The tumor necrosis factor-α AU-rich element inhibits the stable association of the 40S ribosomal subunit with RNA transcripts

Tumor necrosis factor-alpha (TNF-α) is a potent cytokine that is central to normal immune responses as well as autoimmune inflammatory diseases. The production of TNF-α protein is thus tightly regulated at multiple levels. Translational control is one of the means by which TNF-α production is repressed in unstimulated cells. To examine the mechanism by which the translation of TNF-α mRNA transcripts is repressed, we have used an in vitro translation system. The AU-rich element (ARE) in the 3′ UTR of TNF-α transcripts was sufficient to confer translational repression. This effect was observed using transcripts containing a 5′ m7G cap but not uncapped transcripts, and was independent of a poly(A) tail. Sucrose gradient analysis revealed that ARE-containing transcripts were present at relatively lower amounts in 80S-associated fractions and higher amounts in non-ribosome-bound RNA fractions, with no accumulation of 48S-associated transcripts. ARE-mediated translational repression was competitively inhibited by ARE-containing transcripts. These data indicate that a TNF-α ARE-binding trans-acting factor(s) inhibits the association of the 43S complex with RNA transcripts.