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Biological sciences

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Site-specific phosphorylation of I(kappa)B(alpha) by a novel ubiquitination-dependent protein kinase activity

Article Abstract:

The Rel/NF-(kappa)B proteins act as transcriptional activators in the signal transduction pathways that connect extracellular signals to gene activation. In these pathways, activation of the transcription factor NF-(kappa)B involves phosphorylation of the inhibitor I(kappa)B(alpha), followed thereafter by proteolytic degradation. A key role is played by serine residues 32 and 36, which link I(kappa)B(alpha) to the ubiquitin-proteasome pathway. A multisubunit protein kinase also plays an important role as its ubiquitination is needed for phosphorylation of I(kappa)B(alpha) to proceed.

Ubiquitin, Chemical inhibitors

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Activation of the I-kappa-B-alpha kinase complex by MEKK1, a kinase of the JNK pathway

Article Abstract:

The mitogen-activated protein kinase/ERK kinase kinase-1 (MEKK1) was found to cause the site-specific phosphorylation of I-kappa-B-alpha, the inhibitor of the transcription factor NF-kappa-B, in vivo. It was also observed to directly activate the I-kappa-B-alpha kinase complex in vitro. Hence, MEKK1 is an essential component of both the c-Jun and NF-kappa-B stress response pathways. It may also be an integrator of multiple signal transduction pathways leading to the activation of NF-kappa-B.

Enzymes, Mitogens

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Tyrosine phosphorylation of IkappaB-alpha, activates NF-kappaB without proteolytic degradation of IkappaB-alpha

Article Abstract:

A novel pathway for the activation of transcription factor NF-kappaB was investigated in Jurkat leukemic T cells. Pervanadate-induced activation of the cells after inhibition of protein tyrosine phosphatases caused a dose-dependent increase in NF-kappaB-DNA binding activity in the cell nuclei. The reaction required the presence of T cell tyrosine kinase p56lck but was independent of protein kinase C.

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