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. 2003 Nov;4(11):1043–1047. doi: 10.1038/sj.embor.7400005

Figure 1.

Figure 1

Human TNF-α pre-mRNA activates PKR through its 2-APRE sensor to enable splicing. The 2-aminopurine response element (2-APRE) in the tumour necrosis factor-α (TNF-α) 3′-untranslated region (UTR; of which the 5′ stem–loop is shown in red) acts as a strong local activator of RNA-dependent protein kinase PKR, allowing messenger RNA splicing to proceed and rendering it highly efficient. When the 2-APRE is prevented from activating PKR, splicing is blocked. Translation yields TNF-α, a secreted inflammatory mediator that can induce expression of more PKR in the cell, creating a positive feedback loop.