HuR and TTP: Two RNA Binding Proteins That Deliver Message From the 3′ End

Differential modulation of COX-2 mRNA translation by HuR and TTP. After transcription of the COX-2 gene, which can be induced by the actions of transcription factors NF-κB, C/EBP and β-catenin/TCF-4, the transcript undergoes capping, splicing and polyadenylation, after which it is transported to the cytoplasm presumably by proteins involved in trafficking. Once in the cytoplasm, the transcript undergoes normal translation and subsequent degradation. ARE sequences in the 3′UTR assume a stem loop structure and interact with ARE-BPs to modulate the stability and translation. In this issue, Young et al demonstrate that in colon cancers HuR levels is increased resulting in increased HuR binding to COX-2 mRNA and consequent increase in stability and translation of COX-2 mRNA. In contrast, expression of TTP reduces in colon cancers, TTP binding would increase mRNA decay, which has been previously shown to occur through exonuclease-mediated deadenylation.