Regulation of NF-κB2 p100 Processing by Its cis-Acting Domain

Guoliang Qing,Zhaoxia Qu,Gutian Xiao

doi:10.1074/jbc.m406619200

Guoliang Qing, Zhaoxia Qu + Show 1 more

Open Access

https://doi.org/10.1074/jbc.m406619200

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Abstract

Processing of NF-kappa B2 precursor protein p100 to generate p52 is tightly regulated. However, this proteolytic event could be actively induced by the NF-kappa B-inducing kinase and the human T-cell leukemia virus-encoded oncoprotein Tax or be constitutively turned on due to the loss of the C-terminal portion of p100. Whereas NF-kappa B-inducing kinase-mediated p100 processing requires beta-transducin repeat-containing protein, constitutive processing of p100 is independent of this protein. On the other hand, Tax-induced processing of p100 appears to be both beta-transducin repeat-containing protein-dependent and -independent. We show here that, besides the C-terminal sequences, multiple functional regions, including the two alpha-helices, dimerization domain, nuclear localization sequence, and glycine-rich region, located in the N terminus of p100, also play important roles in both constitutive and inducible processing, suggesting a common mechanism for p100 processing. We further demonstrate that with the help of the C-terminal death domain and I kappa B kinase alpha-targeting serines, the C-terminal ankyrin-repeat domain of p100 strongly interacts with its N-terminal dimerization domain and nuclear localization sequence, thereby bringing the C- and N-terminal sequences together to form a three-dimensional domain. This presumptive domain is not only responsible for suppression of constitutive processing but also required for inducible processing of p100. Taken together, these studies highlight the mechanism by which the different sequences within p100 work in concert to regulate its processing and shed light on the mechanisms of how p100 processing is tightly and delicately controlled.

Highlights

NF-␬B represents a family of dimeric transcription factors, which in mammals includes five members: RelA (p65), RelB, c-Rel, p50, and p52 [1,2,3]
We show that, unlike the C-terminal ankyrin repeat domain (ARD) and death domain (DD), which suppress p100 processing, multiple regions located in the N terminus of p100, such as the two ␣-helices, dimerization domain, nuclear localization sequences (NLS), and glycine-rich region (GRR), are important for both constitutive and inducible processing of p100
Multiple Domains within the p100 N Terminus Are Involved in p100 Processing Induced by NF-␬B-inducing kinase (NIK) or Tax— it is known that p100 C-terminal mutants, including ARD and DD deletion mutants, fail to respond to NIK- or Tax-induced processing [12, 14, 34, 35], the functional significance of the N-terminal domains of p100 in its inducible processing remains to be investigated

Summary

Introduction

NF-␬B represents a family of dimeric transcription factors, which in mammals includes five members: RelA (p65), RelB, c-Rel, p50, and p52 [1,2,3]. Unlike the three Rel proteins, which are directly synthesized as mature proteins, p50 and p52 are generated by proteolytic processing from their large precursors NF-␬B1 p105 and NF␬B2 p100, respectively [7, 8] Both p105 and p100 contain ankyrin repeats at their C-terminal regions and function as I␬B-like inhibitors of NF-␬B [9, 10]. Much progress on the regulation of p100 processing has been made recently, it is still unknown whether there is a general mechanism for both inducible and constitutive processing of p100 and whether the ␤-TrCP-independent mechanism of Tax-induced p100 processing involves p100 nuclear shuttling It is unknown why, unlike the IKK targeting serines within other proteins such as I␬B␣, the IKK␣-targeting serines in p100 are located at distant positions in the amino acid sequence [34, 35]

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