SCF(beta)(-TrCP) ubiquitin ligase-mediated processing of NF-kappaB p105 requires phosphorylation of its C-terminus by IkappaB kinase.
Processing of the p105 precursor to form the active subunit p50 of the NF-kappaB transcription factor is a unique case in which the ubiquitin system is involved in limited processing rather than in complete destruction of the target substrate. A glycine-rich region along with a downstream acidic domain have been demonstrated to be essential for processing. Here we demonstrate that following IkappaB kinase (IkappaK)-mediated phosphorylation, the C-terminal domain of p105 (residues 918-934) serves as a recognition motif for the SCF(beta)(-TrCP) ubiquitin ligase. Expression of IkappaKbeta dramatically increases processing of wild-type p105, but not of p105-Delta918-934. Dominant-negative beta-TrCP inhibits IkappaK-dependent processing. Furthermore, the ligase and wild-type p105 but not p105-Delta918-934 associate physically following phosphorylation. In vitro, SCF(beta)(-TrCP) specifically conjugates and promotes processing of phosphorylated p105. Importantly, the TrCP recognition motif in p105 is different from that described for IkappaBs, beta-catenin and human immunodeficiency virus type 1 Vpu. Since p105-Delta918-934 is also conjugated and processed, it appears that p105 can be recognized under different physiological conditions by two different ligases, targeting two distinct recognition motifs.
Orian
A
A
Department of Biochemistry and the Rappaport Institute for Research in the Medical Sciences, The Bruce Rappaport Faculty of Medicine, Haifa 31096, Israel.
Gonen
H
H
Bercovich
B
B
Fajerman
I
I
Eytan
E
E
Israël
A
A
Mercurio
F
F
Iwai
K
K
Schwartz
A L
AL
Ciechanover
A
A
D000255:Adenosine Triphosphate / Q000378:metabolism; D020816:Amino Acid Motifs; D000818:Animals; D019556:COS Cells; D002522:Chlorocebus aethiops; D006367:HeLa Cells; D006801:Humans; D051550:I-kappa B Kinase; D020672:I-kappa B Proteins / Q000378:metabolism; D046911:Macromolecular Substances; D016328:NF-kappa B / Q000378:metabolism*; D052002:NF-kappa B p50 Subunit; D010453:Peptide Synthases / Q000502:physiology*; D010766:Phosphorylation; D011498:Protein Precursors / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D017346:Protein Serine-Threonine Kinases / Q000502:physiology*; D017434:Protein Structure, Tertiary; D044843:SKP Cullin F-Box Protein Ligases; D014158:Transcription, Genetic
D020672:I-kappa B Proteins; D046911:Macromolecular Substances; D016328:NF-kappa B; D052002:NF-kappa B p50 Subunit; D011498:Protein Precursors; D000255:Adenosine Triphosphate; D044843:SKP Cullin F-Box Protein Ligases; D017346:Protein Serine-Threonine Kinases; C496559:CHUK protein, human; D051550:I-kappa B Kinase; C496560:IKBKB protein, human; C496565:IKBKE protein, human; D010453:Peptide Synthases