Targeted disruption of the MKK4 gene causes embryonic death, inhibition of c-Jun NH2-terminal kinase activation, and defects in AP-1 transcriptional activity.
MKK4 is a member of the mitogen-activated protein kinase kinase group of dual specificity protein kinases that functions as an activator of the c-Jun NH2-terminal kinase (JNK) in vitro. To examine the function of MKK4 in vivo, we investigated the effect of targeted disruption of the MKK4 gene. Crosses of heterozygous MKK4 (+/-) mice demonstrated that homozygous knockout (-/-) animals die before embryonic day 14, indicating that the MKK4 gene is required for viability. The role of MKK4 in JNK activation was examined by investigation of cultured MKK4 (+/+) and MKK4 (-/-) cells. Disruption of the MKK4 gene blocked JNK activation caused by: (i) the mitogen-activated protein kinase kinase kinase MEKK1, and (ii) treatment with anisomycin or heat shock. In contrast, JNK activation caused by other forms of environmental stress (UV-C radiation and osmotic shock) was partially inhibited in MKK4 (-/-) cells. Regulated AP-1 transcriptional activity, a target of the JNK signal transduction pathway, was also selectively blocked in MKK4 (-/-) cells. Complementation studies demonstrated that the defective AP-1 transcriptional activity was restored by transfection of MKK4 (-/-) cells with an MKK4 expression vector. These data establish that MKK4 is a JNK activator in vivo and demonstrate that MKK4 is an essential component of the JNK signal transduction pathway.
Yang
D
D
Howard Hughes Medical Institute, University of Massachusetts Medical School, Worcester 01605, USA.
Tournier
C
C
Wysk
M
M
Lu
H T
HT
Xu
J
J
Davis
R J
RJ
Flavell
R A
RA
D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D005314:Embryonic and Fetal Development / Q000235:genetics*; D004789:Enzyme Activation; D005804:Genes, Lethal; D006579:Heterozygote; D006720:Homozygote; D048031:JNK Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D051379:Mice; D018345:Mice, Knockout; D020929:Mitogen-Activated Protein Kinase Kinases; D020928:Mitogen-Activated Protein Kinases; D017346:Protein Serine-Threonine Kinases / Q000235:genetics*; D011505:Protein-Tyrosine Kinases / Q000235:genetics*; D018808:Transcription Factor AP-1 / Q000378:metabolism*
D018808:Transcription Factor AP-1; D011505:Protein-Tyrosine Kinases; D017346:Protein Serine-Threonine Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; C482562:Map2k4 protein, mouse; D020929:Mitogen-Activated Protein Kinase Kinases