as unconventional ubiquitination events and differentiation of muscle tissue. In this review, we try to summarize the most recent advances in our understanding of TRAF7 function and the biological processes of this protein is involved in.