Tumor protein D52 expression is post-transcriptionally regulated by T-cell intercellular antigen (TIA) 1 and TIA-related protein via mRNA stability

Abstract

Although tumor protein D52 (TPD52) family proteins were first identified nearly 20 years ago, their molecular regulatory mechanisms remain unclear. Therefore, we investigated the post-transcriptional regulation of TPD52 family genes. An RNA immunoprecipitation (RIP) assay showed the potential binding ability of TPD52 family mRNAs to several RNA-binding proteins, and an RNA degradation assay revealed that TPD52 is subject to more prominent post-transcriptional regulation than are TPD53 and TPD54. We subsequently focused on the 3′-untranslated region (3′-UTR) of TPD52 as a cis-acting element in post-transcriptional gene regulation. Several deletion mutants of the 3′-UTR of TPD52 mRNA were constructed and ligated to the 3′-end of a reporter green fluorescence protein gene. An RNA degradation assay revealed that a minimal cis-acting region, located in the 78-280 region of the 5′-proximal region of the 3′-UTR, stabilized the reporter mRNA. Biotin pull-down and RIP assays revealed specific binding of the region to T-cell intracellular antigen 1 (TIA-1) and TIA-1-related protein (TIAR). Knockdown of TIA-1/TIAR decreased not only the expression, but also the stability of TPD52 mRNA; it also decreased the expression and stability of the reporter gene ligated to the 3′-end of the 78-280 fragment. Stimulation of transforming growth factor-β and epidermal growth factor decreased the binding ability of these factors, resulting in decreased mRNA stability. These results indicate that the 78-280 fragment and TIA-1/TIAR concordantly contribute to mRNA stability as a cis-acting element and trans-acting factor(s), respectively. Thus, we here report the specific interactions between these elements in the post-transcriptional regulation of the TPD52 gene.