v-Src oncogene product increases sphingosine kinase 1 expression through mRNA stabilization: alteration of AU-rich element-binding proteins.
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.
Department of Medical Technology, Nagoya University Graduate School of Health Sciences, Nagoya, Japan.
S
S
Sobue
M
M
Murakami
Y
Y
Banno
H
H
Ito
A
A
Kimura
S
S
Gao
A
A
Furuhata
A
A
Takagi
T
T
Kojima
M
M
Suzuki
Y
Y
Nozawa
T
T
Murate
D000818:Animals; D000954:Antigens, Surface / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D002461:Cell Line, Transformed; D049109:Cell Proliferation / Q000187:drug effects; D051959:ELAV Proteins; D000067780:ELAV-Like Protein 1; D015971:Gene Expression Regulation, Enzymologic; D006207:Half-Life; D000081035:Heterogeneous Nuclear Ribonucleoprotein D0; D034502:Heterogeneous-Nuclear Ribonucleoprotein D / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D051379:Mice; D008954:Models, Biological; D041681:NIH 3T3 Cells; D015688:Oncogene Protein pp60(v-src) / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000235:genetics* / Q000378:metabolism; D020871:RNA Stability / Q000235:genetics / Q000502:physiology*; D012333:RNA, Messenger / Q000378:metabolism; D034741:RNA, Small Interfering / Q000494:pharmacology; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D038621:Regulatory Sequences, Ribonucleic Acid / Q000502:physiology; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology; D014162:Transfection; D000099157:Sphingosine Kinase
D000954:Antigens, Surface; D051959:ELAV Proteins; D000067780:ELAV-Like Protein 1; D000081035:Heterogeneous Nuclear Ribonucleoprotein D0; D034502:Heterogeneous-Nuclear Ribonucleoprotein D; D015688:Oncogene Protein pp60(v-src); D017853:Phosphotransferases (Alcohol Group Acceptor); D012333:RNA, Messenger; D034741:RNA, Small Interfering; D016601:RNA-Binding Proteins; D038621:Regulatory Sequences, Ribonucleic Acid; D000099157:Sphingosine Kinase; C098770:ELAVL1 protein, human; C000630986:HNRNPD protein, human; C000630987:Hnrpd protein, mouse