Signal-dependent degradation of IkappaBalpha is mediated by an inducible destruction box that can be transferred to NF-kappaB, bcl-3 or p53.

AUTOR(ES)

Wulczyn, F G

RESUMO

Activation of the transcription factor NF-kappaB in response to a variety of stimuli is governed by the signal-induced proteolytic degradation of NF-kappaB inhibitor proteins, the IkappaBs. We have investigated the sequence requirements for signal-induced IkappaBalpha phosphorylation and proteolysis by generating chimeric proteins containing discrete sub-regions of IkappaBalpha fused to the IkappaBalpha homologue Bcl-3, the transcription factor NF-kappaB1/p50 and the tumour suppressor protein p53. Using this approach we show that the N-terminal signal response domain (SRD) of IkappaBalpha directs their signal-dependent phosphorylation and degradation when transferred to heterologous proteins. The C-terminal PEST sequence from IkappaBalpha was not essential for induced proteolysis of the chimeric proteins. A deletion analysis conducted on the SRD identified a 25 amino acid sub-domain of IkappaBalpha that is necessary and sufficient for the degradative response in vivo and for recognition by TNFalpha-dependent IkappaBalpha kinase in vitro . The results obtained should prove instrumental in the further characterization of IkappaB-specific kinases, as well as the E2 and E3 enzymes responsible for IkappaBalpha ubiquitination. Furthermore, they suggest a novel strategy for generating conditional mutants, by targetting heterologous proteins for transient elimination by the IkappaBalpha pathway.

Documentos Relacionados

• IkappaBalpha deficiency results in a sustained NF-kappaB response and severe widespread dermatitis in mice.
• Constitutive phosphorylation of IkappaBalpha by casein kinase II occurs preferentially at serine 293: requirement for degradation of free IkappaBalpha.
• Signal-induced degradation of I(kappa)B(alpha): association with NF-kappaB and the PEST sequence in I(kappa)B(alpha) are not required.
• Chronic human immunodeficiency virus type 1 infection of myeloid cells disrupts the autoregulatory control of the NF-kappaB/Rel pathway via enhanced IkappaBalpha degradation.
• Stress response decreases NF-kappaB nuclear translocation and increases I-kappaBalpha expression in A549 cells.