Molecular characterization, expression, and functional analysis of chicken TRAF6

Tumor necrosis factor receptor-associated factor 6 (TRAF6) is a crucial adaptor molecule of the interleukin-1 receptor/Toll-like receptor (IL-1/TLR) superfamily, which can trigger downstream signaling cascades involved in innate immunity. The function of TRAF6 has been clarified in mammals but is poorly understood in chicken. In our study, we investigated TRAF6 function in birds, particularly in chicken innate immune responses, by cloning and characterizing chicken TRAF6 (chTRAF6). The full-length coding sequence of chTRAF6 comprised 1638 bp and encoded a 545-amino acid protein, which shares high sequence similarity with TRAF6 of other species and consists of four structurally conserved domains. Quantitative real-time polymerase chain reaction revealed that chTRAF6 was widely expressed in all tested tissues and its expression was induced in chicken embryo fibroblast cells treated with poly(I:C) and poly(dA:dT). Increased expression of chTRAF6 was observed both in vitro and in vivo following infection with Newcastle disease virus in chickens. Taken together, these results suggest that chTRAF6 plays a vital role in host defense against viral infection in chicken.