Thrombopoietin upregulates nucleolin mRNA and protein in thrombopoietin-dependent megakaryocytic cell line, UT-7/TPO.
Thrombopoietin (TPO) is a hematopoietic cytokine that regulates megakaryocytosis and thrombocytosis by binding to its receptor (c-Mpl). The signaling pathways downstream of c-Mpl include the Ras/Raf/MAP kinase and JAK/STAT pathway and are transduced into the regulation of immediate early-, early- and delayed-response genes. How these genes couple c-Mpl activation to the biochemical machinery of cell growth and cell cycle progression in hematopoietic cells is still unclear. UT-7/TPO is a recently characterized TPO-dependent cell line. Using RNA fingerprinting with arbitrarily primed PCR (RAP-PCR) to identify the TPO-regulated genes in this cell line, we found that the mRNA expression of nucleolin was upregulated in the UT-7/TPO cells in response to TPO. Concomitantly, the TPO-stimulated cells expressed an increased amount of full length nucleolin as determined by immunoblot analysis. The TPO-induced upregulation of nucleolin mRNA was not inhibited by the MEK1/2 inhibitor PD98059, suggesting that ERK/MAPK activation is not necessary for elevation of nucleolin gene expression in response to TPO in UT-7/TPO. Nucleolin is a multifunctional nucleolar protein thought to be involved in many cellular processes, including ribosome biogenesis, the processing of ribosomal RNA (rRNA), mRNA stability, transcriptional regulation, and cell proliferation. Thus, these results indicate that the upregulation of nucleolin mRNA and protein may be important for the TPO-induced effects of hematopoietic cells.
Ito
Takatoshi
T
Japanese Red Cross, Hokkaido Red Cross Blood Center, Sapporo, Japan.
Fujihara
Mitsuhiro
M
Oda
Atsushi
A
Wakamoto
Shinobu
S
Yamaguchi
Miki
M
Komatsu
Norio
N
Miyazaki
Hiroshi
H
Azuma
Hiroshi
H
Ikeda
Hisami
H
Ikebuchi
Kenji
K
D001483:Base Sequence; D002460:Cell Line; D002478:Cells, Cultured; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology; D020869:Gene Expression Profiling / Q000379:methods; D008533:Megakaryocytes / Q000166:cytology* / Q000187:drug effects; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D008969:Molecular Sequence Data; D010750:Phosphoproteins / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism*; D016133:Polymerase Chain Reaction / Q000379:methods; D012333:RNA, Messenger / Q000187:drug effects; D016601:RNA-Binding Proteins / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism*; D017422:Sequence Analysis, DNA; D012689:Sequence Homology, Nucleic Acid; D013926:Thrombopoietin / Q000494:pharmacology*; D015854:Up-Regulation / Q000187:drug effects*; D000097796:Nucleolin
D004791:Enzyme Inhibitors; D005419:Flavonoids; D020928:Mitogen-Activated Protein Kinases; D010750:Phosphoproteins; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D013926:Thrombopoietin; D000097796:Nucleolin; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one