Mol. Cell. Biol., 12 1997, 7407-7416, Vol 17, No. 12
Z Wu, J Wu, E Jacinto and M Karin
At least three mitogen-activated protein kinase (MAPK) cascades were
identified in mammals, each consisting of a well-defined three-kinase
module composed of a MAPK, a MAPK kinase (MAPKK), and a MAPKK kinase
(MAPKKK). These cascades play key roles in relaying various physiological,
environmental, or pathological signals from the environment to the
transcriptional machinery in the nucleus. One of these MAPKs, c-Jun
N-terminal kinase (JNK), stimulates the transcriptional activity of c-Jun
in response to growth factors, proinflammatory cytokines, and certain
environmental stresses, such as short wavelength UV light or osmotic shock.
The JNKs are directly activated by the MAPKK JNKK1/SEK1/MKK4. However,
inactivation of the gene encoding this MAPKK by homologous recombination
suggested the existence of at least one more JNK-activating kinase.
Recently, the JNK cascade was found to be structurally and functionally
conserved in Drosophila, where DJNK is activated by the MAPKK DJNKK (hep).
By a database search, we identified an expressed sequence tag (EST)
encoding a portion of human MAPKK that is highly related to DJNKK (hep). We
used this EST to isolate a full-length cDNA clone encoding a human JNKK2.
We show that JNKK2 is a highly specific JNK kinase. Unlike JNKK1, it does
not activate the related MAPK, p38. Although the regulation of JNKK1
activities and that of JNKK2 activities could be very similar, the two
kinases may play somewhat different regulatory roles in a cell-type-
dependent manner.
Copyright © 1997, American Society for Microbiology
Molecular cloning and characterization of human JNKK2, a novel Jun NH2- terminal kinase-specific kinase
Department of Pharmacology, University of California, San Diego, La Jolla 92093-0636, USA.
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