Constitutive JNK activation in NIH 3T3 fibroblasts induces a partially transformed phenotype.
The c-Jun N-terminal kinases (JNKs) (also known as stress-activated protein kinases or SAPKs), members of the mitogen-activated protein kinase (MAPK) family, regulate gene expression in response to a variety of physiological and unphysiological stimuli. Gene knockout experiments and the use of dominant interfering mutants have pointed to a role for JNKs in the processes of cell differentiation and survival as well as oncogenic transformation. Direct analysis of the transforming potential of JNKs has been hampered so far by the lack of constitutively active forms of these kinases. Recently, such mutants have become available by fusion of the MAPK with its direct upstream activator kinase. We have generated a constitutively active SAPK beta-MKK7 hybrid protein and, using this constitutively active kinase, we are able to demonstrate the transforming potential of activated JNK, which is weaker than that of classical oncogenes such as Ras or Raf. The inducible expression of SAPK beta-MKK7 caused morphological transformation of NIH 3T3 fibroblasts. Additionally, these cells formed small foci of transformed cells and grew anchorage-independent in soft agar. Furthermore, similar to oncogenic Ras and Raf, the expression of activated SAPK beta resulted in the disassembly of F-actin stress fibers. Our data suggest that constitutive JNK activation elicits major aspects of cellular transformation but is unable to induce the complete set of changes which are required to establish the fully transformed phenotype.
Rennefahrt
Ulrike E E
UE
Institut für Medizinische Strahlenkunde und Zellforschung, Universität Würzburg, 97078 Würzburg, Germany.
Illert
Bertram
B
Kerkhoff
Eugen
E
Troppmair
Jakob
J
Rapp
Ulf R
UR
D016475:3T3 Cells; D000199:Actins / Q000378:metabolism; D000818:Animals; D001483:Base Sequence; D002461:Cell Line, Transformed; D017931:DNA Primers; D018076:DNA, Complementary; D004789:Enzyme Activation; D005347:Fibroblasts / Q000201:enzymology; D048031:JNK Mitogen-Activated Protein Kinases; D048688:MAP Kinase Kinase 7; D051379:Mice; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D010641:Phenotype; D010766:Phosphorylation; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013347:Subcellular Fractions / Q000378:metabolism
D000199:Actins; D017931:DNA Primers; D018076:DNA, Complementary; D011993:Recombinant Fusion Proteins; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D048688:MAP Kinase Kinase 7; C482570:Map2k7 protein, mouse; D020929:Mitogen-Activated Protein Kinase Kinases