2-AMINOPURINE SELECTIVELY INHIBITS SPLICING OF TUMOR-NECROSIS-FACTOR-ALPHA MESSENGER-RNA

2-Aminopurine (2-AP) inhibits specific kinases that phosphorylate the a subunit of eukaryotic translation initiation factor 2. One of these, PKR, is also involved in signal transduction. We show here that 2-AP selectively inhibits expression of tumor necrosis factor alpha (TNF-al pha) mRNA in primary human lymphoid cells. 2-AP does not inhibit trans cription of the human TNF-alpha gene, nor does it affect mRNA stabilit y. Instead, the flow of short-lived precursor transcripts into mature TNF-alpha mRNA is blocked. When 2-AP is present during induction, unsp liced TNF-alpha precursor transcripts accumulate at the expense of mRN A. Using RNase protection analysis with genomic probes for different e xon-intron junctions, we show that 2-AP blocks splicing of TNF-alpha m RNA. Neither the TNF-beta nor the interleukin-1 beta gene shows such r egulation. 2-AP also inhibits splicing of precursor RNA transcribed fr om an exogenous human TNF-alpha gene. Sequences within this gene thus confer sensitivity to 2-AP. Yet, control is not exerted at a specific splice site. Our results reveal the involvement of a 2-AP-sensitive co mponent, expressed in functional form before induction, in the splicin g of TNF-alpha mRNA.