Tristetraprolin specifically binds to intron regions and regulates alternative splicing of immune response genes in HeLa cells

Tristetraprolin (TTP) regulates inflammatory and immune responses by destabilizing target mRNAs via binding to their 3'-UTR AREs. However, we first found that TTP can regulate gene expression and alternative splicing of inflammatory and immune responses genes in the absence of stimulation. In order to find the regulatory mechanisms, we performed iRIP-seq experiments in HeLa cells. iRIP-seq study revealed that TTP binding sites are enriched in the CDS and intronic RNA regions. We also found that the TTP-targets genes were enriched in positive regulation of I-kappaB kinase/NF-kappaB cascade and positive regulation of NF-kappaB transcription factor activity pathway, such as STAT4, EGR3, RELB, TRIM22, RNF25, and TRAF1. Furthermore, we found that alternative splicing of the innate immune response genes were globally regulated by TTP in HeLa cells. Genome-wide mapping of TTP-RNA interactions now reveal that dominant TTP binding near a competing constitutive splice site, whereas prevalent binding close to an alternative site often causes intron retention. This positional effect was further demonstrated by disrupting a TTP-binding site on minigene constructs and detecting their AS events. These findings suggest a mechanism for TTP to modulate splice site competition to produce opposite functional consequences in HeLa cells. Overall design: RIP-seq analysis of TTP IP versus input in Hela cells