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The enzyme 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatases 3 (PFKFB3) catalyzes the first committed rate-limiting step of glycolysis and is upregulated in cancer cells. The mechanism of PFKFB3 expression upregulation in cancer cells has not been fully elucidated. The PFKFB3 3'-UTR is reported to contain AU-rich elements (AREs) that are important for regulating PFKFB3 mRNA stability. However, the mechanisms by which PFKFB3 mRNA stability is determined by its 3'-UTR are not well known. We demonstrated that tristetraprolin (TTP), an ARE-binding protein, has a critical function regulating PFKFB3 mRNA stability. Our results showed that PFKFB3 mRNA contains three AREs in the 3'-UTR. TTP bound to the 3rd ARE and enhanced the decay of PFKFB3 mRNA. Overexpression of TTP decreased PFKFB3 expression and ATP levels but increased GSH level in cancer cells. Overexpression of PFKFB3 cDNA without the 3'-UTR rescued ATP level and GSH level in TTP-overexpressing cells. Our results suggested that TTP post-transcriptionally downregulated PFKFB3 expression and that overexpression of TTP may contribute to suppression of glycolysis and energy production of cancer cells in part by downregulating PFKFB3 expression., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Mitochondrial dynamics, including constant fusion and fission, play critical roles in maintaining mitochondrial morphology and function. Here, we report that developmentally regulated GTP-binding protein 2 (DRG2) regulates mitochondrial morphology by modulating the expression of the mitochondrial fission gene dynamin-related protein 1 (Drp1). shRNA-mediated silencing of DRG2 induced mitochondrial swelling, whereas expression of an shRNA-resistant version of DRG2 decreased mitochondrial swelling in DRG2-depleted cells. Analysis of the expression levels of genes involved in mitochondrial fusion and fission revealed that DRG2 depletion significantly decreased the level of Drp1. Overexpression of Drp1 rescued the defect in mitochondrial morphology induced by DRG2 depletion. DRG2 depletion reduced the mitochondrial membrane potential, oxygen consumption rate (OCR), and amount of mitochondrial DNA (mtDNA), whereas it increased reactive oxygen species (ROS) production and apoptosis. Taken together, our data demonstrate that DRG2 acts as a regulator of mitochondrial fission by controlling the expression of Drp1., (Copyright © 2017 Elsevier Inc. All rights reserved.)

cIAP2 is a key regulator of programmed cell death and the NF-κB pathway. Here, we investigated the post-transcriptional regulation of cIAP2 expression by tristetraprolin (TTP). Our results showed that overexpression of TTP reduced the stability of cIAP2 mRNA and the expression level of cIAP2. In addition, TTP destabilized a luciferase mRNA containing cIAP2 mRNA 3'UTR. cIAP2 mRNA 3'UTR contains four AU-rich elements (AREs) and the 2nd ARE was responsible for the TTP-mediated destabilization of the cIAP2 mRNA. RNA EMSA revealed that TTP directly bound to 42 nucleotides from the 3'UTR of cIAP2 mRNA containing the 2nd ARE. However, the 42 nucleotides did not promote TTP-dependent destabilization of mRNA and did not recruit the decapping enzyme Dcp2 and the 5'-3' exonuclease Xrn1. When we used a 52 nucleotide sequence containing an additional 5 nucleotides from cIAP2 mRNA 3'UTR at both ends, this long nucleotide sequences recruited Dcp2 and Xrn1 and promoted TTP-dependent destabilization of mRNA. Collectively, our results suggest that TTP can bind to the 2nd ARE of cIAP2 mRNA 3'UTR and destabilize cIAP2 mRNA by forming complexes with Dcp2 and Xrn1. However, while a short nucleotide sequence containing the 2nd ARE of cIAP2 mRNA can recruit the TTP binding, this cannot recruit Dcp2 and Xrn1 and cannot induce TTP-mediated destabilize the mRNA. Instead, additional nucleotide sequences are required to recruit Dcp2 and Xrn1 and to destabilize mRNA., (Copyright © 2010 Elsevier Inc. All rights reserved.)