Structure of an IκBα/NF-κB Complex

Abstract

The inhibitory protein, IkappaBalpha, sequesters the transcription factor, NF-kappaB, as an inactive complex in the cytoplasm. The structure of the IkappaBalpha ankyrin repeat domain, bound to a partially truncated NF-kappaB heterodimer (p50/ p65), has been determined by X-ray crystallography at 2.7 A resolution. It shows a stack of six IkappaBalpha ankyrin repeats facing the C-terminal domains of the NF-kappaB Rel homology regions. Contacts occur in discontinuous patches, suggesting a combinatorial quality for ankyrin repeat specificity. The first two repeats cover an alpha helically ordered segment containing the p65 nuclear localization signal. The position of the sixth ankyrin repeat shows that full-length IkappaBalpha will occlude the NF-kappaB DNA-binding cleft. The orientation of IkappaBalpha in the complex places its N- and C-terminal regions in appropriate locations for their known regulatory functions.

Copine-I represses NF-κB transcription by endoproteolysis of p65

“…This is supported by the observation that copine-I interacts with p65 between residues 1 and 286. Since IkBa binds to p65 across two domains (238-243 and 291-314) (Jacobs and Harrison, 1998), expression of IkBa probably prevents copine-I from binding to p65 through steric hindrance. However, we cannot rule out the possibility that cytosolic retention of p65 by IkBa aided the mechanisms protecting p65 from copine-I.…”

“…As observed before, copine-I effectively stimulated endoproteolysis of p65, however, cells expressing Myr-copine-I were less efficient (Figure 5b). Copine-I interacts with p65 across the RHD, which includes one of the two known IkBainteracting domains (238-243, Figure 3e; Jacobs and Harrison, 1998). Because of this, we investigated whether expression of IkBa could rescue Flag-p65 from endoproteolytic cleavage.…”

More complicated than it looks: assembly of Notch pathway transcription complexes

“…Burial of >1000 Å 2 is consistent with a high-affinity interaction. An apt comparison is the association between NF-kB, a Rel family transcription factor, and IkB, an ankyrin repeat protein, which forms a high-affinity complex with a K d B2.2 nM and buries B1400 Å 2 (Jacobs and Harrison, 1998;Bergqvist et al, 2006). On the other hand, the binding data for CSL-ANK complexes reported from multiple groups, clearly demonstrates that this interaction is weak to the point where it is almost unmeasurable.…”

Transcriptional complexes formed by NFAT dimers regulate the induction of T cell tolerance

“…Jurkat cells were transfected DNA contacts and is also involved in interactions with other transcription factors (13)(14)(15)(16)(17)(18). In resting T cells, NFAT proteins reside in the cytosol in a highly phosphorylated state.…”