Enhanced stability of urokinase-type plasminogen activator mRNA in metastatic breast cancer MDA-MB-231 cells and LLC-PK1 cells down-regulated for protein kinase C--correlation with cytoplasmic heterogeneous nuclear ribonucleoprotein C.
In LLC-PK1 cells, urokinase-type plasminogen activator (uPA) mRNA has a short half-life of 70 min. We have previously demonstrated that most of the regulatory regions responsible for the rapid turnover of uPA mRNA in LLC-PK1 cells reside in its 3' untranslated region (3' UTR), where there are at least three regulatory sites, one of which is A+U-rich. This A+U-rich sequence mediates uPA mRNA stabilization induced by protein kinase C (PKC) down-regulation. In this work, we found that uPA mRNA is rather stable in MDA-MB-231 cells with a half-life of 17 h. We compared the stability of hybrid globin mRNA containing different parts of uPA mRNA in its 3' UTR and found that the A+U-rich sequence of uPA mRNA renders otherwise stable globin mRNA unstable in LLC-PK1 cells but not in MDA-MB-231 cells. We identified a cytoplasmic protein of 40 kDa (p40) which specifically interacts with the A+U-rich sequence. Levels of p40 activity as detected by ultraviolet cross-linking were higher in MDA-MB-231 and PKC-down-regulated LLC-PK1 cells than in untreated LLC-PK1 cells. Prior treatment of the cytoplasm with a specific antibody against heterogeneous nuclear ribonucleoprotein C (hnRNP C) significantly reduced p40 activity. These results suggest a correlation between the A+U-rich sequence-dependent uPA mRNA stabilization in vivo and the binding of hnRNP C to the A+U-rich sequence in vitro.
Nanbu
R
R
Friedrich Miescher Institute, Basel, Switzerland.
Montero
L
L
D'Orazio
D
D
Nagamine
Y
Y
D000818:Animals; D001943:Breast Neoplasms / Q000201:enzymology*; D003593:Cytoplasm / Q000737:chemistry; D015536:Down-Regulation; D005260:Female; D034482:Heterogeneous-Nuclear Ribonucleoprotein Group C; D034441:Heterogeneous-Nuclear Ribonucleoproteins; D006801:Humans; D007668:Kidney / Q000201:enzymology*; D018374:LLC-PK1 Cells; D009362:Neoplasm Metastasis; D010766:Phosphorylation; D011493:Protein Kinase C / Q000502:physiology*; D012333:RNA, Messenger / Q000737:chemistry / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000378:metabolism; D012261:Ribonucleoproteins / Q000032:analysis / Q000502:physiology*; D013552:Swine; D014407:Tumor Cells, Cultured; D014568:Urokinase-Type Plasminogen Activator / Q000235:genetics*
D034482:Heterogeneous-Nuclear Ribonucleoprotein Group C; D034441:Heterogeneous-Nuclear Ribonucleoproteins; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D012261:Ribonucleoproteins; D011493:Protein Kinase C; D014568:Urokinase-Type Plasminogen Activator