Post-transcriptional Regulation of Programmed Cell Death 4 (PDCD4) mRNA by the RNA-binding Proteins Human Antigen R (HuR) and T-cell Intracellular Antigen 1 (TIA1)

• Published in: The Journal of biological chemistry 2015-02, Vol.290 (6), p.3468-3487
• Main Authors: Wigington, Callie P., Jung, Jeenah, Rye, Emily A., Belauret, Sara L., Philpot, Akahne M., Feng, Yue, Santangelo, Philip J., Corbett, Anita H.
• Format: Article
• Language: English
• Subjects: Apoptosis Regulatory Proteins - genetics; Apoptosis Regulatory Proteins - metabolism; Cell Nucleus - metabolism; Cytoplasm - metabolism; ELAV Proteins - genetics; ELAV Proteins - metabolism; Humans; HuR; Imaging; MCF-7 Cells; PDCD4; Poly(A)-Binding Proteins - genetics; Poly(A)-Binding Proteins - metabolism; Post-transcriptional Regulation; Protein Binding; RNA; RNA Processing; RNA Processing, Post-Transcriptional; RNA Stability; RNA, Messenger - genetics; RNA, Messenger - metabolism; RNA-binding Protein; RNA-Binding Proteins - genetics; RNA-Binding Proteins - metabolism; RNA-Protein Interaction; T-Cell Intracellular Antigen-1; TIA1
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M114.631937

Post-transcriptional processing of mRNA transcripts plays a critical role in establishing the gene expression profile of a cell. Such processing events are mediated by a host of factors, including RNA-binding proteins and microRNAs. A number of critical cellular pathways are subject to regulation at multiple levels that allow fine-tuning of key biological responses. Programmed cell death 4 (PDCD4) is a tumor suppressor and an important modulator of mRNA translation that is regulated by a number of mechanisms, most notably as a target of the oncomiR, miR-21. Here, we provide evidence for post-transcriptional regulation of PDCD4 by the RNA-binding proteins, HuR and TIA1. Complementary approaches reveal binding of both HuR and TIA1 to the PDCD4 transcript. Consistent with a model where RNA-binding proteins modulate the PDCD4 transcript, knockdown of HuR and/or TIA1 results in a significant decrease in steady-state PDCD4 mRNA and protein levels. However, fractionation experiments suggest that the mode of regulation of the PDCD4 transcript likely differs in the cytoplasm and the nucleus as the pool of PDCD4 mRNA present in the cytoplasm is more stable than the nuclear pool of PDCD4 transcript. We observe a competitive mode of binding between HuR and TIA1 on the PDCD4 transcript in the cytoplasm, suggesting that these two factors dynamically interact with one another as well as the PDCD4 transcript to maintain tight control of PDCD4 levels. Overall, this study reveals an additional set of regulatory interactions that modulate the expression of PDCD4, a key pro-apoptotic factor, and also reveals new insights into how HuR and TIA1 functions are integrated to achieve such regulation. Background: PDCD4 is regulated by multiple mechanisms and is involved in tumor promotion. Results:PDCD4 mRNA is bound by the RNA-binding proteins HuR and TIA1, resulting in modulation of PDCD4 mRNA and protein levels. Conclusion: This study describes a dynamic regulation of PDCD4 mRNA via the 3′UTR. Significance: This work reveals an additional regulatory mechanism that modulates levels of the tumor suppressor PDCD4.