Ubiquitylated Tax targets and binds the IKK signalosome at the centrosome

Y Kfoury, R Nasr, A Favre-Bonvin, M El-Sabban… - Oncogene, 2008 - nature.com
Y Kfoury, R Nasr, A Favre-Bonvin, M El-Sabban, N Renault, ML Giron, N Setterblad…
Oncogene, 2008nature.com
Constitutive activation of the NF-κB pathway by the Tax oncoprotein plays a crucial role in
the proliferation and transformation of HTLV-I infected T lymphocytes. We have previously
shown that Tax ubiquitylation on C-terminal lysines is critical for binding of Tax to IκB kinase
(IKK) and its subsequent activation. Here, we report that ubiquitylated Tax is not associated
with active cytosolic IKK subunits, but binds endogenous IKK-α,-β,-γ, targeting them to the
centrosome. K63-ubiquitylated Tax colocalizes at the centrosome with IKK-γ, while K48 …
Abstract
Constitutive activation of the NF-κB pathway by the Tax oncoprotein plays a crucial role in the proliferation and transformation of HTLV-I infected T lymphocytes. We have previously shown that Tax ubiquitylation on C-terminal lysines is critical for binding of Tax to IκB kinase (IKK) and its subsequent activation. Here, we report that ubiquitylated Tax is not associated with active cytosolic IKK subunits, but binds endogenous IKK-α,-β,-γ, targeting them to the centrosome. K63-ubiquitylated Tax colocalizes at the centrosome with IKK-γ, while K48-ubiquitylated Tax is stabilized upon proteasome inhibition. Altogether, these results support a model in which K63-ubiquitylated Tax activates IKK in a centrosome-associated signalosome, leading to the production of Tax-free active cytoplasmic IKK. These observations highlight an unsuspected link between Tax-induced IKK activation and the centrosome.
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