Tristetraprolin recruits functional mRNA decay complexes to ARE sequences

Son

et al. 2009

Intl Journal of Cancer

Tristetraprolin (TTP) is an AU‐rich element‐binding protein that regulates mRNA stability. Here, we report that TTP suppress the growth of human colon cancer cells both in vivo and in vitro by regulating of the expression of vascular endothelial growth factor (VEGF). TTP protein expression in human colonic tissues was markedly decreased in colonic adenocarcinoma compared with in normal mucosa and adenoma. VEGF expression was higher in colonic adenocarcinoma than in normal mucosa and adenoma. Specific inhibition of TTP expression by RNA‐interference increased the expression of VEGF in cultured human colon cancer cells, and TTP overexpression markedly decreased it. In addition, elevated expression of TTP decreased the expression level of luciferase linked to a 3′ terminal AU‐rich element (ARE) of VEGF mRNA. Colo320/TTP cells overexpressing TTP grew slowly in vitro and became tumors small in size when xenografted s.c into nude mice. These findings demonstrate that TTP acts as a negative regulator of VEGF gene expression in colon cancer cells, suggesting that it can be used as novel therapeutic agent to treat colon cancer.

Section: Ttp Inhibits Growth Of Colon Cancer Cells In Vitromentioning

confidence: 99%

Tristetraprolin regulates expression of VEGF and tumorigenesis in human colon cancer

Son

et al. 2009

Intl Journal of Cancer

Expert Review of Proteomics

“…TTP binds to AU-rich elements (AREs) with high affinity for UUAUUUAUU nucleotides within mRNA sequences [2][3][4][5][6][7]. The specific binding of TTP to AREs causes destabilization of mRNA molecules encoding proteins such as tumor necrosis factor-alpha (TNFα) [3,[8][9][10], granulocyte-macrophage colony-stimulating factor (GM-CSF) [11,12], cyclooxygenase 2 (COX2) [13,14], interleukin 2 (IL2) [15] and transcription factor E47 [16].…”

Section: Introductionmentioning

confidence: 99%

Phosphorylation site analysis of the anti-inflammatory and mRNA-destabilizing protein tristetraprolin

Cao¹,

Deterding²,

Blackshear³

2007

Tristetraprolin (TTP) is a member of the CCCH zinc finger proteins and is an anti-inflammatory protein. Mice deficient in TTP develop a profound inflammatory syndrome with erosive arthritis, autoimmunity and myeloid hyperplasia. TTP binds to mRNA AU-rich elements with high affinity for UUAUUUAUU nucleotides and causes destabilization of those mRNA molecules. TTP is phosphorylated extensively in vivo and is a substrate for multiple protein kinases in vitro. A number of approaches have been used to identify its phosphorylation sites. This article highlights the recent progress and different approaches utilized for the identification of phosphorylation sites in mammalian TTP. Important but limited results are obtained using traditional methods including in vivo labeling, site-directed mutagenesis, phosphopeptide mapping and protein sequencing. Mass spectrometry including MALDI/MS, MALDI/MS/MS, LC/MS/MS, IMAC/MALDI/MS/MS and multidimensional protein identification technology (MudPIT) has led the way in identifying TTP phosphorylation sites. The combination of these approaches has identified multiple phosphorylation sites in mammalian TTP, some of which are predicted by motif scanning to be phosphorylated by several protein kinases. This information should provide the molecular basis for future investigation of TTP's regulatory functions in controlling pro-inflammatory cytokines.

Journal of Biological Chemistry

“…24). The identification of mRNA decay factors that associate with TTP and different mRNA decay assays suggests that TTP promotes mRNA turnover by recruiting the mRNA decay enzymes responsible for deadenylation, decapping, and 5Ј to 3Ј turnover, as well as 3Ј to 5Ј exonucleolytic degradation (25)(26)(27)(28)(29)(30). An unresolved issue is the diversity of interactions that allow mRNA specific-binding proteins to recruit the mRNA degradation machinery.…”

mentioning

confidence: 99%

The Cth2 ARE-binding Protein Recruits the Dhh1 Helicase to Promote the Decay of Succinate Dehydrogenase SDH4 mRNA in Response to Iron Deficiency

Pedro-Segura

Vergara

Rodrı́guez-Navarro

et al. 2008

107

Iron is an essential nutrient that participates as a redox cofactor in a broad range of cellular processes. In response to iron deficiency, the budding yeast Saccharomyces cerevisiae induces the expression of the Cth1 and Cth2 mRNA-binding proteins to promote a genome-wide remodeling of cellular metabolism that contributes to the optimal utilization of iron. Cth1 and Cth2 proteins bind to specific AU-rich elements within the 3-untranslated region of many mRNAs encoding proteins involved in iron-dependent pathways, thereby promoting their degradation. Here, we show that the DEAD box Dhh1 helicase plays a crucial role in the mechanism of Cth2-mediated mRNA turnover. Yeast two-hybrid experiments indicate that Cth2 protein interacts in vivo with the carboxyl-terminal domain of Dhh1. We demonstrate that the degradation of succinate dehydrogenase SDH4 mRNA, a known target of Cth2 on iron-deficient conditions, depends on Dhh1. In addition, we localize the Cth2 protein to cytoplasmic processing bodies in strains defective in the 5 to 3 mRNA decay pathway. Finally, the degradation of trapped SDH4 mRNA intermediates by Cth2 supports the 5 to 3 directionality of mRNA turnover. Taken together, these results suggest that Cth2 protein recruits the Dhh1 helicase to ARE-containing mRNAs to promote mRNA decay.