v-Src oncogene product increases sphingosine kinase 1 expression through mRNA stabilization: alteration of AU-rich element-binding proteins

Oncogene. 2008 Oct 9;27(46):6023-33. doi: 10.1038/onc.2008.198. Epub 2008 Jun 23.

Abstract

Sphingosine kinase 1 (SPHK1) is overexpressed in solid tumors and leukemia. However, the mechanism of SPHK1 overexpression by oncogenes has not been defined. We found that v-Src-transformed NIH3T3 cells showed a high SPHK1 mRNA, SPHK1 protein and SPHK enzyme activity. siRNA of SPHK1 inhibited the growth of v-Src-NIH3T3, suggesting the involvement of SPHK1 in v-Src-induced oncogenesis. v-Src-NIH3T3 showed activations of protein kinase C-alpha, signal transducers and activators of transcription 3 and c-Jun NH(2)-terminal kinase. Their inhibition suppressed SPHK1 expression in v-Src-NIH3T3, whereas their overexpression increased SPHK1 mRNA in NIH3T3. Unexpectedly, the nuclear run-on assay and the promoter analysis using 5'-promoter region of mouse SPHK1 did not show any significant difference between mock- and v-Src-NIH3T3. Furthermore, the half-life of SPHK1 mRNA in mock-NIH3T3 was nearly 15 min, whereas that of v-Src-NIH3T3 was much longer. Examination of two AU-rich region-binding proteins, AUF1 and HuR, that regulate mRNA decay reciprocally, showed decreased total AUF1 protein associated with increased tyrosine-phosphorylated form and increased serine-phosphorylated HuR protein in v-Src-NIH3T3. Modulation of AUF1 and HuR by their overexpression or siRNA revealed that SPHK1 mRNA in v-Src- and mock-NIH3T3 was regulated reciprocally by these factors. Our results showed, for the first time, a novel mechanism of v-Src-induced SPHK1 overexpression.

MeSH terms

  • Animals
  • Antigens, Surface / genetics
  • Antigens, Surface / metabolism
  • Antigens, Surface / physiology
  • Cell Line, Transformed
  • Cell Proliferation / drug effects
  • ELAV Proteins
  • ELAV-Like Protein 1
  • Gene Expression Regulation, Enzymologic
  • Half-Life
  • Heterogeneous Nuclear Ribonucleoprotein D0
  • Heterogeneous-Nuclear Ribonucleoprotein D / genetics
  • Heterogeneous-Nuclear Ribonucleoprotein D / metabolism
  • Heterogeneous-Nuclear Ribonucleoprotein D / physiology
  • Mice
  • Models, Biological
  • NIH 3T3 Cells
  • Oncogene Protein pp60(v-src) / antagonists & inhibitors
  • Oncogene Protein pp60(v-src) / genetics
  • Oncogene Protein pp60(v-src) / physiology*
  • Phosphotransferases (Alcohol Group Acceptor) / genetics*
  • Phosphotransferases (Alcohol Group Acceptor) / metabolism
  • RNA Stability / genetics
  • RNA Stability / physiology*
  • RNA, Messenger / metabolism
  • RNA, Small Interfering / pharmacology
  • RNA-Binding Proteins / genetics
  • RNA-Binding Proteins / metabolism
  • RNA-Binding Proteins / physiology*
  • Regulatory Sequences, Ribonucleic Acid / physiology
  • Signal Transduction / genetics
  • Signal Transduction / physiology
  • Transfection

Substances

  • Antigens, Surface
  • ELAV Proteins
  • ELAV-Like Protein 1
  • ELAVL1 protein, human
  • HNRNPD protein, human
  • Heterogeneous Nuclear Ribonucleoprotein D0
  • Heterogeneous-Nuclear Ribonucleoprotein D
  • Hnrpd protein, mouse
  • RNA, Messenger
  • RNA, Small Interfering
  • RNA-Binding Proteins
  • Regulatory Sequences, Ribonucleic Acid
  • Phosphotransferases (Alcohol Group Acceptor)
  • sphingosine kinase
  • Oncogene Protein pp60(v-src)