The JNKK2-JNK1 Fusion Protein Acts As a Constitutively Active c-Jun Kinase That Stimulates c-Jun Transcription Activity (original) (raw)
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Genes & Development, 1994
The transcriptional activity of c-Jun is augmented through phosphorylation at two sites by a c-Jun amino-terminal kinase (JNK). All cells express two distinct JNK activities, 46 and 55 kD in size. It is not clear which of them is the more important c-Jun kinase and how they specifically recognize c-Jun. The 46-kD form of JNK was identified as a new member of the MAP kinase group of signal-transducing enzymes, JNK1. Here, we report the molecular cloning of the 55-kD form of JNK, JNK2, which exhibits 83% identity and similar regulation to JNK1. Despite this close similarity, the two JNKs differ greatly in their ability to interact with c-Jun. JNK2 binds c-Jun approximately 25 times more efficiently than JNK1, and as a result has a lower Km toward c-Jun than JNK1. The structural basis for this difference was investigated and traced to a small beta-strand-like region near the catalytic pocket of the enzyme. Modeling suggests that this region is solvent exposed and therefore is likely to serve as a docking site that increases the effective concentration of c-Jun near JNK2. These results explain how two closely related MAP kinases can differ in their ability to recognize specific substrates and thereby elicit different biological responses.
Molecular and cellular biology, 1999
The major components of the mitogen-activated protein kinase (MAPK) cascades are MAPK, MAPK kinase (MAPKK), and MAPKK kinase (MAPKKK). Recent rapid progress in identifying members of MAPK cascades suggests that a number of such signaling pathways exist in cells. To date, however, how the specificity and efficiency of the MAPK cascades is maintained is poorly understood. Here, we have identified a novel mouse protein, termed Jun N-terminal protein kinase (JNK)/stress-activated protein kinase-associated protein 1 (JSAP1), by a yeast two-hybrid screen, using JNK3 MAPK as the bait. Of the mammalian MAPKs tested (JNK1, JNK2, JNK3, ERK2, and p38alpha), JSAP1 preferentially coprecipitated with the JNKs in cotransfected COS-7 cells. JNK3 showed a higher binding affinity for JSAP1, compared with JNK1 and JNK2. In similar cotransfection studies, JSAP1 also interacted with SEK1 MAPKK and MEKK1 MAPKKK, which are involved in the JNK cascades. The regions of JSAP1 that bound JNK, SEK1, and MEKK1 ...
c-Jun N-terminal kinase (JNK) signaling: Recent advances and challenges
Biochimica et Biophysica Acta (BBA) - Proteins and Proteomics, 2010
c-Jun N-terminal kinase (JNK) ATP-competitive inhibitor ATP non-competitive inhibitor JNK structure JNK substrate Autophagy microRNA JNK knockout mouse c-Jun N-terminal kinases (JNKs), first characterized as stress-activated members of the mitogen-activated protein kinase (MAPK) family, have become a focus of inhibitor screening strategies following studies that have shown their critical roles in the development of a number of diseases, such as diabetes, neurodegeneration and liver disease. We discuss recent advances in the discovery and development of ATP-competitive and ATP-noncompetitive JNK inhibitors. Because understanding the modes of actions of these inhibitors and improving their properties will rely on a better understanding of JNK structure, JNK catalytic mechanisms and substrates, recent advances in these areas of JNK biochemistry are also considered. In addition, the use of JNK gene knockout animals is continuing to reveal in vivo functions for these kinases, with tissue-specific roles now being dissected with tissue-specific knockouts. These latest advances highlight the many challenges now faced, particularly in the directed targeting of the JNK isoforms in specific tissues.
Molecular and Cellular Biology, 2005
We report the identification and characterization of JAMP (JNK1 [Jun N-terminal kinase 1]-associated membrane protein), a predicted seven-transmembrane protein that is localized primarily within the plasma membrane and associates with JNK1 through its C-terminal domain. JAMP association with JNK1 outcompetes JNK1 association with mitogen-activated protein kinase phosphatase 5, resulting in increased and prolonged JNK1 activity following stress. Elevated expression of JAMP following UV or tunicamycin treatment results in sustained JNK activity and a higher level of JNK-dependent apoptosis. Inhibition of JAMP expression by RNA interference reduces the degree and duration of JNK activation and concomitantly the level of stress-induced apoptosis. Through its regulation of JNK1 activity, JAMP emerges as a membrane-anchored regulator of the duration of JNK1 activity in response to diverse stress stimuli.
Analysis of the Interaction between c-Jun and c-Jun N-terminal Kinase in Vivo
Journal of Biological Chemistry, 1998
Regulation of c-Jun transcriptional activity is believed to depend on a physical interaction with c-Jun N-terminal kinase (JNK) that facilitates signal-regulated phosphorylation of multiple regulatory phosphoacceptor sites within the activation domain. Here we have investigated the structural requirements and consequences of regulatory phosphorylation for the interaction between c-Jun and JNK in vivo. We show that binding of JNK to c-Jun in vivo does not require JNK catalytic activity or the presence of the potential phosphoacceptor sites within c-Jun and that JNK retains the capacity to bind to a pseudo-phosphorylated mutant of c-Jun where these sites are replaced by phospho-mimetic aspartic acid residues. The c-Jun delta region docking site is essential for interaction with JNK in vivo but is not sufficient, because a c-Jun mutant that retains this region but that lacks the C-terminal DNA-binding domain fails to interact. Experiments using purified recombinant c-Jun and JNK proteins show that the c-Jun DNA-binding domain harbors an auxiliary interaction domain that has the potential to bind to JNK independently. Our results suggest that JNK can be tethered passively to c-Jun in situ through multiple interacting regions and, when activated, can stimulate c-Jun phosphorylation without necessarily dissociating from its substrate. Auxiliary interactions mediated by the DNA-binding domain could play a role in targeting JNK preferentially to c-Jun in specific homo-or heterodimeric complexes.
Selective interaction of JNK protein kinase isoforms with transcription factors
The Embo Journal, 1996
The JNK protein kinase is a member of the MAP kinase group that is activated in response to dual phosphorylation on threonine and tyrosine. Ten JNK isoforms were identified in human brain by molecular cloning. These protein kinases correspond to alternatively spliced isoforms derived from the JNK1, JNK2 and JNK3 genes. The protein kinase activity of these JNK isoforms was measured using the transcription factors ATF2, Elk-i and members of the Jun family as substrates. Treatment of cells with interleukin-1 (IL-1) caused activation of the JNK isoforms. This activation was blocked by expression of the MAP kinase phosphatase MKP-1. Comparison of the binding activity of the JNK isoforms demonstrated that the JNK proteins differ in their interaction with ATF2, Elk-i and Jun transcription factors. Individual members of the JNK group may therefore selectively target specific transcription factors in vivo.
European Journal of Biochemistry, 2002
The CD53 antigen is a member of the tetraspanin membrane protein family that is expressed in the lymphoid-myeloid lineage. We have studied the implication of CD53 antigen in signal transduction by determining the effect of its ligation on the c-Jun N-terminal kinase (JNK) in different cell types. Ligation of the rat or human CD53 antigen induces a threeto fourfold transient activation of JNK activity that peaks at 3-5 min. The effect was detected by assaying the endogenous or exogenous (transfected) JNK activity. The JNK response was detected in IR938F cells, a rat B-cell lymphoma, and in Jurkat cells derived from a human T-cell lymphoma. This JNK activation was not mediated by the vav oncogene, and CD53 does not cooperate with CD3 for vav activation. A similar JNK activation was also detected in a human renal carcinoma cell line that was transiently transfected with the human CD53 cDNA to mimic the CD53 ectopic expression in carcinomas. In stable CD53-transfected cells it stimulated Jun-dependent transcriptional activity. We conclude that parts of the cell responses modulated by the CD53 are mediated by JNK activation, and this activation is independent of the different protein interactions that the CD53 protein has on specific cell types.