scholarly journals Epidermal growth factor increases the level of the cyclin-dependent kinase (CDK) inhibitor p21/CIP1 (CDK-interacting protein 1) in A431 cells by increasing the half-lives of the p21/CIP1 transcript and the p21/CIP1 protein

1999 ◽  
Vol 337 (3) ◽  
pp. 599 ◽  
Author(s):  
Lene E. JOHANNESSEN ◽  
Sigrun L. KNARDAL ◽  
Inger Helene MADSHUS
1999 ◽  
Vol 337 (3) ◽  
pp. 599-606 ◽  
Author(s):  
Lene E. JOHANNESSEN ◽  
Sigrun L. KNARDAL ◽  
Inger Helene MADSHUS

DNA synthesis was inhibited in A431 cells by epidermal growth factor (EGF) in a p21/CIP1-dependent manner [where CIP1 is cyclin-dependent kinase (CDK)-interacting protein 1]. When 1 or 10 nM EGF was added, the level of p21/CIP1 was increased to the same extent, and the protein level peaked after approx. 5 h of incubation. The increase in p21/CIP1 mRNA upon addition of EGF was rapid, and was enhanced in the presence of cycloheximide. The half-life of p21/CIP1 mRNA in EGF-treated A431 cells was increased approx. 2-fold; this is in contrast with the case in MCF-7 cells with normal p53, in which the half-life of p21/CIP1 mRNA was not increased upon addition of EGF. This increased stability accounts for most of the increase in mRNA levels observed in A431 cells during short incubation periods. Additionally, upon prolonged incubation of A431 cells with EGF, the half-life of the protein was also increased compared with that in untreated cells and in cells treated with EGF for short time periods. Nuclear run-on assays demonstrated only marginal stimulation of transcription by 10 or 1 nM EGF, or by 10 ng/ml tumour necrosis factor α. Our results indicate that the most important mechanisms by which EGF increases p21/CIP1 protein levels in A431 cells are post-transcriptional and post-translational stabilization.


1990 ◽  
Vol 1052 (3) ◽  
pp. 453-460 ◽  
Author(s):  
Jos A.M. Berkers ◽  
Paul M.P. van Bergen en Henegouwen ◽  
Arie J. Verkleij ◽  
Johannes Boonstra

1992 ◽  
Vol 12 (12) ◽  
pp. 5816-5823
Author(s):  
D Park ◽  
S G Rhee

The 47-kDa protein coimmunoprecipitated with phospholipase C (PLC)-gamma 1 by anti-PLC-gamma 1 monoclonal antibodies is proved to be Nck, a protein composed almost exclusively of one SH2 and three SH3 domains. Nck and PLC-gamma 1 are recognized by certain anti-PLC-gamma 1 monoclonal antibodies because Nck and PLC-gamma 1 share an epitope that likely is located in their SH3 domains. Nck is widely distributed in rat tissues, with an especially high level of expression in testes. The expression levels of Nck remains unchanged during the development of rat brain, whereas PLC-gamma 1 decreases during the same developmental period. Stimulation of A431 cells with epidermal growth factor elicits the tight association of Nck with the epidermal growth factor receptor and phosphorylation of Nck on both serine and tyrosine residues. The phosphorylation of Nck is also enhanced in response to stimulation of the nerve growth factor receptor in PC12 cells, the T-cell receptor complex in Jurkat cells, the membrane immunoglobulin M in Daudi cells, and the low-affinity immunoglobulin G receptor (Fc gamma RII) in U937 cells. The phosphorylation of Nck was also enhanced following treatment of A431 cells with phorbol 12-myristate 13-acetate or forskolin. These results suggest that Nck is a target for a variety of protein kinases that might modulate the postulated role of Nck as an adaptor for the physical and functional coordination of signalling proteins.


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