Dual role of the ddx5/ddx17 RNA helicases in the control of the pro-migratory NFAT5 transcription factor

Abstract

Ddx5 and ddx17 are two highly related RNA helicases involved in both transcription and splicing. These proteins coactivate transcription factors involved in cancer such as the estrogen receptor alpha, p53 and beta-catenin. Ddx5 and ddx17 are part of the splicing machinery and can modulate alternative splicing, the main mechanism increasing the proteome diversity. Alternative splicing also has a role in gene expression level regulation when it is coupled to the nonsensemediated mRNA decay (NMD) pathway. In this work, we report that ddx5 and ddx17 have a dual role in the control of the pro-migratory NFAT5 transcription factor. First, ddx5 and ddx17 act as transcriptional coactivators of NFAT5 and are required for activating NFAT5 target genes involved in tumor cell migration. Second, at the splicing level, ddx5 and ddx17 increase the inclusion of NFAT5 exon 5. As exon 5 contains a pre-mature translation termination codon, its inclusion leads to the regulation of NFAT5 mRNAs by the NMD pathway and to a decrease in NFAT5 protein level. Therefore, we demonstrated for the first time that a transcriptional coregulator can simultaneously regulate the transcriptional activity and alternative splicing of a transcription factor. This dual regulation, where ddx5 and ddx17 enhance the transcriptional activity of NFAT5 although reducing its protein expression level, suggests a critical role for ddx5 and ddx17 in tumor cell migration through the fine regulation of NFAT5 pathway.

Systematic Determination of Human Cyclin Dependent Kinase (CDK)-9 Interactome Identifies Novel Functions in RNA Splicing Mediated by the DEAD Box (DDX)-5/17 RNA Helicases*

“…DDX5 and DDX17 mediated regulation of mH2A1 alternatively spliced isoforms influences expression of mH2A1-dependent downstream genes involved in redox metabolism (38). We therefore measured the effect of DDX5/17 depletion on the expression profiles of hydroxyacid oxidase 1 (HAO1), Rieske (Fe-S) domain containing (RFESD), and extracellular superoxide dismutase 3 (SOD3).…”

“…It has been shown that DDX5 and DDX17 regulate the alternative splicing of the promigratory transcription factor nuclear factor of activated T-cells 5 (NFAT5) and the histone macroH2A1 (38). The human NFAT5 gene has known alternatively included exons 4 and 5.…”

Inhibitory phosphorylation of GSK-3β by AKT, PKA, and PI3K contributes to high NaCl-induced activation of the transcription factor NFAT5 (TonEBP/OREBP)

“…(16), and p38␣ (35, 73), and phosphatases, including SHP-1 (74), contribute to signaling high NaCl-induced activation of NFAT5. In addition to its role in activating expression of osmoprotective genes, NFAT5 is also involved in biological processes that apparently do not involve hypertonic stress, including cardiac development and function (42), vascular smooth muscle migration (26), skeletal muscle myogenesis (47), cancer progression and metastasis (7,22), replication of HIV-1, HIV-2, and multiple simian immunodeficiency (53, 54), SFFVp virus replication (67), and expression of multiple Toll-like receptor-induced genes (5).Glycogen synthase kinase-3␤, GSK-3␤ (GSK3B), is a ubiquitously expressed serine/threonine kinase that was originally characterized as phosphorylating and inactivating glycogen synthase, the rate-limiting enzyme of glycogen synthesis (28). Since then, GSK-3␤ has been found to regulate a wide variety of biological processes such as function of neurons (29), immunological responses (63), cardiac hypertrophy (8), and cancer (43).…”

“…(16), and p38␣ (35, 73), and phosphatases, including SHP-1 (74), contribute to signaling high NaCl-induced activation of NFAT5. In addition to its role in activating expression of osmoprotective genes, NFAT5 is also involved in biological processes that apparently do not involve hypertonic stress, including cardiac development and function (42), vascular smooth muscle migration (26), skeletal muscle myogenesis (47), cancer progression and metastasis (7,22), replication of HIV-1, HIV-2, and multiple simian immunodeficiency (53, 54), SFFVp virus replication (67), and expression of multiple Toll-like receptor-induced genes (5).…”

Lipocalin 2 (LCN2), the TNF-like receptor TWEAKR and its ligand TWEAK act downstream of NFAT1 to regulate breast cancer cell invasion.

“…Because of their role in critical signalling pathways that control cell fate (Baksh et al, 2002;Chuvpilo et al, 2002;Xanthoudakis et al, 1996), one would expect that disturbing NFAT signalling could impact carcinogenesis. Indeed, beside their role in the migratory and invasive capacities of breast cancer cells (Fougère et al, 2010;Jauliac et al, 2002;Yiu and Toker, 2006;Yoeli-Lerner et al, 2005;Germann et al, 2012), there is growing evidence for an active role of NFAT factors in carcinogenesis (Buchholz et al, 2006;Dejmek et al, 2006;Foldynová-Trantírková et al, 2010;Holzmann et al, 2004;Jönsson et al, 2002). However, beside these reports of a ''pro-cancer'' role, others are showing the ''anti-cancer'' capacities of NFAT factors (Glud et al, 2005;Lee et al, 2005;Wu et al, 2010).…”