Open AccessEnhanced Stability of Urokinase‐Type Plasminogen Activator mRNA in Metastatic Breast Cancer MDA‐MB‐231 Cells and LLC‐PK 1 Cells Down‐Regulated for Protein Kinase C — Correlation with Cytoplasmic Heterogeneous Nuclear Ribonucleoprotein C
Author(s) -
Nanbu Rika,
Montero Lilian,
D'orazio Daniel,
Nagamine Yoshikuni
Publication year - 1997
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1997.00169.x
Subject(s) - messenger rna , microbiology and biotechnology , untranslated region , urokinase receptor , plasminogen activator , protein kinase c , biology , three prime untranslated region , heterogeneous nuclear ribonucleoprotein , kinase , gene , rna , ribonucleoprotein , biochemistry , endocrinology
In LLC‐PK 1 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‐PK 1 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‐PK 1 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‐PK 1 cells than in untreated LLC‐PK, 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.