The RNA-binding zinc-finger protein tristetraprolin regulates AU-rich mRNAs involved in breast cancer-related processes

Abstract

Tristetraprolin (TTP or ZFP36) is a tandem CCCH zinc finger RNA binding protein that regulates the stability of certain AU-rich mRNAs. Recent work suggests that TTP is deficient in cancer cells when compared to normal cell types. Here we found that TTP expression was lower in invasive breast cancer cells (MDA-MB-231) compared to normal breast cell lines, MCF12A and MCF-10. TTP targets were probed using a novel approach by expressing the C124R zinc finger TTP mutant that act as dominant negative and increase target mRNA expression. In contrast to wt TTP, C124R TTP was able to increase certain ARE-mRNA expression in serum-stimulated breast cancer cells. Using an ARE-gene microarray, novel targets of TTP regulation were identified; urokinase plasminogen activator (uPA), uPA receptor, and matrix metallo-proteinase-1 (MMP1), all known to play prominent roles in breast cancer invasion and metastasis. Expression of these targets was upregulated in the tumorigenic types, particularly, the highly invasive MDA-MB-231. The mRNA half lives of these TTP-regulated genes were increased in TTP-knockout embryonic mouse fibroblasts as assessed by real time PCR while forced restoration of TTP by transfection led to a reduction of their mRNA levels. RNA immunoprecipitation confirmed an association of TTP, but not C124R, with these target transcripts. Moreover, TTP reduced, while the mutant C124R TTP increased, the activity of reporter constructs fused to target ARE. As a result of TTP regulation, invasiveness of MDAMB231 cells was reduced. The data suggest that TTP, in a 3′UTR- and ARE-dependent manner, regulates an important subset of cancer-related genes that are involved in cellular growth, invasion, and metastasis.

The role of the 3' untranslated region in post-transcriptional regulation of protein expression in mammalian cells.

“…45,46 Decreased TTP expression has been suggested to contribute to cancer processes and TTP regulation of important cancer-related transcripts contributes to the suppression of invasive potential of breast cancer cells. 47,48 Furthermore, competition between TTP and HuR in binding to HuR mRNA may influence HuR overexpression and in turn an increased cytoplasmic localization within several cancers. 49 AU-binding factor 1 (AUF1; formerly known as hnRNP D) is a family of four isoforms produced by alternative splicing of a single pre-mRNA (p37, p40, p42 and p45).…”

PARP-14 combines with tristetraprolin in the selective posttranscriptional control of macrophage tissue factor expression

“…30 Macrophage lysates were incubated with protein-G agarose beads precoated with either rabbit anti-TTP, rabbit anti-PARP-14 or normal rabbit IgG. The beads were then washed and incubated in ribonuclease-free DNase I to remove genomic DNA contamination.…”

Tristetraprolin Inhibits the Growth of Human Glioma Cells through Downregulation of Urokinase Plasminogen Activator/Urokinase Plasminogen Activator Receptor mRNAs

“…uPA and uPAR are highly expressed in human glioblastoma tissue samples compared with low-grade or normal brain tissue samples (Gladson et al, 1995). Moreover, TTP has been shown to regulate uPA and uPAR expression in invasive breast cancer cells (Al-Souhibani et al, 2010). In the present study, transient overexpression of TTP in U87MG glioma cells was achieved using Ad-GFP virus (Fig.…”

“…Genes that contain AREs in their 3′UTR include growth factors and protooncogenes (c-fos, c-myc, and VEGF) (Bakheet et al, 2001) as well as invasion-associated genes (uPA,uPAR, (Al-Souhibani et al, 2010). Recent studies have been shown TTP controls the decay of growth factors and proto-oncogenes (Marderosian et al, 2006).…”