TRAF-3 mRNA splice-deletion variants encode isoforms that induce NF-kappaB activation.
Although TRAF-3 gene products are required for signaling in T-B cell collaboration, full-length TRAF-3 appears to lack signaling function in transient transfection assays that measure NF-kappaB activation. However, the TRAF-3 gene also encodes at least three mRNA splice-deletion variants that predict protein isoforms (delta25aa, delta52aa and delta56aa) with altered zinc (Zn) finger domains and unknown functional capacities. To determine whether TRAF-3 splice-deletion variants may transmit activating receptor signals to the nucleus, cDNAs for five additional splice-variant isoforms (delta27aa, delta83aa, delta103aa, delta130aa and delta221aa) were cloned from a TRAF-3+ lymphoma and the expression and function of each of the eight TRAF-3 splice-deletion variants was analyzed. Among the splice-deletion variants, TRAF-3 delta130 mRNA is expressed by tonsillar B cells and by each of a panel of B and T cell lines. TRAF-3 delta221 protein is expressed by tonsillar B cells and by each of the lymphocytic lines. The functional effect of over-expressing each TRAF-3 splice-deletion variant on NF-kappaB activation was studied in 293 T cells. Seven of the TRAF-3 splice-deletion variants, such as TRAF-3 delta130, induce substantial NF-kappaB-driven luciferase activity (80-500 fold). In contrast, TRAF-3 delta221 (in which the complete Zn finger domain is absent) fails to induce NF-kappaB activation. Although full-length TRAF-3 alone is inactive, it augments the functional effects of the seven activating TRAF-3 splice-deletion variants (1.4-5 fold). These data indicate that alterations of the Zn finger domains render the TRAF-3 splice-deletion variants capable of inducing NF-kappaB activation and that full-length TRAF-3 augments their signaling.
van Eyndhoven
W G
WG
Laboratory of Molecular Immunology, Columbia University, New York, NY 10032, USA.
Gamper
C J
CJ
Cho
E
E
Mackus
W J
WJ
Lederman
S
S
D017398:Alternative Splicing; D002461:Cell Line, Transformed; D002478:Cells, Cultured; D017353:Gene Deletion; D015870:Gene Expression; D014644:Genetic Variation; D006801:Humans; D008214:Lymphocytes; D016328:NF-kappa B / Q000378:metabolism*; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger; D048008:TNF Receptor-Associated Factor 3
D016328:NF-kappa B; D020033:Protein Isoforms; D011506:Proteins; D012333:RNA, Messenger; D048008:TNF Receptor-Associated Factor 3